Apple Lisa I/O board diodes

Adrian Graham witchy at
Sat Feb 20 13:10:21 CST 2016


Removed and cleaned up the components around the area, cleaned up the holes,
resoldered everything and replaced the 2 10K resistors that perished, check
for continuity, spend an hour trying to find a US power cord and...

Same can't be said for its ProFile however, it span up and came online for
around a second before gracefully powering down so obviously a PSU issue
there. Add that to the 'things to fix' list.

Turns out my other Lisa is an upgraded 2/5 as well, I thought it was a
native 2/10 so the I/O board is the same as the damaged one. For reference
D8 is a 1N5234A 6.2V 20mA Zener. That machine doesn't power up either but
I've never tried in the 10+ years I've had it.


On 19/02/2016 01:02, "drlegendre ." <drlegendre at> wrote:

> FYI, I get a 403 on that link.
> As for the diode, unless the leads are seriously rotted, why not just make
> a +note+ of it - and leave it alone? It's a hermetically sealed package
> (glass+metal, right?) and not likely to have suffered in any way, aside
> from the cosmetic issue.
> On Thu, Feb 18, 2016 at 6:51 PM, Adrian Graham <witchy at
>> wrote:
>> 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
>> Cheers!
>> --
>> Adrian/Witchy
>> Binary Dinosaurs creator/curator
>> - the UK's biggest private home computer
>> collection?

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

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