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Diagnosing Macintosh Classic II not booting

pascalw

Member
I recently got my first Classic II. The case is in great condition but unfortunately it has a few issues that I'm now trying to diagnose.

When I turn it on I can hear the hard drive, fan and processor running. However the screen remains black. When I let it run for a while and turn it off and on again, the screen starts working again but output is completely scrambled (see attached photo). From what I've read this would indicate bad capacitors on the analog board, is that right? I also noticed a quite suspicious looking capacitor (gray, 0030 all the way at the bottom on the picture) on the analog board, see here. Is this normal?

signal-2022-02-04-202858_001.jpeg

The logic board itself appears to be in very good shape. The battery hasn't leaked and I couldn't find any traces of leaking capacitors either. I did notice some differences in how the ROM chips sit on the board, see below:

signal-2022-02-04-213349.jpeg

The two left-most chips have a bit of space between the chips and the board. Could this be an issue? I removed the second chip from the left and re-seated it, but it doesn't seem to get any closer to the board than this.

The logic board itself appears to be in really good shape:
signal-2022-01-28-200456.jpeg

Any insights would be greatly appreciated :)
 

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joshc

Well-known member
Recap the logic board first, then the analog board and go from there. You can read voltages from the floppy port.

The 'grey capacitor' you photographed on your analog board is not a capacitor so that doesn't need replacing and what it looks like is normal.
 

LaPorta

Well-known member
As Josh said, that funky looking thing (whatever it is) always seems to have a rubber boot and sit at an angle. That is normal. Definitely what everyone else said.
 

3lectr1cPPC

Well-known member
I agree with the above, I just wanted to add a couple things.

You can tell that the logic board caps leaked because the dust around the caps has soaked up the leaked fluid - you can see this in the photos you've uploaded. If you're skilled enough at soldering, you may also want to remove chips like U6 as the fluid has likely gotten under them as well. An ultrasonic cleaner can also work to get under the chips on the off chance that you have access to one.

You're pretty lucky by the looks of it - I see plenty of capacitor fluid but no corrosion yet. It looks like they've only leaked recently, meaning they haven't had time to damage anything yet. The computer likely isn't booting right now because the fluid is causing all kinds of shorts. Cleaning it off may result in the computer working, but you'll want to get them replaced before they can leak more, plus, sound at the very least won't work without them.

Your initial startup issues are likely due to bad analog board capacitors, it's another known issue on the Classic boards. Get both recapped and cleaned really well and you'll probably have a working Mac!
 

pascalw

Member
Thanks for all your responses, very insightful! I've been reading about recapping. I'm not experienced with this stuff at all, but it's a nice challenge :) Indeed it seems I'm fortunate there's no corrosion on the logic board.

I'm still wondering about some of the ROM chips not sitting flat to the board (see photo 2 above), is this a problem? Since the pins are pretty long I expect it should still be able to make decent contact?
 
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