| Attachment | Size |
|---|---|
 Mac Plus with vertical broken lines in display | 296.36 KB |
| Mac SE/30 with alternating black and white horizontal lines | 237.19 KB |
I have a couple of old Macs that I'm working on - a Mac Plus and a Mac SE/30.
The Mac Plus started with a bong, but had no display. The SE/30 displays alternating black and white horizontal lines.
I tore both down and did a basic cleaning, hit the jumpers / headers with contact cleaner and reseated socketed chips. There was no change in the SE/30, but the Mac Plus now has a display, albeit with multiple broken vertical lines.
I still have a lot to do. I plan on reflowing solder joints on the headers and recapping the analog and motherboards. Given that the SE/30 has those nasty little failure-prone surface-mount can capacitors, I suspect it's issue lies there (I see no evidence of leaking caps on it yet, though).
In any case, I just thought I'd post here to see if there's anyone who knows if these problems are attributable to something more specific, like a bad memory chip, rather than more general issues like solder joints and/or failed caps.
This is textbook Simasimac (also see here). It is usually caused by the surface mount electrolytics leaking (as you suspected). The leakage is between the components and the PCB, so it is not necessarily visible prior to rework.
The solution is capacitor replacement and thorough board cleaning, preferably ultrasonic.