General Category > Lisa Troubleshooting and Repair

Apple Lisa 2 I/O board problem - garbage on the screen

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sigma7:
Since this is a 1/5 or 2/5 I/O Board, then I suppose it used to have NiCd batteries. If so, there is a good chance they leaked and the board has or had corrosion damage, and then probably some repairs.

So I wonder, does this board have any jumper wires that were installed to repair corrosion damage?

If so, perhaps one is misconnected. Hence this suggestion:

Check the bad board for any jumper wires that do not exist on the good board, and for each of those: check continuity on the good board between the same two points where the jumper wire is connected on the bad board. You may find that there is a jumper connected between two points that should not be connected.

greniu:
yes, the board (from Lisa 2/5) had corrosion earlier due to battery leakage but I checked that it only has one jumper wire, which is connected correctly. I also measured the continuity on the pins on the card edge and did not notice anything suspicious. The big mystery to me is its behavior.

greniu:
hi,

I repaired the board. The fault was in the IC U10D(LS09). Pin 3(/VPA) had static 0 value, but should have 1 (and small activity at the power on). Thank you for your help and tips.

sigma7:

--- Quote from: greniu on April 13, 2025, 01:56:32 pm ---I repaired the board

--- End quote ---

That's wonderful news, congratulations, and good work!

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