(https://jknightandkarr.altervista.org/Computers/zx81-schematic-1.png)
https://jknightandkarr.altervista.org/Computers/zx81-schematic-1.png (https://jknightandkarr.altervista.org/Computers/zx81-schematic-1.png)
Well, starting post here on repairing my Timex Sinclair 1000. So here is the schematics. I replaced my NPN transistor, still nothing on the screen at all. I busted out the probes for my GW Instek GOS-620 and probed around aling with using my EEVBlog 121GW DMM and I have the folowing results:
-Tested the transistor with my cheap-o LCR meter, showed good, replaced unknown status NPN.
-Last night, changed the input signal on the composite circuit to the correct wire. I traced, from the ULA pin 16, through D9 and R32 which goes into the RF modulator.
-Hooking the scope to the Pin 16, yielded no results, so I used the 121GW, which has a Hz function, Pin 16, a signal, and 5v DC voltage.
-Input signal wire on mod = nothing, 5v DC and no Hz.
-Input side of D9 = said previous measurments.
-Output side of D9 = 5v DC and no Hz.
Needless to say, I didn't check anything on R32. Going by that there's a wire on the UK side, I might try the signal inpit wire on that pin, once I locate it..
As for D9 since the freq vanished there and even though theres 5v out, could the diode be the issue or should I just locate the UK straight from Pin 16 and use that?? Obviously the US side is supposed to have a freq of somekind going into the RF box, and my scope shows NOTHING other then the 5v increase. Suggestions? I have seen mods I can buy and have concidered them.
Quote from: JKnightandKARR on Jan 02, 2026, 01:44 PM-Output side of D9 = 5v DC and no Hz.
Needless to say, I didn't check anything on R32. Going by that there's a wire on the UK side, I might try the signal inpit wire on that pin, once I locate it..
As for D9 since the freq vanished there and even though theres 5v out, could the diode be the issue or should I just locate the UK straight from Pin 16 and use that?? Obviously the US side is supposed to have a freq of somekind going into the RF box, and my scope shows NOTHING other then the 5v increase. Suggestions? I have seen mods I can buy and have concidered them.
Are there any electrolytic caps inside this unit.
Anything over 15 years old, the first thing I do (before
ever powering it up) is replace any electrolytic caps. They can leak or dry up and then they no longer work as they're supposed to.
Quote from: JKnightandKARR on Jan 02, 2026, 01:44 PMusing my EEVBlog 121GW DMM and I have the folowing results:
I can't be the
only one to see 121GW and immediately see the connection, am I?!? Please tell me that relates to what I
think it relates to.
Quote from: Chris Savage on Jan 02, 2026, 08:00 PMQuote from: JKnightandKARR on Jan 02, 2026, 01:44 PM-Output side of D9 = 5v DC and no Hz.
Needless to say, I didn't check anything on R32. Going by that there's a wire on the UK side, I might try the signal inpit wire on that pin, once I locate it..
As for D9 since the freq vanished there and even though theres 5v out, could the diode be the issue or should I just locate the UK straight from Pin 16 and use that?? Obviously the US side is supposed to have a freq of somekind going into the RF box, and my scope shows NOTHING other then the 5v increase. Suggestions? I have seen mods I can buy and have concidered them.
Are there any electrolytic caps inside this unit. Anything over 15 years old, the first thing I do (before ever powering it up) is replace any electrolytic caps. They can leak or dry up and then they no longer work as they're supposed to.
Quote from: JKnightandKARR on Jan 02, 2026, 01:44 PMusing my EEVBlog 121GW DMM and I have the folowing results:
I can't be the only one to see 121GW and immediately see the connection, am I?!? Please tell me that relates to what I think it relates to.
It's got some caps, but none between the ULA and my composite mod. I probed the Z80 and the ULA and they seam to be doing something.
As far as 121GW, NO idea what you mean other then this: https://eevblog.store/products/121gw-multimeter (https://eevblog.store/products/121gw-multimeter)
Quote from: Chris Savage on Jan 02, 2026, 08:00 PMI can't be the only one to see 121GW and immediately see the connection, am I?!? Please tell me that relates to what I think it relates to.
Quote from: JKnightandKARR on Jan 02, 2026, 08:10 PMAs far as 121GW, NO idea what you mean other then this: https://eevblog.store/products/121gw-multimeter (https://eevblog.store/products/121gw-multimeter)
That's the meter that you use to measure lightning - 1.21 jigawatts. ;D :P
Quote from: granz on Jan 02, 2026, 09:34 PMThat's the meter that you use to measure lightning - 1.21 jigawatts. ;D :P
Thank you, granz for getting it!
Quote from: granz on Jan 02, 2026, 09:34 PMQuote from: Chris Savage on Jan 02, 2026, 08:00 PMI can't be the only one to see 121GW and immediately see the connection, am I?!? Please tell me that relates to what I think it relates to.
Quote from: JKnightandKARR on Jan 02, 2026, 08:10 PMAs far as 121GW, NO idea what you mean other then this: https://eevblog.store/products/121gw-multimeter (https://eevblog.store/products/121gw-multimeter)
That's the meter that you use to measure lightning - 1.21 jigawatts. ;D :P
Quote from: Chris Savage on Jan 02, 2026, 09:37 PMQuote from: granz on Jan 02, 2026, 09:34 PMThat's the meter that you use to measure lightning - 1.21 jigawatts. ;D :P
Thank you, granz for getting it!
Got ya. Am tired n feeling blah tonight..
Awwww man..... my BNC to BNC cable broke... I can't connect my analog scope to the freq counter...
Quote from: JKnightandKARR on Jan 03, 2026, 03:28 PMAwwww man..... my BNC to BNC cable broke... I can't connect my analog scope to the freq counter...
What are you trying to do?
Quote from: Chris Savage on Jan 05, 2026, 10:01 AMQuote from: JKnightandKARR on Jan 03, 2026, 03:28 PMAwwww man..... my BNC to BNC cable broke... I can't connect my analog scope to the freq counter...
What are you trying to do?
Had the Freq counter hooked to my analog scope, but end broken
Quote from: JKnightandKARR on Jan 05, 2026, 10:46 AMHad the Freq counter hooked to my analog scope, but end broken
I apologize...what I meant was...why did you need to connect the scope to the freqency counter?
Quote from: Chris Savage on Jan 05, 2026, 10:01 AMQuote from: JKnightandKARR on Jan 03, 2026, 03:28 PMAwwww man..... my BNC to BNC cable broke... I can't connect my analog scope to the freq counter...
What are you trying to do?
Had the Freq counter hooked to my analog scope, but end broken
Quote from: Chris Savage on Jan 05, 2026, 11:34 AMQuote from: JKnightandKARR on Jan 05, 2026, 10:46 AMHad the Freq counter hooked to my analog scope, but end broken
I apologize...what I meant was...why did you need to connect the scope to the freqency counter?
I hooked it up to get reding freq from the analog scope easier to read.
Well I hooked both up to a CRT n nada from both, so guess replace the regulators and caps to start with. Also have seen ULA or whatever they are called, that use modern parts, probly PLA, and go from there.
https://jknightandkarr.altervista.org/Computers/VISTA_Newsletter_v3_n5_OCR.pdf (https://jknightandkarr.altervista.org/Computers/VISTA_Newsletter_v3_n5_OCR.pdf)
Another schematic
Quote from: JKnightandKARR on Jan 07, 2026, 01:45 PMAnother schematic
I wanted to go over what I covered on the phone so when you reply with your findings, people aren't confused. I previously mentioned replacing ALL electrolytic caps in the system. But in today's conversation I mentioned the following next steps to confirm functionality:
- Verify DC voltage at the Z80 CPU (PIN 11) using your multimeter on DC voltage. Should be ~5.0VDC and then switch to AC to measure any ripple voltage, looking for excessive noise.
- Verify the clock pulse at PIN 6 on the Z80 CPU. By using a digital scope you can see the waveform and measure the frequency at the same time, which should be ~3.25MHz.
- Verify the output of the /M1 line on the Z80 CPU (PIN 27). By using a digital scope you can see the waveform and measure the frequency. The /M1 line should have activity if the Z80 CPU is executing instructions.
Many digital scopes have a USB port which can be used for screenshots of what you're measuring. If you can do this for the clock and /M1 signals, please post them for analysis.
Quote from: Chris Savage on Jan 07, 2026, 02:35 PMQuote from: JKnightandKARR on Jan 07, 2026, 01:45 PMAnother schematic
I wanted to go over what I covered on the phone so when you reply with your findings, people aren't confused. I previously mentioned replacing ALL electrolytic caps in the system. But in today's conversation I mentioned the following next steps to confirm functionality:
- Verify DC voltage at the Z80 CPU (PIN 11) using your multimeter on DC voltage. Should be ~5.0VDC and then switch to AC to measure any ripple voltage, looking for excessive noise.
- Verify the clock pulse at PIN 6 on the Z80 CPU. By using a digital scope you can see the waveform and measure the frequency at the same time, which should be ~3.25MHz.
- Verify the output of the /M1 line on the Z80 CPU (PIN 27). By using a digital scope you can see the waveform and measure the frequency. The /M1 line should have activity if the Z80 CPU is executing instructions.
Many digital scopes have a USB port which can be used for screenshots of what you're measuring. If you can do this for the clock and /M1 signals, please post them for analysis.
Thanks Chris, will do!
https://github.com/ikjordan/picozx81?tab=readme-ov-file (https://github.com/ikjordan/picozx81?tab=readme-ov-file)
I did find this, which does involves multiple platforms one of which is the Raspberry Pi Pico. If I make one of these, might try n add the expansion port.
(https://jknightandkarr.altervista.org/Computers/PowerSupply.jpg)
https://jknightandkarr.altervista.org/Computers/PowerSupply.jpg (https://jknightandkarr.altervista.org/Computers/PowerSupply.jpg)
Power Supply at the jack.
(https://jknightandkarr.altervista.org/Computers/5v_card.jpg)
https://jknightandkarr.altervista.org/Computers/5v_card.jpg (https://jknightandkarr.altervista.org/Computers/5v_card.jpg)
5V @ the card edge connector. Verified, 5v
(https://jknightandkarr.altervista.org/Computers/9v_A.jpg)
https://jknightandkarr.altervista.org/Computers/9v_A.jpg (https://jknightandkarr.altervista.org/Computers/9v_A.jpg)
(https://jknightandkarr.altervista.org/Computers/9V_B.jpg)
https://jknightandkarr.altervista.org/Computers/9V_B.jpg (https://jknightandkarr.altervista.org/Computers/9V_B.jpg)
Couple of shots of the 9V at the card edge connector. Kinda messy..
(https://jknightandkarr.altervista.org/Computers/M1.jpg)
https://jknightandkarr.altervista.org/Computers/M1.jpg (https://jknightandkarr.altervista.org/Computers/M1.jpg)
M1 at the card edge connector. Freq = 810 Khz.
(https://jknightandkarr.altervista.org/Computers/Pin6.jpg)
https://jknightandkarr.altervista.org/Computers/Pin6.jpg (https://jknightandkarr.altervista.org/Computers/Pin6.jpg)
Pin 6. 3.25 Mhz
(https://jknightandkarr.altervista.org/Computers/Pin11.jpg)
https://jknightandkarr.altervista.org/Computers/Pin11.jpg (https://jknightandkarr.altervista.org/Computers/Pin11.jpg)
(https://jknightandkarr.altervista.org/Computers/PIN11_scope.jpg)
https://jknightandkarr.altervista.org/Computers/PIN11_scope.jpg (https://jknightandkarr.altervista.org/Computers/PIN11_scope.jpg)
Pin 11 DMM Vs Scope.... UNKNOWN why meter voltage is diff from the Scope measure, which was 5v..... DMM showed no AC voltage.
(https://jknightandkarr.altervista.org/Computers/7805.jpg)
https://jknightandkarr.altervista.org/Computers/7805.jpg (https://jknightandkarr.altervista.org/Computers/7805.jpg)
Temp at the voltage regulator
(https://jknightandkarr.altervista.org/Computers/Z80.jpg)
https://jknightandkarr.altervista.org/Computers/Z80.jpg (https://jknightandkarr.altervista.org/Computers/Z80.jpg)
Z80 Temp
Well, I mean your 5V, Φ and /M1 signals look good. So it would seem the Z80 is running.
Quote from: Chris Savage on Jan 09, 2026, 09:11 AMWell, I mean your 5V, Φ and /M1 signals look good. So it would seem the Z80 is running.
Yeah, but the Pin 11 reading dmm vs scope confuses me.... maybe retest later with diff meter.. on the heat thing. I think I'll upgrade that 7805 to the upgraded part... burnt myself last night.
Quote from: JKnightandKARR on Jan 09, 2026, 12:50 PMYeah, but the Pin 11 reading dmm vs scope confuses me.... maybe retest later with diff meter.. on the heat thing. I think I'll upgrade that 7805 to the upgraded part... burnt myself last night.
As an electrician who has worked with high voltages, there's a principle called, "LIVE-DEAD-LIVE" testing. It's a way to confirm that a circuit is shut down and safe to work on. What if you were working on 480VAC and your meter measured no voltage? You might work on the circuit and it may actually be live, but perhaps your meter had a blown fuse or bad probe / lead. Using a proving unit, you prove that the meter can detect 480VAC, then you check the circuit under test, then you check the proving unit again to confirm the meter is working. Safety first.
But at lower voltages, you can use this same principle to confirm that the meter is working properly. In your case you weren't detecting voltage at the CPU pin, but the question is, could you detect voltage using that same meter from other points? One of my power supplies has lugs with multiple voltages at the outputs (3.3V, 5V, 9V, 12V) and I will often confirm voltages at these posts before testing a circuit.
Quote from: Chris Savage on Jan 09, 2026, 03:45 PMQuote from: JKnightandKARR on Jan 09, 2026, 12:50 PMYeah, but the Pin 11 reading dmm vs scope confuses me.... maybe retest later with diff meter.. on the heat thing. I think I'll upgrade that 7805 to the upgraded part... burnt myself last night.
As an electrician who has worked with high voltages, there's a principle called, "LIVE-DEAD-LIVE" testing. It's a way to confirm that a circuit is shut down and safe to work on. What if you were working on 480VAC and your meter measured no voltage? You might work on the circuit and it may actually be live, but perhaps your meter had a blown fuse or bad probe / lead. Using a proving unit, you prove that the meter can detect 480VAC, then you check the circuit under test, then you check the proving unit again to confirm the meter is working. Safety first.
But at lower voltages, you can use this same principle to confirm that the meter is working properly. In your case you weren't detecting voltage at the CPU pin, but the question is, could you detect voltage using that same meter from other points? One of my power supplies has lugs with multiple voltages at the outputs (3.3V, 5V, 9V, 12V) and I will often confirm voltages at these posts before testing a circuit.
The meter is fine along with probes. I probed multiple spots n got readings from them, just not much from there, and that was after the DC and AC measurments. Infact, pin 11 came before pin 6.
Quote from: JKnightandKARR on Jan 09, 2026, 07:31 PMThe meter is fine along with probes. I probed multiple spots n got readings from them, just not much from there, and that was after the DC and AC measurments. Infact, pin 11 came before pin 6.
I have three types of probes for my multimeters (not counting temp, current, etc).
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/662/TL75.jpg?hidebanner=true)
The standard probes that come with it, which are great for AC wall outlets, fuse boxes and automotive use. These don't work well for probing electronics component leads because they're bulky and not very "pointy".
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/847/MFG_TL175.jpg?hidebanner=true)
I also have CAT III / IV probes, which are for high voltages and also have a sheath that can cover the probes to prevent a short.
But the one I use for probing electronics are pin probes.
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/4843/MFG_501_6275.jpg?hidebanner=true)
These pin probes tend to make a better connection to leads on electronics components, having a needle-like tip that can even penetrate solder and insulation.
Quote from: Chris Savage on Jan 09, 2026, 10:18 PMQuote from: JKnightandKARR on Jan 09, 2026, 07:31 PMThe meter is fine along with probes. I probed multiple spots n got readings from them, just not much from there, and that was after the DC and AC measurments. Infact, pin 11 came before pin 6.
I have three types of probes for my multimeters (not counting temp, current, etc).
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/662/TL75.jpg?hidebanner=true)
The standard probes that come with it, which are great for AC wall outlets, fuse boxes and automotive use. These don't work well for probing electronics component leads because they're bulky and not very "pointy".
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/847/MFG_TL175.jpg?hidebanner=true)
I also have CAT III / IV probes, which are for high voltages and also have a sheath that can cover the probes to prevent a short.
But the one I use for probing electronics are pin probes.
(https://mm.digikey.com/Volume0/opasdata/d220001/medias/images/4843/MFG_501_6275.jpg?hidebanner=true)
These pin probes tend to make a better connection to leads on electronics components, having a needle-like tip that can even penetrate solder and insulation.
https://eevblog.store/products/brymen-bl21s2-t4sc-gold-plated-silicone-test-probes (https://eevblog.store/products/brymen-bl21s2-t4sc-gold-plated-silicone-test-probes)
This is what i got along with a similar pair that has coveres like yours do that cover all but the tips. I'll remeasure with all 3 of my meters to see what happens.
Quote from: JKnightandKARR on Jan 09, 2026, 10:35 PMI'll remeasure with all 3 of my meters to see what happens.
Did the other meters give you different readings?
While we're on the subject, what's the scope view of the video output?
Quote from: Chris Savage on Jan 11, 2026, 09:55 PMQuote from: JKnightandKARR on Jan 09, 2026, 10:35 PMI'll remeasure with all 3 of my meters to see what happens.
Did the other meters give you different readings?
While we're on the subject, what's the scope view of the video output?
I haven't had the time to mess with it, work been sucky n I'm too tired to care about anything at the moment... but will do it soon.
Quote from: JKnightandKARR on Jan 11, 2026, 11:31 PMI haven't had the time to mess with it, work been sucky n I'm too tired to care about anything at the moment... but will do it soon.
No problem. I understand. It's just that, while we are exploring alternative options for you on the Z80 front, I would like to see you get this classic (vintage) computer working, if possible.
Also, related to this: Brian (AKA @MicroNut) has (had?) a ZX-81 remake. He brought it to a retro-computing show that I put on at our local library. If I remember right, he had a digital "cassette tape" system that connected to the Sinclair's tape interface. Maybe he can give some information about his system.
Quote from: granz on Jan 12, 2026, 03:55 PMAlso, related to this: Brian (AKA @MicroNut) has (had?) a ZX-81 remake.
Define: remake?
Quote from: Chris Savage on Jan 12, 2026, 04:44 PMQuote from: granz on Jan 12, 2026, 03:55 PMAlso, related to this: Brian (AKA @MicroNut) has (had?) a ZX-81 remake.
Define: remake?
i've been doing research n you can get parts to make all new systems.
Quote from: JKnightandKARR on Jan 12, 2026, 06:51 PMi've been doing research n you can get parts to make all new systems.
If you're talking about the Minstrel Issue 3 Sinclair ZX81-Compatible Microcomputer Kit (https://www.hackster.io/news/tynemouth-software-launches-minstrel-issue-3-sinclair-zx81-compatible-microcomputer-kit-627bb602863b), I've posted about these before, but didn't think it was an exact replacement, but rather a clone using some updated parts.
(https://hackster.imgix.net/uploads/attachments/1026338/image_U5I2XJDrgB.png)
I was going to order one of these last year, but the the tariff thing ruined that.
Quote from: Chris Savage on Jan 12, 2026, 08:00 PMQuote from: JKnightandKARR on Jan 12, 2026, 06:51 PMi've been doing research n you can get parts to make all new systems.
If you're talking about the Minstrel Issue 3 Sinclair ZX81-Compatible Microcomputer Kit (https://www.hackster.io/news/tynemouth-software-launches-minstrel-issue-3-sinclair-zx81-compatible-microcomputer-kit-627bb602863b), I've posted about these before, but didn't think it was an exact replacement, but rather a clone using some updated parts.
(https://hackster.imgix.net/uploads/attachments/1026338/image_U5I2XJDrgB.png)
I was going to order one of these last year, but the the tariff thing ruined that.
One i know of was ZX81 +38 or something like that
Quote from: JKnightandKARR on Jan 12, 2026, 09:58 PMOne i know of was ZX81 +38 or something like that
I was going to order this one (https://www.tindie.com/products/tynemouth/minstrel-3-with-keyboard-z80-based-zx81-kit/), but as you can see, shipping to the U.S.
starts at $50.00!!!
Quote from: Chris Savage on Jan 12, 2026, 10:52 PMQuote from: JKnightandKARR on Jan 12, 2026, 09:58 PMOne i know of was ZX81 +38 or something like that
I was going to order this one (https://www.tindie.com/products/tynemouth/minstrel-3-with-keyboard-z80-based-zx81-kit/), but as you can see, shipping to the U.S. starts at $50.00!!!
Order that with the sockets for the chips! Only an additional $50.... lol kinda $$$$$$ can buy an original for 1/4 cost
Quote from: Chris Savage on Jan 12, 2026, 10:52 PMQuote from: JKnightandKARR on Jan 12, 2026, 09:58 PMOne i know of was ZX81 +38 or something like that
I was going to order this one (https://www.tindie.com/products/tynemouth/minstrel-3-with-keyboard-z80-based-zx81-kit/), but as you can see, shipping to the U.S. starts at $50.00!!!
https://github.com/mahjongg2 (https://github.com/mahjongg2)
I found this, idk if this looks interesting to you or not, beats $250... lol
Edit: Here's what looks like original PCB of the ZX-81
https://github.com/Bluescreen2001/ZX81-PCB/tree/main/ZX81_keyboard (https://github.com/Bluescreen2001/ZX81-PCB/tree/main/ZX81_keyboard)
Quote from: Chris Savage on Jan 12, 2026, 04:44 PMQuote from: granz on Jan 12, 2026, 03:55 PMAlso, related to this: Brian (AKA @MicroNut) has (had?) a ZX-81 remake.
Define: remake?
A modern remake of the old ZX-81. There are several (one of them is here: https://www.hackup.net/2022/01/building-a-new-zx81-computer/ (https://www.hackup.net/2022/01/building-a-new-zx81-computer/).) I don't remember which one Brian had, as that show was many years ago. That is why I tagged Brian, I was hoping that he could pitch in.
Quote from: JKnightandKARR on Jan 12, 2026, 11:51 PMOrder that with the sockets for the chips! Only an additional $50.... lol kinda $$$$$$ can buy an original for 1/4 cost
Yeah, I did think the $50.00 for extra sockets was a bit much. Of course, the modernized versions don't require an old TV to get video.
Quote from: granz on Jan 13, 2026, 06:57 AMA modern remake of the old ZX-81. There are several (one of them is here:
I don't think tagging works on SMF. :-\ That PCB looks like the one JKnightandKARR (https://savagechats.com/index.php?action=profile;u=4) linked. Mahjongg?
The remake that Granz was mentioning that I had was a DE0-Nano FPGA board with a ZX81 softcore called ZXGate I found on the internet. The "cassette" was an Arduino Due which had a TFT screen and a SD card reader. Sadly I lost the code for the Arduino but I also made a "cassette" with a Propeller 1, SD card reader and a serial 16x2 LCD. I no longer have that code either. :(
The cassette remake is just reading an SD card and then bit banging pulses based on each bit of each byte. Once the timing is determined and using a 3.3V output you can feed it into the "mic" jack. It wouldn't be too hard to replicate it again and I found that it is more reliable than the actual cassette system.
I also have 2 TS1000s, a US ZX81 and the ZXMore kit (can also do ZX80) that is no longer available.
Thanks Brian, I was pretty sure (>99%) that you had a TS-1000 clone, but I forgot that it was an FPGA system. I also think that I have a DE-0 system somewhere, that I inherited when Peter moved out.
By the way - did you get an email alert from my tagging you, or did you just happen to log in and see the posts?
Quote from: Chris Savage on Jan 13, 2026, 10:22 AMQuote from: JKnightandKARR on Jan 12, 2026, 11:51 PMOrder that with the sockets for the chips! Only an additional $50.... lol kinda $$$$$$ can buy an original for 1/4 cost
Yeah, I did think the $50.00 for extra sockets was a bit much. Of course, the modernized versions don't require an old TV to get video.
Just alittle bit... lol
Quote from: MicroNut on Jan 13, 2026, 03:15 PMThe remake that Granz was mentioning that I had was a DE0-Nano FPGA board with a ZX81 softcore called ZXGate I found on the internet. The "cassette" was an Arduino Due which had a TFT screen and a SD card reader. Sadly I lost the code for the Arduino but I also made a "cassette" with a Propeller 1, SD card reader and a serial 16x2 LCD. I no longer have that code either. :(
The cassette remake is just reading an SD card and then bit banging pulses based on each bit of each byte. Once the timing is determined and using a 3.3V output you can feed it into the "mic" jack. It wouldn't be too hard to replicate it again and I found that it is more reliable than the actual cassette system.
I also have 2 TS1000s, a US ZX81 and the ZXMore kit (can also do ZX80) that is no longer available.
That'd be VERY handy! I'd like one if one can be recreated.
Quote from: Chris Savage on Jan 13, 2026, 10:25 AMQuote from: granz on Jan 13, 2026, 06:57 AMA modern remake of the old ZX-81. There are several (one of them is here:
I don't think tagging works on SMF. :-\ That PCB looks like the one JKnightandKARR (https://savagechats.com/index.php?action=profile;u=4) linked. Mahjongg?
Did you see the files I posted? I think original PCB designs, as well as new designs as you already saw, for the ZX=81 or Timex Sinclair 1000, seem that the 2 systems, even though technically the same, are somewhat different, at least as far as the RF boxes are concerned.
Granz, no I didn't see the alert.
JKKnightandCARR - sadly I lost all my ZX81 FPGA and Cassette source code when the external hard drive I had it on went bad. I do have the ZX-gate source though which is good since it is no longer on the net.
I'm thinking of redoing it. I know the ZX-Gate used a PS2 Keyboard and VGA output. When I used the DE0-Nano I tapped into the video output before the vga conversion and had to use a transistor driver to get the composite output. I now have a DE10-Lite which has a built in VGA and Arduino header with double the space of the Nano so I will do it on that instead. Once that is done it'll be easy to port it over to the Nano
I'll start a thread on the Projects category when I get it going so I won't hijack this thread.
Quote from: MicroNut on Jan 13, 2026, 11:00 PMGranz, no I didn't see the alert.
I've looked into mods for SMF that can do this, but the few I see don't look like they've been updated in years.
EDIT: Ironically, the manual says they're supported. I need to check on permissions. I will look into this now.
@Chris Savage I think I gotta place to start. Posted on the Vintage Computer Forum and was told to check Reset (Pin 26) which is active low, so 0v is expected. at the card edge connector, I am getting 5v, so here's the place to start I think.
Quote from: JKnightandKARR on Jan 22, 2026, 10:05 PM@Chris Savage
I think I gotta place to start. Posted on the Vintage Computer Forum and was told to check Reset (Pin 26) which is active low, so 0v is expected. at the card edge connector, I am getting 5v, so here's the place to start I think.
Reset is, as you mentioned, an active low signal. That means that when it is reading 0V, the CPU is in reset condition. When
Reset is +5V, then the CPU is
not in reset, and should be running properly.
Quote from: granz on Jan 22, 2026, 11:08 PMQuote from: JKnightandKARR on Jan 22, 2026, 10:05 PM@Chris Savage
I think I gotta place to start. Posted on the Vintage Computer Forum and was told to check Reset (Pin 26) which is active low, so 0v is expected. at the card edge connector, I am getting 5v, so here's the place to start I think.
Reset is, as you mentioned, an active low signal. That means that when it is reading 0V, the CPU is in reset condition. When Reset is +5V, then the CPU is not in reset, and should be running properly.
Ok, the VCF forums said it should be low. Probly replace all caps n go from there...
Quote from: JKnightandKARR on Jan 23, 2026, 01:12 AMOk, the VCF forums said it should be low. Probly replace all caps n go from there...
The VCF forums said the /RESET line should be LOW normally? That is incorrect. It should only be LOW for like a millisecond at power-up. After that it should remain HIGH. And it must be, since you already confirmed that the /M1 line was changing states, which indicates the Z80 is executing instructions. It couldn't do that if /RESET was LOW.
Quote from: Chris Savage on Jan 23, 2026, 09:11 AMQuote from: JKnightandKARR on Jan 23, 2026, 01:12 AMOk, the VCF forums said it should be low. Probly replace all caps n go from there...
The VCF forums said the /RESET line should be LOW normally? That is incorrect. It should only be LOW for like a millisecond at power-up. After that it should remain HIGH. And it must be, since you already confirmed that the /M1 line was changing states, which indicates the Z80 is executing instructions. It couldn't do that if /RESET was LOW.
Ok, then that's normal then. Rechecked n I missread the info..
(https://jknightandkarr.altervista.org/Computers/20260128_112338.jpg)
https://jknightandkarr.altervista.org/Computers/20260128_112338.jpg (https://jknightandkarr.altervista.org/Computers/20260128_112338.jpg)
Well, Hooked up my Rigol DS1194Z's Logic Analyzer up to D0-D3, saw no need to try all 8 data lines. Anyhow, the Z80 is clearly doing something, so thinking of picking up one of the more modern replacements, such as this: https://www.tindie.com/products/charlieingley/vla81-zx81-ula-replacement/ (https://www.tindie.com/products/charlieingley/vla81-zx81-ula-replacement/) since from my searching, the originals are prone to failure, so that's what I have so far.
So it appears that the issue is either in the video output, or the video input of your display.
Before you spend $33, plus S/H, have you tried swapping the ULA from the other TS1000? That may help (unless the other one is also dead - although it shouldn't cost you more than a bit of time to try it.)
Quote from: Chris Savage on Jan 28, 2026, 11:59 AMSo it appears that the issue is either in the video output, or the video input of your display.
My TV is fine, I been using the inputs for my Wii. I'll hook up my scope to pin 16 of the ULA n see what I get now that I have it figured out, shouldn't be my composite mod, iI replaced my transistor with one I tested with my LCR meter.
Quote from: granz on Jan 28, 2026, 12:59 PMBefore you spend $33, plus S/H, have you tried swapping the ULA from the other TS1000? That may help (unless the other one is also dead - although it shouldn't cost you more than a bit of time to try it.)
Can't hurt, however it didn't work either when I hooked up to. CRT tv. As I said above, probly hook up my scope to the ULA to see what I get.
Quote from: JKnightandKARR on Jan 28, 2026, 01:09 PMCan't hurt, however it didn't work either when I hooked up to. CRT tv.
Yeah, I was meaning that you could swap the ULAs and then try both computers; it is possible that one ULA, and the other TS-1000 may work. That would be a quick, easy way to test that.
Quote from: granz on Jan 28, 2026, 01:14 PMQuote from: JKnightandKARR on Jan 28, 2026, 01:09 PMCan't hurt, however it didn't work either when I hooked up to. CRT tv.
Yeah, I was meaning that you could swap the ULAs and then try both computers; it is possible that one ULA, and the other TS-1000 may work. That would be a quick, easy way to test that.
Yup.
(https://jknightandkarr.altervista.org/Computers/Ch2_ULA_Pin16.jpg)
https://jknightandkarr.altervista.org/Computers/Ch2_ULA_Pin16.jpg (https://jknightandkarr.altervista.org/Computers/Ch2_ULA_Pin16.jpg)
Not much here.
(https://jknightandkarr.altervista.org/Computers/Ch3_ULA_Pin16.jpg)
https://jknightandkarr.altervista.org/Computers/Ch3_ULA_Pin16.jpg (https://jknightandkarr.altervista.org/Computers/Ch3_ULA_Pin16.jpg)
WE HAVE A SIGNAL!!
(https://jknightandkarr.altervista.org/Computers/After_Trans.jpg)
https://jknightandkarr.altervista.org/Computers/After_Trans.jpg (https://jknightandkarr.altervista.org/Computers/After_Trans.jpg)
This is the signal after the transistor.
(https://jknightandkarr.altervista.org/Computers/RCA_Out.jpg)
https://jknightandkarr.altervista.org/Computers/RCA_Out.jpg (https://jknightandkarr.altervista.org/Computers/RCA_Out.jpg)
Output on the jack. Pretty much the same.
If I am guessing, which I am, I'd say my issue is the composite mod... I followed the directions, so either my NPN is fried, even though my cheap LCR meter says "We're Good" or something wrong with the design and it fried when turned it on... IDK... Guess buy a composite mod kit n go from there.
https://web.archive.org/web/20250123231729/https://www.bytedelight.com/?page_id=3560 (https://web.archive.org/web/20250123231729/https://www.bytedelight.com/?page_id=3560)
This is the circuit I used for the composite mod btw.
Well...... Pretty sure I figured out my problem, on one of the ZX-81s anyhow... Circuit above is the one I used. Now...... PROVIDING..... I could pay attention to what I was doing, I'd wire it as in the link.....
E-Output
B- Signal
C- 5V+
it MIGHT work..... Me:
E-Signal
B- 5v
C- Output
Need to pay more attention and not work on stuff when tired..... new transistor and will try again..... I think Bill Engval said it best...... HERE'S YOUR SIGN........
Well, it seems you may have figured it out. Let us know how it goes.
Quote from: Chris Savage on Feb 06, 2026, 09:38 PMWell, it seems you may have figured it out. Let us know how it goes.
Just guessing, but if the transistor was wired right, probly would have worked...
(https://jknightandkarr.altervista.org/Computers/screen.jpeg)https://jknightandkarr.altervista.org/Computers/screen.jpeg (https://jknightandkarr.altervista.org/Computers/screen.jpeg)
It's a start!!
Congrats, Joe! Hopefully you will get the rest worked out quickly.
Looks like, "POKE" and then some scribble. But, as
@granz said, it's a start. At least you know now that it's alive.
Quote from: granz on Feb 08, 2026, 08:52 PMCongrats, Joe! Hopefully you will get the rest worked out quickly.
Thanks. I'll probly replace that mod with one that'll work better.
Quote from: Chris Savage on Feb 08, 2026, 09:43 PMLooks like, "POKE" and then some scribble. But, as @granz said, it's a start. At least you know now that it's alive.
Yeah. The mod 1) didn't have power, and the 33 ohm resistor was killing the signal, so maybe it's not strong enough??
Quote from: JKnightandKARR on Feb 08, 2026, 09:56 PMYeah. The mod 1) didn't have power, and the 33 ohm resistor was killing the signal, so maybe it's not strong enough??
(https://blog.codesurfer.dev/content/images/size/w1000/2021/12/Screen-Shot-2021-12-28-at-1.51.12-PM.png)
So, I looked around on the internet and there is a lot of varied schematics, and even in the ones like yours, much variance in the values (https://blog.codesurfer.dev/zx81-timex-sinclair-1000-composite-video-mod/).
Many people who have taken this task on have expressed issues that they've had finding the right values (http://www.breakintoprogram.co.uk/computers/composite-video-modification-for-the-zx81) to get the signal they want. It seems there may also be a little bit of difference in the various displays and the signals they require.
As to your original question
and schematic. I was concerned when I saw the 100Ω resistor, since at 5V (minus the transistor voltage drop), you're looking at nearly 200mW of power consumption, which is the max of the 2N3904. Normally you wouldn't choose a transistor that is at the max of your electrical specs.
Quote from: Chris Savage on Feb 08, 2026, 10:57 PMQuote from: JKnightandKARR on Feb 08, 2026, 09:56 PMYeah. The mod 1) didn't have power, and the 33 ohm resistor was killing the signal, so maybe it's not strong enough??
(https://blog.codesurfer.dev/content/images/size/w1000/2021/12/Screen-Shot-2021-12-28-at-1.51.12-PM.png)
So, I looked around on the internet and there is a lot of varied schematics, and even in the ones like yours, much variance in the values (https://blog.codesurfer.dev/zx81-timex-sinclair-1000-composite-video-mod/).
Many people who have taken this task on have expressed issues that they've had finding the right values (http://www.breakintoprogram.co.uk/computers/composite-video-modification-for-the-zx81) to get the signal they want. It seems there may also be a little bit of difference in the various displays and the signals they require.
As to your original question and schematic. I was concerned when I saw the 100Ω resistor, since at 5V (minus the transistor voltage drop), you're looking at nearly 200mW of power consumption, which is the max of the 2N3904. Normally you wouldn't choose a transistor that is at the max of your electrical specs.
That circuit, better you think? I see 1 issue with mine with that documentation, is the ULA 2C184E vs ULA 2C210E. The ULA 2C210E has the back porch signal, the other doesn't, and mine is the 2C184E, so NO backporch signal. This might be part of the problem, according to the documentation.
EDIT: I found this http://zx.zigg.net/misc-projects/ZX81_Video_Conditioning.pdf?ref=blog.codesurfer.dev (http://zx.zigg.net/misc-projects/ZX81_Video_Conditioning.pdf?ref=blog.codesurfer.dev) This is what I need ain't it?
Once you get your TS working, you will want some books for it. I had several books, but these are my favorites:
(https://www.timexsinclair.com/wp-content/uploads/2020/04/The-ZX81-Companion-191x300.jpg)
http://[url="https://dn720002.ca.archive.org/0/items/the-zx-81-companion/The%20ZX81%20Companion_text.pdf"
This has a disassembly of the ZX-81's ROM in the back. I don't really remember much else than that, but I used mine so much that it got pretty dog-eared.
(https://www.timexsinclair.com/wp-content/uploads/2020/04/BytingTS1000-L-203x300.jpg)
https://www.amazon.com/Byteing-Deeper-into-Timex-Sinclair/dp/0471898880 (https://www.amazon.com/Byteing-Deeper-into-Timex-Sinclair/dp/0471898880) $16.73 + $4.49 S/H (Could not find this as a PDF.)
(https://www.technophile.one/wp-content/uploads/2022/01/Sinclair-ZX81-Manual-1.jpg)
https://www.historybit.it/wp-content/uploads/2018/09/ZX81_BasicProgramming.pdf (https://www.historybit.it/wp-content/uploads/2018/09/ZX81_BasicProgramming.pdf)
I was always captivated by the cover picture of the programming manual. It still grabs my attention.
(https://technonew.speccy.org/album/ref_card/images/ref_card_1_2_3_jpg.jpg)
https://www.scribd.com/document/323515982/zx80-81-refcard (https://www.scribd.com/document/323515982/zx80-81-refcard)
This was another well-used document from my ZX-81 days.
I don't remember having this (although I probably did get it with my kit,) but it may help:
https://k1.spdns.de/Vintage/Sinclair/80/Sinclair%20ZX81/Service%20and%20Assembly%20Manual/ZX81%20Service%20and%20Assembly%20Manual%20%28scans%29.pdf
Hope these help.
@granz Those books are definitely great. The reference card was well used by me. In my moves I lost it though. :( A couple of years ago Bean (on the Parallax forums) was selling his ZX81 books and the reference card was one of them. So I bought it and some other books. Some of them are the ones you mentioned.
Quote from: MicroNut on Feb 09, 2026, 09:36 AM@granz Those books are definitely great. The reference card was well used by me. In my moves I lost it though. :( A couple of years ago Bean (on the Parallax forums) was selling his ZX81 books and the reference card was one of them. So I bought it and some other books. Some of them are the ones you mentioned.
I had that reference card in my books, and carried it pretty much everywhere; that and
The ZX81 Companion. I actually had many more books about the ZX81, but those listed above were my favorites.
Quote from: granz on Feb 09, 2026, 10:33 AMQuote from: MicroNut on Feb 09, 2026, 09:36 AM@granz Those books are definitely great. The reference card was well used by me. In my moves I lost it though. :( A couple of years ago Bean (on the Parallax forums) was selling his ZX81 books and the reference card was one of them. So I bought it and some other books. Some of them are the ones you mentioned.
I had that reference card in my books, and carried it pretty much everywhere; that and The ZX81 Companion. I actually had many more books about the ZX81, but those listed above were my favorites.
I'll check those out, thanks. IK do have the manual and one for games I got with it. OK, I pulled the ULA from both of them, and did a swap. For ease I am calling the one I bought Mine/My, and the one Granz/His sent me as Granz. Anyhow, My ULA is the old ver so, no backporch signal, Granz has the newer ULA with the backporch signal. After the swap, Mine no longer has a picture and the input looses and regains the signal, so maybe the newer ULA is bad, so Will do a swap back, and go from there.
Quote from: JKnightandKARR on Feb 09, 2026, 11:45 AMAfter the swap, Mine no longer has a picture and the input looses and regains the signal, so maybe the newer ULA is bad, so Will do a swap back, and go from there.
Yep, sounds like the ULA in the system that I sent is no good. Like I said, I have/had no idea of the status of that computer.
Good troubleshooting work, Joe.
Quote from: granz on Feb 09, 2026, 11:48 AMQuote from: JKnightandKARR on Feb 09, 2026, 11:45 AMAfter the swap, Mine no longer has a picture and the input looses and regains the signal, so maybe the newer ULA is bad, so Will do a swap back, and go from there.
Yep, sounds like the ULA in the system that I sent is no good. Like I said, I have/had no idea of the status of that computer.
Good troubleshooting work, Joe.
Going to recheck the sockets and make sure it is seated correctly, also was GOING to try the one you sent since it has a working ULA on my other TV, though my VCR, but figures.... my VCR broke yesterday...
Quote from: MicroNut on Jan 13, 2026, 03:15 PMThe remake that Granz was mentioning that I had was a DE0-Nano FPGA board with a ZX81 softcore called ZXGate I found on the internet. The "cassette" was an Arduino Due which had a TFT screen and a SD card reader. Sadly I lost the code for the Arduino but I also made a "cassette" with a Propeller 1, SD card reader and a serial 16x2 LCD. I no longer have that code either. :(
The cassette remake is just reading an SD card and then bit banging pulses based on each bit of each byte. Once the timing is determined and using a 3.3V output you can feed it into the "mic" jack. It wouldn't be too hard to replicate it again and I found that it is more reliable than the actual cassette system.
I also have 2 TS1000s, a US ZX81 and the ZXMore kit (can also do ZX80) that is no longer available.
Just curious, but happen to know a good source of parts? I need a ULA w/backporch and preferably a composite mod with adjustable settings for image for each of my systems. I found one, but NO shipping to USA available...
Quote from: JKnightandKARR on Feb 26, 2026, 08:56 PMJust curious, but happen to know a good source of parts? I need a ULA w/backporch and preferably a composite mod with adjustable settings for image for each of my systems. I found one, but NO shipping to USA available...
At a glance I found the following...
Sinclair ZX81 / ZX80 / Timex 1000 - Composite Video with Backporch - Kit (https://ebay.us/m/NfRjBY)
Like the C=64, sometimes you have to buy bad units that are sold for parts. Doesn't guarantee you'll get the parts you need, but here are two examples.
Timex Sinclair 1000 Personal Computer (PARTS/NOT WORKING) -Not Tested- AS-IS- (https://ebay.us/m/O464Kf)
Timex Sinclair 1000 Personal Computer & 1016 RAM, UNTESTED For Parts (https://ebay.us/m/19idA5)
SellMyRetro in the UK sells a lot of ZX81 related items. They have VLA81 (a drop in modern replacement for the ULA) for sale https://www.sellmyretro.com/offer/details/vla81--_-sinclair-zx81-ula-replacement--_-new-63982 (https://www.sellmyretro.com/offer/details/vla81--_-sinclair-zx81-ula-replacement--_-new-63982).
Also I have been on a ZX81 forum with a wealth of info and friendly people ZX Sinclair World (https://www.sinclairzxworld.com/index.php)
With that seller being in New York, the shipping is as low as a very reasonable $5.
I found some useful stuff on Ebay, just need the $$. Thanks all.
@Chris Savage @granz or anyone else. How does this look for ULA??https://github.com/rodneyknaap/ZX81_ULA_ISSUE_5 (https://github.com/rodneyknaap/ZX81_ULA_ISSUE_5)
I don't know - it seems that it would be better to just buy a replacement (https://www.vretrodesign.com/products/vla81-zx81-ula-replacement - and it has 13 5-star reviews) rather than trying to build your own.
Plus it always bothers me when someone produces a document that has a large percentage dedicated to "not my fault" disclaimer legalese.
Quote from: granz on Apr 19, 2026, 09:58 PMI don't know - it seems that it would be better to just buy a replacement (https://www.vretrodesign.com/products/vla81-zx81-ula-replacement - and it has 13 5-star reviews) rather than trying to build your own.
Plus it always bothers me when someone produces a document that has a large percentage dedicated to "not my fault" disclaimer legalese.
Haven't found that site at all, I just get the one with no shipping to US available.... besides FleeBay. lol THANKS!
Glad to help. I hope that it helps get your Sinclair working.
Quote from: granz on Apr 19, 2026, 09:58 PMI don't know - it seems that it would be better to just buy a replacement (https://www.vretrodesign.com/products/vla81-zx81-ula-replacement - and it has 13 5-star reviews) rather than trying to build your own.
Plus it always bothers me when someone produces a document that has a large percentage dedicated to "not my fault" disclaimer legalese.
Do me a favor? Can you put in your info in there, like you was buying one, minus payment info, and see if it accepts your address? It says cannot ship to my address. Wonder if it's a terrif thing??
Yep, I'm getting the same:
QuoteShipping not available
Your order cannot be shipped to the selected address. Review your address to ensure it's correct and try again, or select a different address.
You are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
Quote from: granz on Apr 25, 2026, 03:33 PMYou are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
There are Tindie stores I have previously purchased from that are not shipping to the U.S. currently (some are in the U.K.) because of the tariff issues.
Quote from: granz on Apr 25, 2026, 03:33 PMYep, I'm getting the same:
QuoteShipping not available
Your order cannot be shipped to the selected address. Review your address to ensure it's correct and try again, or select a different address.
You are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
Quote from: Chris Savage on Apr 25, 2026, 09:40 PMQuote from: granz on Apr 25, 2026, 03:33 PMYou are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
There are Tindie stores I have previously purchased from that are not shipping to the U.S. currently (some are in the U.K.) because of the tariff issues.
Crap....... was hoping for $35 vs $50......
Quote from: granz on Apr 25, 2026, 03:33 PMYep, I'm getting the same:
QuoteShipping not available
Your order cannot be shipped to the selected address. Review your address to ensure it's correct and try again, or select a different address.
You are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
Quote from: Chris Savage on Apr 25, 2026, 09:40 PMQuote from: granz on Apr 25, 2026, 03:33 PMYou are probably correct about it being a tariff issue. Maybe holding off for a while until other countries cut back on their tariffs on U.S. products, and then we can cut back on products from them.
There are Tindie stores I have previously purchased from that are not shipping to the U.S. currently (some are in the U.K.) because of the tariff issues.
Well, I got these 2 items.... more then wanted to pay, but no other options....
https://www.ebay.com/itm/306717973814 (https://www.ebay.com/itm/306717973814)
https://www.ebay.com/itm/177966875115 (https://www.ebay.com/itm/177966875115)
Will find one of these to replace the 5v regulator.... the one in there gets REALLY hot, so better be safe than sorry, I'd get it on there but $6.99 + like $8.xx shipping is ridiculous....
https://www.ebay.com/itm/305400148473 (https://www.ebay.com/itm/305400148473)
I seem to recall that the heat sink on my Sinclair ZX-81 was pretty big, and that it had a "spring" that transferred heat to the metal paint on the inside of the case. Maybe if you put that large of a heat sink on the voltage regulator (7805 IIRC) it will keep it cool enough.
Quote from: JKnightandKARR on Apr 26, 2026, 12:39 PMWill find one of these to replace the 5v regulator.... the one in there gets REALLY hot, so better be safe than sorry, I'd get it on there but $6.99 + like $8.xx shipping is ridiculous....https://www.ebay.com/itm/305400148473 (https://www.ebay.com/itm/305400148473)
It's so funny you mentioning the Traco TSR 1-2450. I get mine from Digikey (https://www.digikey.com/short/mb92rd0h). They're a great replacement for the LM7805, which does dissipate a
LOT of heat, since it's a linear regulator. Just be aware that the minimum input voltage is 6.5V@1A.
Quote from: granz on Apr 26, 2026, 12:53 PMI seem to recall that the heat sink on my Sinclair ZX-81 was pretty big, and that it had a "spring" that transferred heat to the metal paint on the inside of the case. Maybe if you put that large of a heat sink on the voltage regulator (7805 IIRC) it will keep it cool enough.
Maybe, IDK.... might have large enough heatsinks, even something from an old motherboard.
Quote from: Chris Savage on Apr 26, 2026, 03:30 PMQuote from: JKnightandKARR on Apr 26, 2026, 12:39 PMWill find one of these to replace the 5v regulator.... the one in there gets REALLY hot, so better be safe than sorry, I'd get it on there but $6.99 + like $8.xx shipping is ridiculous....https://www.ebay.com/itm/305400148473 (https://www.ebay.com/itm/305400148473)
It's so funny you mentioning the Traco TSR 1-2450. I get mine from Digikey (https://www.digikey.com/short/mb92rd0h). They're a great replacement for the LM7805, which does dissipate a LOT of heat, since it's a linear regulator. Just be aware that the minimum input voltage is 6.5V@1A.
Wall adapter is 9v@1A, so shouldn't be a problem... lol
Quote from: JKnightandKARR on Apr 26, 2026, 10:43 PMQuote from: granz on Apr 26, 2026, 12:53 PMI seem to recall that the heat sink on my Sinclair ZX-81 was pretty big, and that it had a "spring" that transferred heat to the metal paint on the inside of the case. Maybe if you put that large of a heat sink on the voltage regulator (7805 IIRC) it will keep it cool enough.
Maybe, IDK.... might have large enough heatsinks, even something from an old motherboard.
Again,
if I remember correctly, the heat sink on my ZX-81 was simply a flat square of aluminum - maybe 2" by 2". That should be simple enough to make, and being flat, it fit inside the case with no trouble.
Quote from: JKnightandKARR on Apr 26, 2026, 10:43 PMWall adapter is 9v@1A, so shouldn't be a problem... lol
The great thing about a switching regulator is that there's a LOT less waste in heat when your input voltage is higher. On the LM7805, as your input voltage goes up, the regulator has to dissipate more heat to regulate.
Yes, and as the original regulator is linear, using a 7V wall wart, rather than the original 9V power supply will keep the 7805 temperature much lower. Using the switching regulator replacement will keep the temp lower also.
Quote from: granz on Apr 27, 2026, 09:22 AMYes, and as the original regulator is linear, using a 7V wall wart, rather than the original 9V power supply will keep the 7805 temperature much lower. Using the switching regulator replacement will keep the temp lower also.
I bet my adj power supply would work.
Quote from: JKnightandKARR on Apr 27, 2026, 11:42 AMI bet my adj power supply would work.
Yep. Two things:
1) Make sure that you have the correct polarity. I'm not certain about the TS, but some power supply connectors from back then had the center negative, and the outer positive. Make sure that you get that right.
2) Check the datasheet for the actual 7805 regulator that is actually on the PCB. Find out what the minimum input voltage is, and make sure that you don't set the power supply below that.
Well, the composite mod is here, SMALL lil sucker!! Has 2 adj pots and a jumper to invert the colors, also have schematics, what I was thinking is, I have 2 ZX=81s, I have a 7" LCD monitor, add battery and we have a laptop... That shouldn't be hard at all.
Hah, nice. I remember back in the early '80s when I had my ZX-81, I thought about hooking up a tiny television to my system and having a "laptop." Actually, in 1986, I did take a Timex 2068 (color version of the TS-1000) and mount it inside a 50 caliber ammunition can along with a cassette tape recorder and a battery operated television that we bought from Sears. It was my own personal Commodore SX-64 "clone." I actually took my portable computer with me on a deployment to Homestead AFB (near Miami, Florida.) It was pretty cool writing programs on my portable inside our work shelter (a 6' x 8' x 10' box that fits in the back of an M-35 deuce-and-a-half)
(https://www.easternsurplus.net/Documents/Pictures/cropped-5411-00-117-2868%20S-280BG%20Electrical%20Equipment%20Shelter,%20Container,%20Tool%20Shed%20USED%20(15).JPG)
The trouble was that the "portable" computer was so heavy (probably heavier than the Kaypro, or Osborne, computers that became popular about that time) that I could feel my arm getting longer every time that I carried it. :o ::)
(https://jknightandkarr.altervista.org/Computers/parts.jpg)
I got the parts, now install n figure out the config switches...
Nice, hopefully that will get your computer up and running.
Quote from: granz on Apr 30, 2026, 06:52 AMHah, nice. I remember back in the early '80s when I had my ZX-81, I thought about hooking up a tiny television to my system and having a "laptop." Actually, in 1986, I did take a Timex 2068 (color version of the TS-1000) and mount it inside a 50 caliber ammunition can along with a cassette tape recorder and a battery operated television that we bought from Sears. It was my own personal Commodore SX-64 "clone." I actually took my portable computer with me on a deployment to Homestead AFB (near Miami, Florida.) It was pretty cool writing programs on my portable inside our work shelter (a 6' x 8' x 10' box that fits in the back of an M-35 deuce-and-a-half)
(https://www.easternsurplus.net/Documents/Pictures/cropped-5411-00-117-2868%20S-280BG%20Electrical%20Equipment%20Shelter,%20Container,%20Tool%20Shed%20USED%20(15).JPG)
The trouble was that the "portable" computer was so heavy (probably heavier than the Kaypro, or Osborne, computers that became popular about that time) that I could feel my arm getting longer every time that I carried it. :o ::)
That's cool. Atleast your console TV wasn't in danger of theft. Lol
Quote from: JKnightandKARR on Apr 30, 2026, 02:41 PMThat's cool. Atleast your console TV wasn't in danger of theft. Lol
That picture was the shelter - our telephone switching system (300 line switch) was in one, and another was converted into our mobile workshop. Our squadron was a tactical (mobile) communications unit.
My computer was just inside one of the .50 cal ammo cans. It used a truly portable television as the monitor. The TV ran off of ten C-cells, or a 120VAC cord. I never had a console TV - my parents did, but not me.
Quote from: granz on Apr 30, 2026, 02:59 PMQuote from: JKnightandKARR on Apr 30, 2026, 02:41 PMThat's cool. Atleast your console TV wasn't in danger of theft. Lol
That picture was the shelter - our telephone switching system (300 line switch) was in one, and another was converted into our mobile workshop. Our squadron was a tactical (mobile) communications unit.
My computer was just inside one of the .50 cal ammo cans. It used a truly portable television as the monitor. The TV ran off of ten C-cells, or a 120VAC cord. I never had a console TV - my parents did, but not me.
I figured. lol OK, I don't know if not having a console tv is a good thing or a bad thing... lol
Our console television was about three feet tall, about five feet left-to-right and about two feet front-to-back. If I recall correctly, it was about a twenty-five inch screen. It probably weighed over 120 Lbs, and took two adults to move it. The thing took up the entire back of our early-1970s station wagon (I.E.big car.) So, no, having a console TV is not such a good thing. Our current television has a sixty-five inch screen and (other than the awkwardness of physical size) can be lifted by a single person.
Quote from: granz on May 01, 2026, 06:14 AMOur console television was about three feet tall, about five feet left-to-right and about two feet front-to-back. If I recall correctly, it was about a twenty-five inch screen. It probably weighed over 120 Lbs, and took two adults to move it. The thing took up the entire back of our early-1970s station wagon (I.E.big car.) So, no, having a console TV is not such a good thing. Our current television has a sixty-five inch screen and (other than the awkwardness of physical size) can be lifted by a single person.
Trust me I know, had one growing up, till 1999 to be exact.
@granz @Chris Savage @MicroNut https://vdrivezx.com/wp-content/uploads/2019/12/vla81_user_manual_v1.3-1.pdf (https://vdrivezx.com/wp-content/uploads/2019/12/vla81_user_manual_v1.3-1.pdf)
Suggestions what to set SW3/SW4 to? I know SW1/SW2 outta be set to ON/OFF for the backporch signal, but kinda confused on the other 2 switches.
The manual is not very clear - it appears that you can only use this with an internal 32K RAM upgrade. But if you go to the product page (https://vdrivezx.com/vla81/) and look at the second picture (the first one showing the motherboard) it shows a Mostek 4118 1K x 8-bit RAM chip. You can see that all of switches are turned off.
I would start off with that configuration (all switches off) and see what happens. In the worst case, you only have fifteen other possibilities to try. :P You may also want to pick up a 62256 32K RAM chip and upgrade your TS-1000, per page four of the manual. That may be the best option.
Quote from: granz on May 02, 2026, 06:41 AMThe manual is not very clear - it appears that you can only use this with an internal 32K RAM upgrade. But if you go to the product page (https://vdrivezx.com/vla81/) and look at the second picture (the first one showing the motherboard) it shows a Mostek 4118 1K x 8-bit RAM chip. You can see that all of switches are turned off.
I would start off with that configuration (all switches off) and see what happens. In the worst case, you only have fifteen other possibilities to try. :P You may also want to pick up a 62256 32K RAM chip and upgrade your TS-1000, per page four of the manual. That may be the best option.
Thanks SW1/SW2 are for backporch signal mainly so only total of 4 lol
Quote from: JKnightandKARR on May 02, 2026, 01:35 PMThanks SW1/SW2 are for backporch signal mainly so only total of 4 lol
Yep, I was thinking (since all the switches are off in the photos, rather than the on & off that you discovered) that in the worst case, you would only have sixteen possibilities to try. By all means, go ahead and start off with the choice you had, and count through those four possibilities.
Quote from: granz on May 02, 2026, 06:41 AMYou may also want to pick up a 62256 32K RAM chip and upgrade your TS-1000, per page four of the manual. That may be the best option.
If you don't have a 62256 and need one, I can send you one. I have a drawer of them. Every Z80 system I ever built has one installed. It was just easy to simply split the 64K address space into 32K ROM and 32K RAM.
Yeah, and you can get quite a bit of software into 32K of ROM.
On the "office"-type Z-80 systems, the ROM could be used to copy a boot program into upper memory (RAM) and have that switch out the ROM and switch in RAM to lower memory. That is how CP/M got to use all 64K of memory in pure RAM.
Quote from: Chris Savage on May 02, 2026, 07:43 PMQuote from: granz on May 02, 2026, 06:41 AMYou may also want to pick up a 62256 32K RAM chip and upgrade your TS-1000, per page four of the manual. That may be the best option.
If you don't have a 62256 and need one, I can send you one. I have a drawer of them. Every Z80 system I ever built has one installed. It was just easy to simply split the 64K address space into 32K ROM and 32K RAM.
Sure if its not too much trouble. I'll figure out how to install later.
@granz Yeah, I got the first 2 switches are video only n maybe the mic. It's the 2nd 2 that are memory, but will take your suggestion of off/off first
New ULA is installed and I have to video setting done. As soon as I have the composite mod installed, I'll hook it up n try it.
Hope it works well.
@granz @Chris Savage Well, no signals, no image. Verified voltage at the module n I have 5V to it. Tried Gnd on module .to 5V out from the voltage reg. and got reading, since the module has 8 PTH connected to the functions, I can use them as test points. Found the pin for the input signal, and I've got a wave form similar to the manual, so the new ULA is clearly working, I've got the output pin and not getting any kinda waveform, other then what looks like noise. so probly start with adjusting the pots. Outta hook it up to my vcr, maybe the tv is the issue as well, so vcr outta help, since I already got a video from it, so far that's what I got.
I got an adapter for the TV Out for my ZX81 as well. I really had to fiddle around with the pots to get the display working. The version I got also created two large vertical black bars in the border section. I ended up using a portable 7" black and White TV circ 1980, I picked up at a Salvation Army store, which worked with the TV out instead. So you may have to fiddle around with the pots.
Quote from: MicroNut on May 06, 2026, 12:11 PMI got an adapter for the TV Out for my ZX81 as well. I really had to fiddle around with the pots to get the display working. The version I got also created two large vertical black bars in the border section. I ended up using a portable 7" black and White TV circ 1980, I picked up at a Salvation Army store, which worked with the TV out instead. So you may have to fiddle around with the pots.
Yeah, I outta find my small old lcd screen to try it on... might be my tv as well.
Quote from: JKnightandKARR on May 06, 2026, 10:01 PMQuote from: MicroNut on May 06, 2026, 12:11 PMI got an adapter for the TV Out for my ZX81 as well. I really had to fiddle around with the pots to get the display working. The version I got also created two large vertical black bars in the border section. I ended up using a portable 7" black and White TV circ 1980, I picked up at a Salvation Army store, which worked with the TV out instead. So you may have to fiddle around with the pots.
Yeah, I outta find my small old lcd screen to try it on... might be my tv as well.
@MicroNut @granz @Chris Savage (https://jknightandkarr.altervista.org/Computers/Fixed.jpg)
https://jknightandkarr.altervista.org/Computers/Fixed.jpg (https://jknightandkarr.altervista.org/Computers/Fixed.jpg)
I got it!! Lil bit o tweaking with signal input and output wires and I got a signal, and the keyboard is needing fixed.
Quote from: JKnightandKARR on May 07, 2026, 12:02 AM@MicroNut @granz @Chris Savage
...
I got it!! Lil bit o tweaking with signal input and output wires and I got a signal, and the keyboard is needing fixed.
Great! Big advance - now to get the keyboard fixed, and the 32K upgrade and you are set to go.
I got 2 replacement keyboards from Sell My Retro in the UK Keyboard (https://www.sellmyretro.com/offer/details/sinclair-zx81-~~-timex-1000--_-keyboard-membrane-replacement--_-new-63645). They are made of stronger, longer lasting material. They have the UK symbols "Rub Out" rather than "Delete" and "New Line" rather than "Enter". They are easy to replace and work well.
Quote from: JKnightandKARR on May 07, 2026, 12:02 AMI got it!! Lil bit o tweaking with signal input and output wires and I got a signal, and the keyboard is needing fixed.
Great news! It's time for some Z80 assembly work now! 8)
Quote from: granz on May 07, 2026, 06:16 AMQuote from: JKnightandKARR on May 07, 2026, 12:02 AM@MicroNut @granz @Chris Savage
...
I got it!! Lil bit o tweaking with signal input and output wires and I got a signal, and the keyboard is needing fixed.
Great! Big advance - now to get the keyboard fixed, and the 32K upgrade and you are set to go.
Yup, I'm going to try the keyboard from the other unit n see if that works.
Quote from: MicroNut on May 07, 2026, 07:28 AMI got 2 replacement keyboards from Sell My Retro in the UK Keyboard (https://www.sellmyretro.com/offer/details/sinclair-zx81-~~-timex-1000--_-keyboard-membrane-replacement--_-new-63645). They are made of stronger, longer lasting material. They have the UK symbols "Rub Out" rather than "Delete" and "New Line" rather than "Enter". They are easy to replace and work well.
Thanks. I got a one from another unit I can try first. Wish I could get one like this https://www.ginger-electronic.com/en/retro-computer/24-40-zx8-kdlx-keyboard-for-sinclair-zx81-and-zx80.html#/26-model-zx81 (https://www.ginger-electronic.com/en/retro-computer/24-40-zx8-kdlx-keyboard-for-sinclair-zx81-and-zx80.html#/26-model-zx81)
Quote from: Chris Savage on May 07, 2026, 08:30 AMQuote from: JKnightandKARR on May 07, 2026, 12:02 AMI got it!! Lil bit o tweaking with signal input and output wires and I got a signal, and the keyboard is needing fixed.
Great news! It's time for some Z80 assembly work now! 8)
As soon as my keyboard is fixed, I can try my ZX Spectrum app on my tablet, but need material to figure it out... lol
Quote from: JKnightandKARR on May 07, 2026, 09:50 AMAs soon as my keyboard is fixed, I can try my ZX Spectrum app on my tablet, but need material to figure it out... lol
Okay, PM me your address so I can send you a 62256 SRAM IC (24-pin DIP).
Quote from: MicroNut on May 07, 2026, 07:28 AMI got 2 replacement keyboards from Sell My Retro in the UK Keyboard (https://www.sellmyretro.com/offer/details/sinclair-zx81-~~-timex-1000--_-keyboard-membrane-replacement--_-new-63645). They are made of stronger, longer lasting material. They have the UK symbols "Rub Out" rather than "Delete" and "New Line" rather than "Enter". They are easy to replace and work well.
Wow! At $10 for the keyboard, and about $5 for shipping (from the USA,) this is a darned good deal for a TS-1000.
Quote from: granz on May 07, 2026, 11:48 AMQuote from: MicroNut on May 07, 2026, 07:28 AMI got 2 replacement keyboards from Sell My Retro in the UK Keyboard (https://www.sellmyretro.com/offer/details/sinclair-zx81-~~-timex-1000--_-keyboard-membrane-replacement--_-new-63645). They are made of stronger, longer lasting material. They have the UK symbols "Rub Out" rather than "Delete" and "New Line" rather than "Enter". They are easy to replace and work well.
Wow! At $10 for the keyboard, and about $5 for shipping (from the USA,) this is a darned good deal for a TS-1000.
Yaeah. Not bad at all.
QuoteThanks. I got a one from another unit I can try first. Wish I could get one like this https://www.ginger-electronic.com/en/retro-computer/24-40-zx8-kdlx-keyboard-for-sinclair-zx81-and-zx80.html#/26-model-zx81
I also have one of those. I had too much trouble trying to get the wiring in the socket. One of these days I'll try one of the ZX81's I have. I have 3 but none of the keyboards work due to age. I only have one replaced. I also have a modern kit someone made that I have put together and has those little switches on it that I play around with.
Quote from: MicroNut on May 07, 2026, 12:32 PMQuoteThanks. I got a one from another unit I can try first. Wish I could get one like this https://www.ginger-electronic.com/en/retro-computer/24-40-zx8-kdlx-keyboard-for-sinclair-zx81-and-zx80.html#/26-model-zx81
I also have one of those. I had too much trouble trying to get the wiring in the socket. One of these days I'll try one of the ZX81's I have. I have 3 but none of the keyboards work due to age. I only have one replaced. I also have a modern kit someone made that I have put together and has those little switches on it that I play around with.
I like that keyboard cause of the lil buttons, if wear out can replace
@MicroNut @granz @Chris Savage As expected, the connectors on my keyboard are damaged, I managed to swap the other top on and the system "should" be at 100% now. Getting ready to test the system. I am keeping the old keyboard, and will be using it to create a PCB to repair it using SMD buttons in the original layout using the top as an overlay, just for giggles.
EDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
Quote from: JKnightandKARR on May 10, 2026, 11:08 PM@MicroNut @granz @Chris Savage
As expected, the connectors on my keyboard are damaged, I managed to swap the other top on and the system "should" be at 100% now. Getting ready to test the system. I am keeping the old keyboard, and will be using it to create a PCB to repair it using SMD buttons in the original layout using the top as an overlay, just for giggles.
I remember that my keyboard "cable" on my ZX-81 got eaten up by my removing, and reinstalling it. I used a scissors to cut it down, and was able to insert it back into the connector with no troubles.
Quote from: JKnightandKARR on May 10, 2026, 11:08 PMEDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
Congrats! Good work.
Quote from: granz on May 11, 2026, 07:00 AMQuote from: JKnightandKARR on May 10, 2026, 11:08 PM@MicroNut @granz @Chris Savage
As expected, the connectors on my keyboard are damaged, I managed to swap the other top on and the system "should" be at 100% now. Getting ready to test the system. I am keeping the old keyboard, and will be using it to create a PCB to repair it using SMD buttons in the original layout using the top as an overlay, just for giggles.
I remember that my keyboard "cable" on my ZX-81 got eaten up by my removing, and reinstalling it. I used a scissors to cut it down, and was able to insert it back into the connector with no troubles.
Quote from: JKnightandKARR on May 10, 2026, 11:08 PMEDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
Congrats! Good work.
Too late to fix that lol
Quote from: JKnightandKARR on May 10, 2026, 11:08 PMEDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
So everything is working?!? :o Quick! Start some Z80 assembly stuff before anything else happens! :-X
Quote from: Chris Savage on May 11, 2026, 11:41 AMQuote from: JKnightandKARR on May 10, 2026, 11:08 PMEDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
So everything is working?!? :o Quick! Start some Z80 assembly stuff before anything else happens! :-X
LOL.
I remember that the ZX-81 BASIC had POKE, PEEK and USER commands. I had a subroutine that converted a string of hex characters into decimal (for the poking) and vice-versa (for the peeks.) I was able to do some Z-80 work with that.
Quote from: Chris Savage on May 11, 2026, 11:41 AMQuote from: JKnightandKARR on May 10, 2026, 11:08 PMEDIT: Keyboard swap tested and 100% FUNCTIONAL!!!
So everything is working?!? :o Quick! Start some Z80 assembly stuff before anything else happens! :-X
I've actually started reading the book that came with it. lol in the back there's a chapter where assembly starts.
Quote from: JKnightandKARR on May 11, 2026, 11:56 PMI've actually started reading the book that came with it. lol in the back there's a chapter where assembly starts.
Very cool! If you have any questions on Z80 assembly, we can start a thread for that in the appropriate forum. Since I don't have a ZX, it would be limited to the language, specifically. ;)
I used the Artic Assembler (https://www.zx81stuff.org.uk/zx81/tape/ZXAssembler) to learn Assembly on the ZX81. It resides above the Ramptop address in the ZX81.
I got an emmulator on my laptop, but no clue how to use it. Lol The book should answer any questions I have, other then language related stuff. Like 0/0 when a program is ran first 0 is for the lines remaning I think n the 2nd if there is an error, that's the line number of the error. I need to make a switch box for my composite inputs.... hooked my VCR up to coax, vcr auto off'd itself n the stupid "Smart" TV, got rid of the channel...
Quote from: Chris Savage on May 12, 2026, 07:58 AMQuote from: JKnightandKARR on May 11, 2026, 11:56 PMI've actually started reading the book that came with it. lol in the back there's a chapter where assembly starts.
Very cool! If you have any questions on Z80 assembly, we can start a thread for that in the appropriate forum. Since I don't have a ZX, it would be limited to the language, specifically. ;)
https://sourceforge.net/projects/eightyone-sinclair-emulator/files/EightyOne%20V1.41.zip/download
Hey Chris, Get this! It's an Emulator for ZX80/ZX81/Spectrum etc. Ironically it even has files for the Timex Sinclair 1000 even though its the same as the Sinclair ZX81 lol, anywho, if you hit Help menu there's a drop down option for the original keyboard for reference purposes.
Book I been reading.
file:///C:/Users/joeti/Downloads/zx81-basic-programming.pdf (file:///C:/Users/joeti/Downloads/zx81-basic-programming.pdf)
Oh and this for a 404 page is just cool. lol
https://worldofspectrum.org/ZX81BasicProgramming/
Quote from: JKnightandKARR on May 16, 2026, 10:03 PMif you hit Help menu there's a drop down option for the original keyboard for reference purposes.
Back, when I had my first ZX-81, I hooked up a real keyboard to it. If I remember correctly, I took either a photo of the ZX's keyboard, or a photocopy of my ZX, and cut out the little squares of the keys and glued them to the keys on the real keyboard. I also seem to remember that someone said to use clear fingernail polish over the paper to protect them. Because the keys are so different from those on a real keyboard, it helped having the correct ZX-81 labels on the actual keys.
Quote from: granz on May 17, 2026, 06:08 AMQuote from: JKnightandKARR on May 16, 2026, 10:03 PMif you hit Help menu there's a drop down option for the original keyboard for reference purposes.
Back, when I had my first ZX-81, I hooked up a real keyboard to it. If I remember correctly, I took either a photo of the ZX's keyboard, or a photocopy of my ZX, and cut out the little squares of the keys and glued them to the keys on the real keyboard. I also seem to remember that someone said to use clear fingernail polish over the paper to protect them. Because the keys are so different from those on a real keyboard, it helped having the correct ZX-81 labels on the actual keys.
Good idea, though I am NOT doing that to my $1,100 laptop keyboard. lol
Quote from: JKnightandKARR on May 17, 2026, 11:02 AMGood idea, though I am NOT doing that to my $1,100 laptop keyboard. lol
Hah! Yeah, not that one. Get yourself a cheapie keyboard:
$15.59 - https://www.amazon.com/Keyboard-Multimedia-Computer-Spill-Resistant-Anti-Wear/dp/B0BJDPT8V3
(https://m.media-amazon.com/images/I/71HTL5QH6fL._AC_SL1500_.jpg)
Or, even cheaper - just ask friends. You can often find people who upgrade their keyboards and are willing to give away their old ones.
Quote from: granz on May 17, 2026, 05:58 PMQuote from: JKnightandKARR on May 17, 2026, 11:02 AMGood idea, though I am NOT doing that to my $1,100 laptop keyboard. lol
Hah! Yeah, not that one. Get yourself a cheapie keyboard:
$15.59 - https://www.amazon.com/Keyboard-Multimedia-Computer-Spill-Resistant-Anti-Wear/dp/B0BJDPT8V3
(https://m.media-amazon.com/images/I/71HTL5QH6fL._AC_SL1500_.jpg)
Or, even cheaper - just ask friends. You can often find people who upgrade their keyboards and are willing to give away their old ones.
I actually have ones laying around.
Quote from: JKnightandKARR on May 17, 2026, 08:48 PMI actually have ones laying around.
Yeah, I kind of thought that you might. As I mentioned, many people have them on hand - especially people like us. ;)
I use Eighty-One alot! Very realistic. You can add video affects to the video so it can be just as fuzzy as a CRT TV. It even has the infamous ram pack bug. The Ram Pack expansion had a habit of disconnecting from the ZX81 if you bumped the ZX81 then "POOF" program gone! It is a button in Eight-One you can click to simulate it.
@JKnightandKARR how did you connect a keyboard to the ZX81? It used a 5x8 matrix of switches connected to the ULA and decoded in the rom. A normal keyboard uses a formatted bitstream via PS2 or USB.
Quote from: MicroNut on May 20, 2026, 04:22 PMhow did you connect a keyboard to the ZX81? It used a 5x8 matrix of switches connected to the ULA and decoded in the rom. A normal keyboard uses a formatted bitstream via PS2 or USB.
I was going to ask the same question...
Back when I built my keyboard for my ZX-81, I used a surplus, non-encoded keyboard. When I mentioned the glue-on key labels to Joe, I was referring to his emulator:
Quote from: JKnightandKARR on May 16, 2026, 10:03 PMIt's an Emulator for ZX80/ZX81/Spectrum etc. Ironically it even has files for the Timex Sinclair 1000 even though its the same as the Sinclair ZX81 lol, anywho, if you hit Help menu there's a drop down option for the original keyboard for reference purposes.
For a real keyboard, for a real(ish) ZX-81/TS1000 (or a separate cheapie USB keyboard for an emulated ZX,) the glue-on labels will come in real handy.
Oops :-[ I thought he was talking about a real ZX81. I did get a ZX81 simulated on a DE0-Nano FPGA that had a PS2 connection for a normal keyboard. I remember back in the early eighties picking up a keyboard from Radio Shack that you had to wire each key. I was planning on connecting it to my Timex Sinclair 1000 but never got around to it and the keyboard was eventually thrown out.
BTW ZEsarUX (https://github.com/chernandezba/zesarux/releases/tag/ZEsarUX-12.0) is another excellent ZX81/Spectrum emulator.
Quote from: MicroNut on May 21, 2026, 08:22 AMOops :-[ I thought he was talking about a real ZX81. I did get a ZX81 simulated on a DE0-Nano FPGA that had a PS2 connection for a normal keyboard. I remember back in the early eighties picking up a keyboard from Radio Shack that you had to wire each key. I was planning on connecting it to my Timex Sinclair 1000 but never got around to it and the keyboard was eventually thrown out.
BTW ZEsarUX (https://github.com/chernandezba/zesarux/releases/tag/ZEsarUX-12.0) is another excellent ZX81/Spectrum emulator.
Yeah, your FPGA ZX is the one that I was thinking about. Use a regular USB keyboard, with the Sinclair keycaps glued on, and the FPGA emulator is much better/more realistic.
Quote from: MicroNut on May 21, 2026, 08:22 AMOops :-[ I thought he was talking about a real ZX81.
Same. I get it now. :-[
Quote from: MicroNut on May 20, 2026, 04:22 PMI use Eighty-One alot! Very realistic. You can add video affects to the video so it can be just as fuzzy as a CRT TV. It even has the infamous ram pack bug. The Ram Pack expansion had a habit of disconnecting from the ZX81 if you bumped the ZX81 then "POOF" program gone! It is a button in Eight-One you can click to simulate it.
@JKnightandKARR how did you connect a keyboard to the ZX81? It used a 5x8 matrix of switches connected to the ULA and decoded in the rom. A normal keyboard uses a formatted bitstream via PS2 or USB.
My emulator is on my Acer Nitro 5 laptop, so USB easy. Lol I found it through that link you posted. Works pretty well.
Quote from: granz on May 18, 2026, 07:05 AMQuote from: JKnightandKARR on May 17, 2026, 08:48 PMI actually have ones laying around.
Yeah, I kind of thought that you might. As I mentioned, many people have them on hand - especially people like us. ;)
Only alittle. Lol
Quote from: granz on May 21, 2026, 07:43 AMBack when I built my keyboard for my ZX-81, I used a surplus, non-encoded keyboard. When I mentioned the glue-on key labels to Joe, I was referring to his emulator:
Quote from: JKnightandKARR on May 16, 2026, 10:03 PMIt's an Emulator for ZX80/ZX81/Spectrum etc. Ironically it even has files for the Timex Sinclair 1000 even though its the same as the Sinclair ZX81 lol, anywho, if you hit Help menu there's a drop down option for the original keyboard for reference purposes.
For a real keyboard, for a real(ish) ZX-81/TS1000 (or a separate cheapie USB keyboard for an emulated ZX,) the glue-on labels will come in real handy.
I wonder if I can use an adapter n plug a keyboard into me tablet for my Spectrum emu?? The on screen keyboard kinda covers it up some...
Quote from: JKnightandKARR on May 24, 2026, 04:12 PMI wonder if I can use an adapter n plug a keyboard into me tablet for my Spectrum emu?? The on screen keyboard kinda covers it up some...
Yeah, that would be an OTG (On The Go) adapter or cable. You get the kind that plugs into your tablet (micro USB-A or USB-C) and then the keyboard, or mouse or whatever, plugs into the adapter. I actually carry one of each with me everywhere - I used one this morning (Marilyn forgot her Children's Church lesson, so I was able to get it off a thumb drive.)
Quote from: granz on May 24, 2026, 05:56 PMQuote from: JKnightandKARR on May 24, 2026, 04:12 PMI wonder if I can use an adapter n plug a keyboard into me tablet for my Spectrum emu?? The on screen keyboard kinda covers it up some...
Yeah, that would be an OTG (On The Go) adapter or cable. You get the kind that plugs into your tablet (micro USB-A or USB-C) and then the keyboard, or mouse or whatever, plugs into the adapter. I actually carry one of each with me everywhere - I used one this morning (Marilyn forgot her Children's Church lesson, so I was able to get it off a thumb drive.)
I think I got one. Have to try it. I gotta bluetooth keyboard, but not much luck finding the extra keys.
If you do not have any adapters, this is the one that I used yesterday:
https://www.amazon.com/dp/B0F3X4P6GM $6.99 for 10 adapters.
(https://m.media-amazon.com/images/I/61rY8L7P18L._AC_SL1500_.jpg)
And, if you need micro-USB, there are these:
https://www.amazon.com/Togconn-Adapter-Aluminum-Keyboard-Controller/dp/B0BX9G7RDL $9.99 for 4 cables.
(https://m.media-amazon.com/images/I/71cYyXiSDkL._AC_SL1500_.jpg)
Although, I do have, and carry, adapters for the micro-, I can't find my orders for the adapters, just these small cables. The adapters are better for every-day-carry.
Quote from: granz on May 25, 2026, 08:05 AMIf you do not have any adapters, this is the one that I used yesterday:
https://www.amazon.com/dp/B0F3X4P6GM $6.99 for 10 adapters.
(https://m.media-amazon.com/images/I/61rY8L7P18L._AC_SL1500_.jpg)
And, if you need micro-USB, there are these:
https://www.amazon.com/Togconn-Adapter-Aluminum-Keyboard-Controller/dp/B0BX9G7RDL $9.99 for 4 cables.
(https://m.media-amazon.com/images/I/71cYyXiSDkL._AC_SL1500_.jpg)
Although, I do have, and carry, adapters for the micro-, I can't find my orders for the adapters, just these small cables. The adapters are better for every-day-carry.
Already got one and had my RGB keyboard working on my tablet. lol
Quote from: JKnightandKARR on May 26, 2026, 12:42 AMAlready got one and had my RGB keyboard working on my tablet. lol
Great, now, keep on keying on. ;D
I kind of figured that there was a good chance that you did have one. But they are so cheep that I just offered those links in case you didn't.
Quote from: granz on May 26, 2026, 06:27 AMQuote from: JKnightandKARR on May 26, 2026, 12:42 AMAlready got one and had my RGB keyboard working on my tablet. lol
Great, now, keep on keying on. ;D
I kind of figured that there was a good chance that you did have one. But they are so cheep that I just offered those links in case you didn't.
Though this is for a ZX Spectrum Emulator, so optional. Meanwhile, have to locate an old USB keyboard around here...
Someone has a Spectrum emulator for the PicoCalc (https://forum.clockworkpi.com/t/zx-picocalc-sinclair-zx-spectrum-emulator/20323. It doesn't run under MMBASIC, but rather is a .UF2 file that runs directly on the Pico microprocessor on the PicoCalc.
I haven't tried it yet, but it seems interesting.
Quote from: granz on May 26, 2026, 10:02 PMSomeone has a Spectrum emulator for the PicoCalc (https://forum.clockworkpi.com/t/zx-picocalc-sinclair-zx-spectrum-emulator/20323. It doesn't run under MMBASIC, but rather is a .UF2 file that runs directly on the Pico microprocessor on the PicoCalc.
I haven't tried it yet, but it seems interesting.
Interesting.