Wednesday, November 30, 2016

Another A500+ Motherboard - Part 1

So on the Amiga Facebook pages, a rather nice chap (hi Russell!) let me have an A500+ motherboard for pennies. This board, as per the majority of A500+ boards, has battery leak damage.

Green edge connector

This does not look good

Curse you Varta!

So, anyway. A quick power up and all I get is, rather unsurprisingly, a black screen. This would normally mean a CPU failure but given the extent of the battery damage, this is a bit meaningless.

First things first, I removed all the removable chips to check for damage to the sockets. Again, as is fairly typical with these things, the Gary socket was toast. A connector in the socket had already disintegrated due to the corrosion from the battery leak and Gary himself was looking a little worse for wear.

Alas, poor socket...
This will need replacing. The picture doesn't really show how green the contacts are across the whole socket.

On to Paula. Oh, dear. The bottom half of her socket is almost as bad as Gary but the top looks OK. This will still need replacing though.,.

Even Agnus did not escape unscathed. There were telltale signs of green on her 84 pins too which did not surprise me (no picture I'm afraid) so, as I precaution, I will replace her socket as well.

The other chips faired rather better. The two CIAs, Denise, the ROM and CPU were all unscathed so no socket replacements needed for these. It looks like I will need to replace at least one, possibly more of the logic chips that are in the are of the acursed battery. The chip U12, which is a 74LS244, took the brunt of the leakage. Fortunately, I have one of these in my box of bits. I don't have any others though, so I'm hoping everything else can get away with a bloody good clean.

First task, remove the Gary socket. Normally, I would just cut the old socket off and then de-solder the pins but, for some reason, I decided to be a bit more careful and I'm glad I did. Once I had the socket off I could check for any further damage (there was a little bit) and try to clean any other corrosion up.

Gary socket gone - some cleanup works carried out.
It was at this point I realised I had no sockets of the same size as Gary's (or Paula's). I did have some smaller sockets with the same style of pins so I hatched a cunning plan. I would clean up the plastic frame from the original socket and remove the pins from the small socket and place them in the big socket. This was a lot less fun than it sounded.

Half Completed Gary
Once I had replaced all of the pins I realised that I would have to do the same again for Paula. But that's for next time...

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