Sad Amiga - Possible memory issues?

[camsoft2000]

Originally Posted by indigolemon

Have a read of this: https://retrohax.net/amiga-500-mods-2/

Specifically - one of the machines Drygol deals with he has to adjust pins on the Agnus to deal with symptoms that sound very like yours.

That’s helpful, tbh the PLCC socket and pins look in very good state but I’ll check again. The Amiga was in pristine condition, you can tell from the case it’s been in dry storage for a long time.

Going to give the entire thing a good clean and check all the chip pins.

[camsoft2000]

Right so I’ve removed every chip, throughly cleaned the board with contact cleaner, cleaned all the pins on all the chips with a fibreglass pencil, pulled out all the pins on the PLCC socket and same on the Agnus chip to ensure good contact, I’m pretty confident the chips and connections are good on inspection, checked soldering on board and it’s all shiny nothing dull.

And....

It hasn’t made a blind bit of difference. I’m ready to throw this machine out the window, I’ve pretty much lost all my excitement and enthusiasm that I had when I bought my first and now probably last Amiga.

I’m not an electrical engineer so I’m at a loss how to proceed. Can’t find any board schematics for the rev5 A500 and if I did I’m not sure what I would do next.

I’ve spent £100s on this machine now, hours and hours of time and got nowhere.

I’m going to make an assumption I’ve even got a power issue, or a bad chip somewhere.

But I just can’t just replace each chip one by one I need to narrow down the issue otherwise I could just end up throwing more time and money at it and get nowhere.

I’m totally deflated and disappointed.

[solarmon]

In your original post said you only ran the memory test in Amiga Test Kit for 10 minutes. This is nowhere near long enough, especially for that amount of memory.

I would leave a memory test for several hours at least to make sure it covers every bit of memory - as the memory test, as I believe it, is random.

Do the other health checks in Amiga Test Kit run OK, especially CIA tests?

[camsoft2000]

Originally Posted by solarmon

In your original post said you only ran the memory test in Amiga Test Kit for 10 minutes. This is nowhere near long enough, especially for that amount of memory.

I would leave a memory test for several hours at least to make sure it covers every bit of memory - as the memory test, as I believe it, is random.

Do the other health checks in Amiga Test Kit run OK, especially CIA tests?

I ran it a bit longer did over 100 iterations after I wrote the post but yeah I guess I could run it again.

All other tests passed fine.

[cmorley]

The revision 5 schematics are in the A500 Techincal Reference Manual at the back.

[camsoft2000]

So I received my DiagROM today but it all checked out as far as I could tell and seemed to confirm what AmigaTestKit had already told me. Memory, CIA, IRQ tests all pass. Though it did fail on the extended memory test which I’ve read is because it tries to read up to 2MB of chip RAM. I’ve only got 1MB.

Also opened the power supply and visually inspected it and it looks mint inside kind of like the Amiga itself, it’s clearly been well stored for a long time.

I tested the voltages:

-12v was -10.14v
+5v was +5.22v
+12v was +11.78v

The +5 and +12v are within tolerable levels as per http://www.ianstedman.co.uk/Amiga/am..._supplies.html

The -12v is puzzling, maybe I was testing it wrong but it was giving a reading of -10v which is way out.

That said I was testing directly off pins and not under load but other readings were within expected tolerances.

I’m not convinced it’s a power issue, just the crashing tends to happen when doing pretty much nothing just moving the mouse and dragging a window in Workbench (if I can even get it to load) will cause it to crash. Screen freezes and then goes blank followed by guru.

Still need to test the memory voltage rails as suggested by Chris, running the memory tests always passes though and the computer has never crashed once when running diagnostic software.

[camsoft2000]

Just wondering could this be a graphics issue, would a faulty Denise cause gurus or would we expect just graphical artificial issues?

[Daedalus]

Originally Posted by solarmon

I would leave a memory test for several hours at least to make sure it covers every bit of memory - as the memory test, as I believe it, is random.

Just to clarify here, Amiga Test Kit tests *all* memory in every cycle, not just random spot checks. It can't of course check the small amount of memory used by ATK itself, but everything else is checked each time.

Running multiple cycles is still very much advised, because there could still be something marginal that only happens once in a while, but chances are if there's a fault that's regularly causing crashing within a couple of minutes, it would also show up in ATK within a few minutes.

[camsoft2000]

Originally Posted by Daedalus

Just to clarify here, Amiga Test Kit tests *all* memory in every cycle, not just random spot checks. It can't of course check the small amount of memory used by ATK itself, but everything else is checked each time.

Running multiple cycles is still very much advised, because there could still be something marginal that only happens once in a while, but chances are if there's a fault that's regularly causing crashing within a couple of minutes, it would also show up in ATK within a few minutes.

Exactly. I ran it for a good 30 minutes and it all passed. Crashing is pretty much guaranteed when running software apart from a few small games within a 20 seconds of so so I would have expected to see memory issues in my tests.

It’s definitely a stability issue issue and sometimes loads workbench and sometimes does but will always crash at some point generally fairly quickly.

Still feels like a power issue but it’s odd that some software generally single disk software doesn’t seem to crash.

I can play Arkanoid no problem, I can run test software no problem. Load or use Workbench not a chance, play Lemmings not a chance will load all the way to the game’s first level and then it will crash after a few seconds of play. Other tools also crash. AmigaDos will crash if I attempt to use it for a while. It will crash just moving the mouse or dragging a window

Very odd.

Anyway I’ve bought a rev6a board off eBay so going to swap that out. If that doesn’t fix it then has to be one of the chips I guess.

[camsoft2000]

Update, Sad Amiga is now happy Amiga. Seems I had a bad Amiga Forever 3.x ROM. Put in a 3.1 KS and no more crashes and all my software now works in including workbench.

Thanks everyone for help and advice on this, learnt loads. Special thanks to [mention]indigolemon [/mention]for pointing me in the right direction.

[indigolemon]

Glad you got it working in the end! Another strike against the nightmare that is the 3.X ROM