Old Macintosh monitor shows doubles?

[maldata]

Hi all,

I'm having trouble verbalizing what's happening on screen, so I'll post a picture instead: https://imgur.com/a/prN5nk4

The screen kind of has bands where things are duplicated... you can see the cursor has a nearby clone, and the bar at the top is all messed up, and the icons on the right as well.

This is a Macintosh SE/30 from 1988. It still boots up, and it seems to still work just fine. As far as I can tell, the monitor is the only problem. I'd like to fix it, but since I can't define the problem, I can't google for a solution. I'm also having trouble finding any information about the monitor hardware itself. Seems like a safe bet that it's a CRT, but that's about all I can say.

If you have any ideas about what the problem might be, or even what I should search for, I'd love some help. Thanks!

[stj]

Re: Old Macintosh monitor shows doubles?

if it's jumping around then it's the monitoor vsync circuit,
if it's stable then i suspect the motherboard has a fault in the vram addressing.

do you know the refresh rate of the signal on that mac? 25KHz??

[maldata]

Re: Old Macintosh monitor shows doubles?

if it's jumping around then it's the monitoor vsync circuit,
if it's stable then i suspect the motherboard has a fault in the vram addressing.

It's stable, there's no jitter in it at all.

do you know the refresh rate of the signal on that mac? 25KHz??

Nope. I don't really know anything about it, I haven't opened it up yet. Do you think this would be documented somewhere? If not, is there another way to find out?

Thanks!