exxos's Atari, Amiga & retro forum

rubber_jonnie wrote: 31 Jan 2025 09:34 I've not decided yet,

You should plan to get the 1MB of chipmem running(0.5mb trapdoor/solder on mb)
If you want to add some extra ram the upgrade through the CPU socket is better because this will be fastram, and it will speed up the machine a little bit.
With that config you can play all the standard a500 games.

Strange that the memory expansion does not work, I would first try to test another memory expansion.
The a500 memory expansion connector seldom breaks.
If the memory expansion has had some corrosion my guess would be that this is the issue and that one of the chips is dead.

It is hard to see, but is that some damage on the underside of the mainboard near the expansion connector?
How did that happen?

Diagrom can also be a great help in diagnosing these kind of issues.

Maximilian wrote: 31 Jan 2025 11:18
You should plan to get the 1MB of chipmem running(0.5mb trapdoor/solder on mb)
If you want to add some extra ram the upgrade through the CPU socket is better because this will be fastram, and it will speed up the machine a little bit.
With that config you can play all the standard a500 games.

So I did a bit of probing and it looks like A2 and A5 have really off signals, which is suggestive of a bad connection somewhere, so I'll look into that.
CAS/RAS look absolutely fine too.

Maximilian wrote: 31 Jan 2025 11:18 Strange that the memory expansion does not work, I would first try to test another memory expansion.
The a500 memory expansion connector seldom breaks.
If the memory expansion has had some corrosion my guess would be that this is the issue and that one of the chips is dead.

Well, there is evidenence of a battery leak, the pins were green, plus the solder on the PCB looks very dull, so I think the problem may be there.

Maximilian wrote: 31 Jan 2025 11:18 It is hard to see, but is that some damage on the underside of the mainboard near the expansion connector?
How did that happen?

I don't see any damage, though the solder in places is very dull.

Maximilian wrote: 31 Jan 2025 11:18 Diagrom can also be a great help in diagnosing these kind of issues.

Yes, if I can't get it to work I will try that, but I think I need to deal with the solder joints on the expansion slot first.

OK the expansion connector is off and having a hot ultrasonic bath.

The board looks undamaged but needs to be cleaned up before I reinstall the connector.


More later.

I'm trying to remember if I got a memory upgrade shipped with this A500 (but not fitted to it) or if that was another one...

I do have a memory upgrade with signs of a leaky Varta having been installed in the past but I'm pretty sure it wasn't present inside any of my A500s.

I'd better check the other ones as soon as I can.

Hoping it all works after the clean up @rubber_jonnie

OK so this looks a lot better:


Trouble is, though it looks great, it made no difference once the pin header was soldered back in and the RAM board is supposedly tested and working by the seller...

JezC wrote: 31 Jan 2025 13:14 I'm trying to remember if I got a memory upgrade shipped with this A500 (but not fitted to it) or if that was another one...

I do have a memory upgrade with signs of a leaky Varta having been installed in the past but I'm pretty sure it wasn't present inside any of my A500s.

I'd better check the other ones as soon as I can.

Hoping it all works after the clean up @rubber_jonnie

I'd definitely be checking just in case. Sadly the clean up didn't resolve the issue, but I'll crack on and see what I can find.

OK, so A2 and A5 are still very off, so I need to trace them out on the schematic.

If you have a PLCC extraction tool then it could be worth it to extract, inspect and clean the Agnus and the socket.
And check Gary.

You were very unlucky to have corrosion on that connector, I repaired many of these machines and I only replaced it once...

@rubber_jonnie I'll also try to test my expansion (no RTC) and see how that goes...just in case!

Maximilian wrote: 31 Jan 2025 13:33 If you have a PLCC extraction tool then it could be worth it to extract, inspect and clean the Agnus and the socket.
And check Gary.

You were very unlucky to have corrosion on that connector, I repaired many of these machines and I only replaced it once...

Thanks.

Yep, I will do that, I just haven't got to it yet. It's certainly not the worst I've seen, but it did need the pin header removing and cleaning up as well as the PCB plus fresh solder.