HP_8904A partial battery failure

[gmac34]

Hi, I have replaced the ram battery in a HP 8904A synthesiser, I have followed the instructions on the SM to keep the ram powered while replacing the battery but it seems something has gone slightly wrong. The unit booted and gave me a brief warning about some corrupted ram sectors, and that ram might be defective or battery low, I didn't manage to take a picture of it. The unit now seems to work fine, and still shows the right serial and options, the error doesn't show up on subsequent boots, did it fix itself? should I bother doing anything?
Thanks

[coppercone2]

crap I just took mine apart after reading this, looks like I got some lithode bull shit going on. Need to replace with a different cell, it might be ready to go

I looked at this a few years back and decided I would fix it and I forgot about it.

Going to put one of these bad boys in its place
https://www.digikey.com/en/products/detail/panasonic-bsg/BR-2-3AT2SPN/31750

Looks like it needs a mechanical adapter of some kind, made of silicone paste most likely.

set condition red on the ship!

[coppercone2]

and I think I had errors on that when I bought it for some reason, they went away but all functions work.


I recommend you hook it up to a scope and try the diff functions and see if there is a problem.

[gmac34]

that should be the right battery but it would be easier to get one with 3 pins like this one https://www.batteriesdirect.com/product/details/specialty-batteries/panasonic/br2-3ae2spn that should be a direct replacement, at least for the models with serial prefix 2942A and above, I'm not sure what is best to use in the early version. It's also a pain to get those in Europe because you cannot ship them by air...

I still had the original one in, marked 1991, still measuring 3.1v..  the don't make them as they use to... but how could I trust a 30 Y old battery? It did it's job

I tried a few things and all seems normal, not sure what is on the RAM apart form the serial and options, and perhaps some saved settings, the rest of the important stuff is in the ROM.
There is anyway a way to recover form a battery brownout, but I did not see any mention about a partial, recoverable? corruption.

[coppercone2]

oh no I have one that looks like a disk that is stainless steel welded. That is the newer one, but the battery voltage is correct, so I just need to make an adapter. I though that one would be easier to inteface with wires since certainly it will be glued upright with silicone and some extra wires.