Apple Lisa I/O board diodes

Adrian Graham witchy at
Thu Feb 18 18:51:57 CST 2016

Hi folks,

'Decaying battery' panic led me to unearthing my Lisa 2/5 to check the state
of the batteries on the I/O board since it hadn't been out of its box or
powered up since 2005. Fortunately the damage is very minimal and is only
restricted to track discolouration and external rotting of one particular
diode which I can't find mention of on my schematics.

Anyone with a 2/5 care to check their I/O board for me please? The diode is
D8, just above the battery location. It's in the board in such a way as to
make its markings pretty unreadable in the pictures I took before cleaning,
but it's the only white diode in the machine and I'm guessing it might be a
5.6V 1N4734A based on what I can see. Fortunately it still works for now,
0.7V voltage drop.

Pic of the board before cleaning is at


Binary Dinosaurs creator/curator - the UK's biggest private home computer

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