SE/30 randomly going blank

[eharmon]

I picked up an SE/30 recently which runs fine until it intermittently totally blanks out. It's recently had the logic board recapped, then shipped with no signs of physical damage.

When it's working, it works fine, but it'll go through periods where it goes totally blank while running:

• The CRT loses sync, the gun zips around for a second on it's last sweep and then goes dark.
• Execution seems to halt, it's not just a display issue. Totally unresponsive.
• Toggling power on the system yields the same result. The CRT powers up but gets no sync.
• The hard drive keeps spinning (and spins up after power toggle), so some of the power rails are definitely still live. The cooling fan spins as well.
• A buzzing (not loud, not high-pitched) sound seems to come from somewhere, but I can't quite place it. Doesn't sound like mains or a basic short. Might just be the fan rattling but I think it's not always present.
• After waiting a bit and toggling power, the machine starts working again.

Given the drive is spinning and there's no boot chime, it feels safe to rule out the usual analog board signal generation problems.

Further, given the problem is intermittent, it feels like it could be a heat expansion issue with broken solder joints. Before I start digging across the board and end up reflowing everything, anyone have an idea where to look given the symptoms?

(I should note, I did replace the memory and drop a ROMinator in it, but the symptoms don't seem related to those changes...unless the ROM is warping out of the socket as it heats? Seems like it would manifest in a different crash in that case).

 

[Johnnya101]

While waiting for someone else to reply, you can check the solder joints for the connectors on the analog board. Forget the names/numbers, might be the yoke connector or something? Could be cracked joint. When cold, the joint is good, when hot, it pushes outward and loses connection.

You can also check this by slapping the side while it has a blank screen. The image should come back.

 

[volvo242gt]

Power it up without the bucket. See if you can recreate the issue by wiggling the AB to LB harness along its length. I have some similar random issues with my SE that are related to the cable harness itself.

-J

 

[unity]

Not just the analog board, but they love to crack at the mobo too. Handy diagram to get the most common issues.

 

[eharmon]

Futzing around seems to have made it worse, but maybe in a good way -- I can basically never boot at all now, sometimes it'll give me a checkerboard screen, sometimes totally black, and sometimes the CRT will sync for just a fraction of a second with the checkerboard visible before it blanks out.

I now suspect all these cases might be the same trigger, which seems very similar to this: https://ronangaillard.github.io/posts/my-mac-se30-is-back-alive/

There's a slight warp in the corner of the board towards the memory slots, which makes me wonder if I've also got address line problems. I guess I'll tone all those out and see where I get.

 

[bcschmidt]

Has the machine been totally recapped? And did you have the logic board out to inspect for battery damage?

 

[eharmon]

Since I hate leaving things hanging in case someone else comes looking:

Yeah, totally recapped and the caps seem fine. No battery damage, no obviously blown caps anywhere. I feel pretty strongly about a cracked trace along the address lines or a damaged memory socket, due to the warped board.

For now I've shelved it to come back to later, I'll update the thread after I tone out all the traces.