macintosh analogue board reconditioning

From: Chris <>
Date: Wed Oct 24 22:42:48 2001

>I just in the last few minutes switched the machine on to photograph the
>display for your expert appraisals, and found that its behaviour has
>changed since it has sat. Now when I switch it on the internal speaker
>makes a repeated popping. I'm guessing the power supply is resetting
>itself continuously for whatever unknown reason.

In the pre SE analog boards (128, 512, 512ke, Plus... they all used
essentially the same board), there were a few common problems.

One was a cracked solder joint on the main power feed (?). I think its
location was "J1", if I remember correctly. The joint looked broken, in
that the pin sticking thru the back side would have a blob of solder
around it that would have a crack in it, and possibly be seperated from
the board. If I remember right, it was a red cable in a group of cables,
located kind of in the center of the board.

Another common problem was a bad high freq capacitor. It was a large
capacitor located near the top of the analog board. I think it might have
been the only large cap up there. Unfortuantly, it didn't tend to show
any damage to a visual inspection. I can get specs on the cap and
location when I am at work tomorrow.

The final common problem was a bad diode near the bottom of the board.
When it was bad, the machine would make a "flup flup flup" kind of noise
when you try to turn it on (Ah HAH... sounds like what you might have).
Again, it showed no signs of damage toa visual inspection, but would test
bad. And again, I can get specs on it when I get to work tomorrow.

An ever so handy book for fixing these problems is "The Dead Mac
Scrolls", but good luck finding a copy, I think it has been out of print
for some time (although, there may be an updated version, I just tend to
doubt it will cover the old units). I happen to have a copy, and would be
more than happy to skim thru it and work with you to find the problems
and repair them.

I will email again tomorrow with better details of where to check and
what to test.


Received on Wed Oct 24 2001 - 22:42:48 BST

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