Sinclair ZX80 / ZX81 / Z88 Forums

I gave bbc een trying to replace the caps on my 48k spec issue 3b. Problem when powering up i get red lines then restart then copywrite notice and repeat. Finally eirther stops black screen or a few colour squares.

Any advice appreciated

Thanks!

Do you have a multi-meter? If so use the continuity checker to see if the tracks are actually broken. If not then get one. They are cheap and extremely useful!

Did it work ok before changing the caps?

Did you change all of the caps in one go or did you do a couple and then test, and repeat until all are done? I.e. do you know changing which caps caused the issue? If so then look for damage / unwanted solder in that area.

Obvious one but have you fitted them all using the correct polarity? Its easy enough to put one in the wrong way round. I know this from experience.

Rule #1 of modding: check that machine works before modifying anything.
Rule #2 of modding: if after that you find machine doesn't work anymore, it will be because of whatever was modified just now. Double-check, triple-check, or undo if necessary.

Sure there's ESD, pcb tracks where a crack develops while you're working on the board, etc. But in practice, I have yet to encounter a case where the above doesn't hold. Don't modify a machine which you don't know whether it works. Unless it helps to make a repair easier (composite video mod comes to mind).