IIcx troubleshooting

[Gil]

This god damn machine is driving me crazy. I got my refurbished PSU back from Uniserver recently. Back in 2013 he also recapped the logic board. No dice. Machine only stays powered on when power button is "locked" or keyboard power is held down. No chime, no video, no hard drive spin up. Green power light is on. Tried booting with/without Nubus video, with/without drives installed, with/without PRAM battery, etc....same thing. Any ideas? This thing is causing me to drink.

 

[techknight]

Failed IC, or rotten traces on the logic board. That would be the only thing that would cause this, Outside of bad ROM or something along those lines. 

 

[Juror22]

When I had booting issues (known good PSU - it worked with other boards) my method was to follow the startup circuit from the schematics and look for issues there. To do that, I took the MB out of the case and hooked everything up on my bench so that I could get at it and take measurements, check for continuity on traces, etc.

If you go this route, be careful with ESD precautions.  In the end, I got another MB and re-capped that one before it leaked allover.  I never did sort out the original issue with mine, but maybe you can with yours, since it is in better shape than mine was.

 

[Gil]

Looks like I'll have to get a replacement logic board then. Gah.

 

[trag]

Well, don't dispose of the old board. The power-on circuitry is in one locale and pretty well understood and the schematic is available, so it's definitely fixable by a probe and solder kind of person.

 

[Gil]

Well, don't dispose of the old board. The power-on circuitry is in one locale and pretty well understood and the schematic is available, so it's definitely fixable by a probe and solder kind of person.

Definitely not my area of expertise. I don't know a thing about soldering. I'll keep the board, though.

 

[LazarusNine]

Definitely not my area of expertise. I don't know a thing about soldering. I'll keep the board, though.

This forum is where I first explored and later succeeded in soldering capacitors (etc) on a motherboard. All the info is here (and YouTube) if you ever want to learn.