Mac has EVERY issue? Driving me crazy...

[OneRandomUser22]

Ok, so this is a doozy. My Mac 512k has been sitting in for a few months, and now I go to turn it on to discover it has a MYRIAD of issues going on. I don't even know where to start. Could one issue be causing another? Looking for advice.
Everything going on:
Both 400k drives (internal and external) are not working. They have power, but don't attempt to read any disk I put into them. The external drive whirs for a few seconds when it powers up, then shuts off and doesn't do anything. When I insert a disk, I get the Mac with an X on it onscreen, and the drive makes a faint pulsing noise, as if it is trying to spin the disk but doesn't have the force.
The internal drive does even less, no movement or noises at all. Both drives are cleaned and lubricated.

Next, about 1/2 of the time when I power the Mac, it will have some kind of issue. Sometimes, it has a checkerboard pattern. Sometimes it's a simasimac screen. Sometimes, the screen remains dark, and the Mac beeps over and over at random lengths.

The only thing I'm leaning toward is that it's some kind of power issue. Could too little power going to the logic board explain all the symptoms above? And if so, what should I look at?

Thanks in advance for any help!

 

[jasonfortheworld]

Number one guess for the intermittent issues might be related to the caps if they haven't been replaced yet. I brought my 512k back from the dead by just replacing all the caps on the logic board and analog board.

Regardless, it sounds like a power issue anyway. If caps aren't the problem then something else on the analog board is likely to blame.

As for the floppy drives, it's also possible their caps have trouble too, but I'm not very familiar with those drives myself and even if they have caps on them like the 800k and 1.4 drives.

 

[OneRandomUser22]

Number one guess for the intermittent issues might be related to the caps if they haven't been replaced yet. I brought my 512k back from the dead by just replacing all the caps on the logic board and analog board.

Regardless, it sounds like a power issue anyway. If caps aren't the problem then something else on the analog board is likely to blame.

As for the floppy drives, it's also possible their caps have trouble too, but I'm not very familiar with those drives myself and even if they have caps on them like the 800k and 1.4 drives.

Ok, so as I type this I have just found the culprit. I tried jiggling the cable that connects the analog board to the logic board (on the analog board side) and that has brought the disk drives back to life for now.

Obviously, that’s not really a fix. I assume at least reflowing that connector would be a good idea?

 

[jasonfortheworld]

Yeah I would double check all the major joints and reflow them. Glad it's a pretty simple fix!

 

[OneRandomUser22]

Yeah I would double check all the major joints and reflow them. Glad it's a pretty simple fix!

And right after I post this too…

I have this crazy luck where I can spend hours trying to fix something with no success, then five minutes after I make a forum post I find the problem

It’s happened at least 3 times before.

 

[joshc]

Yup, that's a common failure point on pre-SE compact Macs.

 

[ESM-NL]

Both 400k drives (internal and external) are not working. They have power, but don't attempt to read any disk I put into them. The external drive whirs for a few seconds when it powers up, then shuts off and doesn't do anything. When I insert a disk, I get the Mac with an X on it onscreen, and the drive makes a faint pulsing noise, as if it is trying to spin the disk but doesn't have the force.
The internal drive does even less, no movement or noises at all. Both drives are cleaned and lubricated.

This sounds like a voltage problem to me. Have you measured the voltages with a multimeter? Here a photo on how to measure.