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SE/30 Motherboard D1 and D2 (near clock battery) - what are they can ideas to repair?


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Hi

 

I've got a SE/30 and the clock battery had started to do it's worst. I have got the lion's share off and I believe most of the chips can be cleaned and resoldered.

 

However there are two tiny rectangular blocks, each with 3 pins - perhaps transistors. One is completely gone destroyed, but the pads are good. The other is connected but in bad shape. 

 

Does anyone know what D1 and D2 are, what they do and any ideas to replace them?

 

Many Thanks

 

Alex

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Edited by solidpro
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I also just noticed that chip UJ4 is missing one pin - eaten away completely by battery acid.... I guess i'll find out if that pin is used when I realise the board is a write-off but if anyone has dealt with a missing pin on UJ4 before, i'd appreciate any experiences. There doesn't look to be anything left it of it try and reconnect...

 

cheers

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Hello,

 

It sounds like there might be quite a lot of battery damage on this board. Are you able to provide some high resolution photos of the entire logic board? These photos would help everyone here in terms of evaluating whether or not this logic board is too far gone to repair.

 

These small rectangular parts are readily available SMD 1N914 diodes. They prevent a clock battery that is installed backwards from frying the logic board. If you are just trying to get this computer working again, the clock battery circuit is not strictly necessary, and so you could focus on it later. I would recommend getting the computer into a state where it can boot into the operating system before replacing these parts, as fixing this circuit won't resurrect an otherwise dead computer.

 

UJ4 is a 74F258 RAM MUX chip. Luckily, this part is still easily available, and it could also be replaced.

 

The biggest unknown  is whether or not more components than these are damaged. Not every part can be replaced, and many are proprietary. Circuit traces are also likely broken throughout this board, and they would need to be identified and patched as well. From your description and photos, I would predict that both of these problems exist, unfortunately. This is definitely not to say that it is impossible to repair such a computer, but it might present some difficult challenges.

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