Apple IIc seems dead... any way to diagnose? Fixes to try?

[spacecadet]

I have an Apple IIc that is actually the first computer I ever owned back in 1984, so I have a sentimental attachment to it and don't want to replace it wholesale. (Kinda already did with my IIgs anyway, but I still get drawn in by my IIc occasionally, because it's my first.) I want to fix it.

 

Last time I fired it up, the floppy drive no longer seemed to work but the computer itself did. This time, though, I'm getting nothing. No beep, blank screen. The power light does come on and if I plug the monitor in *after* turning on power, I get gibberish on screen. I also get a couple lines of gibberish if I command-reset and hold it, but then a blank screen again when I release.

 

I opened it up, tried reseating whatever I could, checked for blown or leaky caps etc. Didn't really see anything except one of the big caps behind the power supply looks a little weird, but it's enclosed in some kind of heat shrink tubing so I think it's just the sheath that's making it look strange.

 

I know the RAM can go bad (I searched the forum) but people with that problem seem to get *something* on screen, and a beep.

 

Is this total non-functionality a common thing that happens? If not, where would you start trying to figure out the problem?

[Keatah]

What does the gibberish screen look like? And the first thing with troubleshooting is to check for good power and good clock

[spacecadet]

What does the gibberish screen look like? And the first thing with troubleshooting is to check for good power and good clock

 

Yeah, I figured I probably should check power, but I'm always a little afraid of doing that (want to avoid electrocuting myself). Guess I'd better figure out what precautions to take and do it, though.

 

How do I check clock? I found one other site that said this but I don't really know what I'm supposed to do.

 

I do have a decent multimeter and an oscilloscope.

Edited December 14, 2016 by spacecadet