Have any of you seen this symptom before, and if so, what culprits would you suspect?
https://www.youtube.com/watch?v=6G_XFwAmVrc&feature=youtu.be
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Is it just a video issue? That is, does it beep (is that "squeak" heard on the video coming from the speaker?), does CTRL-G work, disks boot, etc?
Those are all very valid questions. I will check on each procedurally, tomorrow.
I was trying to determine why a Rev 4 board had an issue, so I swapped all of the video logic from a ][+ Rev D board to it, it didn't change anything, then when I fired up the Rev D with the chips from the Rev 4, it gave a blank screen, so I swapped every chip back, and it lit up like that. I have seen a lot of video isses and RAM issues and can usually diagnose them at a glance, but this one is new. I have never seen that kind of pattern before, at all, ever.
If it was just a line at the top I would suspect VSYNC, but, this is in WTF land in my assorted experience.
When I was swapping the parts back, I noticed that the Rev 4 had two incorrect chips in its set, as I went by chip ID, but I did not look close enough at two of them when doing the first sqap to notice that they were off by one number. Apparently, the previous owner thought that a few chips could be substituted that I know cannot, so I suspect that something was shorted in the process, but that was a lot of parts that could be affected that I would need to probe. (The CPU was also inserted backwards on arrival, so nothing about that Rev 4 board in any way shocks me, and I am pretty sure that its xtal is damaged, especially given that when it arrived it was n/c. )
I will put a speaker on both boards and check for beeps. I tend to check for video first, but the startup beep is ealier in the init process, and I should have checked that.
Beep works, boots to DOS 3.3 in slot 7. Once this occurs, I have an almost black screen with occasional lines or dots of light dancing around. Somethind is absolutely off with video sync, or video signal encoding, but that is as far as I managed to get thus far. I restored two other boards this week, and I verified that the Xtal on the Rev 4 is dead, so I absolutely do need one of those.
Somewhere I have a donor //e board that should have a good Xtal, but although I found the case pieces and the kb mech, I do not know where I put the mainboard. I know where it should be, but of course, that is never where things are when you need them.