Quoting Nigel Williams <nigel.d.williams at gmail.com>
As no one jumped in regarding my query, I thought I would venture out
along and try the tapping-along-the-seam technique previously
described and see if I could break into the dead Apple //c power
brick.
The tapping technique worked very nicely, although I had to apply
leverage with a screwdriver hammered into the seam to really crack the
two halves apart.
The scene of desolation inside revealed why it is dead-dead-dead, see
pictures here:
https://picasaweb.google.com/118247290269860741639/AppleCPowerSupplyBrickFa…
The smell is interesting too, it was nicely bottled up inside the
sealed PSU until I opened it...
looks like all 4 diodes are blown in half or burned in half from what
i could see.
Now that I've maanged to view the pictures, my comments...
It's clearly a linear suppl. The 4 diodes and capacitor provide a DC
output (unregualted). Is that the only output, or are there AC outputs too?
What I do do first is desodler the transformer secondary connections from
the PCB and put the PCB aside. Check the continuity of the primary
winding (between the live and neutral pins of the mains input plug) and
the secondary (or -ies). If any are open, the transformer needs a rewind.
Actually, if the primary is open, there may be a thermal fuse inside the
trnasofmer that has failed, protectign the rest of it. You might be able
to find and replace that without rewiding the whole thing.
If you have a 'megger', do an insualtion test on the transfomer --
between each widing and the core and betwee the primaray and each
secodnary winding.
Then, with The PCB still removed, connect mains with a ligbt bulb
(low-ish wattage) in series. It must be a real filament bulb, of course.
The blub should remain dark. If it glows, you'ge got shorted turns,
probably due to burnt insulation. again rewind time...
If the transofmer is OK, then it's probably worth replacing the 4 diodes
and the capacitor (the latter may be OK, but I woudn't trust it! That
should get it going again.
-tony