Mac IIci shows red-green pixel noise from multiple video cards

[bigmessowires]

While testing different power supplies in my Mac IIci, I've suddenly run into a new problem: the video output just shows this:



The computer seems to be booting normally, judging from the chime and the pattern of HD access noises, but I only see this. I see the same pattern from the IIci built-in video as well as a Toby video card in a NuBus slot. The Toby has its own frame buffer memory, so I don't think this could be a IIci RAM problem. I can't think what might cause a pattern like this on multiple video cards.

 

[Phipli]

While testing different power supplies in my Mac IIci, I've suddenly run into a new problem: the video output just shows this:

View attachment 64680

The computer seems to be booting normally, judging from the chime and the pattern of HD access noises, but I only see this. I see the same pattern from the IIci built-in video as well as a Toby video card in a NuBus slot. The Toby has its own frame buffer memory, so I don't think this could be a IIci RAM problem. I can't think what might cause a pattern like this on multiple video cards.

Given how seperate the card and onboard video are, I'd start by asking about your ROM. Is it the stock ROM?

Have you tried another monitor?

 

[eharmon]

Might be a dumb suggestion, but did you try zapping PRAM? I managed to get a machine into a similar state recently after completely horking its PRAM configuration for the display. Both onboard video and a NuBus card just displayed garbage.

 

[bigmessowires]

It's the stock ROM. Trying another monitor is difficult since this is the IIci and I only have one monitor that will sync to it, but I did some tests with another NuBus video card and another monitor, and convinced myself that it was indeed a failure with the Dell 2001FP. But then I tried the Dell monitor with another computer and it worked OK, went back to the IIci and it still didn't work, pulled the PRAM battery and randomly permuted some NuBus cards and power supplies, and now everything is working again with the original config. Very strange.

Maybe something was loose somewhere. Or maybe my Dell 2001FP really is failing and I can expect more such strangeness in the future.

I managed to get a machine into a similar state recently after completely horking its PRAM configuration for the display. Both onboard video and a NuBus card just displayed garbage.

This could be it. It has the stock IIci video plus two NuBus video cards, and I added a third NuBus video card while trying to troubleshoot. When I removed the PRAM battery it didn't immediately help, but then after more fiddling it started working again. I've since replaced the PRAM battery, verified everything's working, shut down and unplugged the machine for five minutes, then plugged it back in and verified it's still working.