Timex Sinclair 1000 repair

[JKnightandKARR]

Ok, 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..

[JKnightandKARR]

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/ since from my searching, the originals are prone to failure, so that's what I have so far.

[Chris Savage]

So it appears that the issue is either in the video output, or the video input of your display.

[granz]

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.)

[JKnightandKARR]

So 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.

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.)

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.

[granz]

Can'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.

[JKnightandKARR]

Can'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.