Need Help Diagnosing Mac Plus Issues

[terranceandphillip]

Hey there, Joined the forum to post this.

I have this issue when I try and start my mac plus:

https://www.reddit.com/r/VintageApple/comments/kgfhej

Does anyone here recognize the sound as a specific issue?

The computer was running fine at beginning of 2020, but stopping working recently.

I have taken the machine apart and done a visual inspection of the solder joints on the analog board and don't see any obvious issues:

https://www.reddit.com/r/VintageApple/comments/kgyihh

My best guess right now is that the capacitors need to be replaced, but have no way of confirming that. Any advice on this is appreciated. In this picture, you can notice the top of a couple of the caps looks a little 'non-flat', indicating a potential bulge...

 

[MacTech68]

I don't see any visible problem on the caps, however, these symptoms would usually indicate a bad flyback transformer.

Replacements are extremely expensive these days, so much so that buying another Mac128, 512 or Plus that at least displays a picture might be the cheapest option.

Check the color of the heatsinks on the top edge of the Analog Board. If they look blue/purple/pink/green, then I'd say that's a definite bad Flyback (not that they need to be that color for it to be a bad flyback).

 

[m1maverick]

Did you try the obvious things such as reseating all of the memory modules and connectors? If I recall correctly the system board needs to be properly connected for the system to power up.

 

[MacTech68]

Looking at one of the pics posted to reddit, I think I can see the Horizontal Output Transistor is actually cracked.

It's possible the Flyback transformer is responsible for damaging the transistor.