Timex Sinclair 1000 repair

[JKnightandKARR]

https://jknightandkarr.altervista.org/Computers/PowerSupply.jpg
Power Supply at the jack.


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_B.jpg
Couple of shots of the 9V at the card edge connector. Kinda messy..


https://jknightandkarr.altervista.org/Computers/M1.jpg
M1 at the card edge connector. Freq = 810 Khz.


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_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
Temp at the voltage regulator


https://jknightandkarr.altervista.org/Computers/Z80.jpg
Z80 Temp

[Chris Savage]

Well, I mean your 5V, Φ and /M1 signals look good. So it would seem the Z80 is running.

[JKnightandKARR]

Well, 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.

[Chris Savage]

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.

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.

[JKnightandKARR]

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.

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.

[Chris Savage]

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.

I have three types of probes for my multimeters (not counting temp, current, etc).



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".



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.



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.

[JKnightandKARR]

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.

I have three types of probes for my multimeters (not counting temp, current, etc).



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".



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.



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
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.

[Chris Savage]

I'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?

[JKnightandKARR]

I'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.

[Chris Savage]

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.

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.

[granz]

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.

[Chris Savage]

Also, related to this: Brian (AKA @MicroNut) has (had?) a ZX-81 remake.

Define: remake?

[JKnightandKARR]

Also, 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.

[Chris Savage]

i'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, I've posted about these before, but didn't think it was an exact replacement, but rather a clone using some updated parts.



I was going to order one of these last year, but the the tariff thing ruined that.

[JKnightandKARR]

i'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, I've posted about these before, but didn't think it was an exact replacement, but rather a clone using some updated parts.



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