A500 RAM (trapdoor) expansion has "vanished"

[ali-b]

Ok, in getting my A500 up and running again, I've been trying a few things. the first was making fresh backups of existing (seemingly good) Workbench disks.

The target floppies seemed OK (they formatted ok) but then when attempting to copy actual data, would verify bad, seemingly randomly. After a few of these, it crashed to Guru, then after the reboot, only the 0.5Mb Chip mem was available, with the entire of the expansion RAM 'missing'

thing's checked/done:
take out and re-insert the card (several times)
inspect card for any obvious signs of badness (none and no RTC battery either as it was 3rd party card with no clock...)
re-seat any chips on the card.

next thing I intend to do is re-seat the motherboard IC's but beyond that I'm not sure what specifically to check next. I'm assuming it's only Agnus that will have any specific hold over memory issues, but I can try the CIA swap if that's likely to be a factor...

any ideas?

[TjLaZer]

Can you try the card in another A500?

[ali-b]

Unfortunately not. I only have the one, and don't know anyone nearby with another.

[ali-b]

I reseated all the socketed chips, swapped the CIA's and moved the Ram chips (on the card) to different sockets. Cleaned the connector pins in Alcohol and cleaned the keyboard membrane. (unrelated but still annoying, the number row doesn't work... ) and it's done f*** all... Guess it would be easier just to get hold of a new ram pack to test it with.

[ptyerman]

Have you tried doing the copying without the RAM expansion inserted? If it then works without the expansion, at least you know for sure it is the expansion RAM at fault.

[springycz]

I had the same problem with my A500. RAM expansion was damaged (not visibly) by a leaked battery and with RAM expansion connected Amiga didn't want to boot. When I tried it without expansion Amiga happily worked. So it might be an expansion what causes problems.

[ali-b]

the RAM doesn't even show up anymore. disk copy operations work, but with only 1 drive and 0.5 Mb require a few swaps... (and the drive write-protect sensor isn't exactly 100% accurate LOL...)
the RAM pack has no RTC or battery to leak, and it boots/works fine with or without the card installed, just doesn't register. I've bought a (supposedly) working one off evilbay, and we'll see how that goes. I'm hoping it's an ancillary logic chip on the card and not something on the motherboard.

[ali-b]

Ok replacement card arrived today and everything's sweet so I'm going to guess the old card just up and died.

[stevsurv]

You could unsolder the metal tags on the metal cover and have a look inside. The battery may have leaked and caused problems.

In the past I have removed and cleaned up a battery corroded expansion card on A500 that was dead and replaced the battery and it worked quite well!

After I cleaned it up and before fitting a new battery I tested the card in the A500 and it worked well but the time didnt work (No battery!). They are a simple design.

Ofcourse depending on severity of corrosion, the card may be able to be ressurected.

[ali-b]

It's not an A501 but a 3rd party one. No metal cover, rtc and no battery (as I said in the first post) there is no obvious sign of destruction like that. It simply stopped working...