Sinclair ZX80 / ZX81 / Z88 Forums

Thanks... here's the board/ula

Nice! the Zeddy sure had a huge impact on lots of us. Me and a buddy both owe our good careers today to starting off on the zeddy!

Thanks. My best friend since childhood when we had TS1000's and programmed together (Don) was down this weekend from Mi (I'm in TX), and we did the caps and transistors. I sent it back with him as he's got a ram tester and the patience to pull all the rom chips lol. I appreciate all the guidance, an...

Ok, Replaced all the caps in the power circuit and the transistor, all voltages same as originally reported. No -5, no +12. What would be next on the list? Could a ram chip problem pull mess up the voltages?

I replaced the 2 power transistors, so that wasn't it - no change in voltages.. seems like next logical thing to check/replace is the diodes in the power circuit?

Amazing...

Thanks for the tutorial too dr. beeps

Thanks, I'll order some stuff, and keep going...

following the link, transistor seems ok? (open between base and both legs) Anyway, since I'm gonna order stuff, what else might I want to order so I can get at one time? Power transistor, all the caps?....

Thanks!

Got it, thanks. Will pull the transistor in the morn and test it and go from there.

Thanks Gents, I appreciate the learning exercise. So, if I want to try and test the transistor, is that with or without power on? (sorry for the dumb questions lol) Also, any easy way to test the caps rather than just random replacement? I don't mind replacing, but want to see if the thing is going ...