Weird A500 issue

[stevew]

I've got a rev 6a board that has a weird issue.

I played Mircoprose GP on it and completed 7 laps :-) Then went to load the Amiga Format Octamed demo from disk, and got an error whilst loading, whilst a loud audio hum was present, at this time the mouse did not respond, it's like whatever was causing the hum was causing to the CPU to freeze, or interrupts to stop. Restarted Amiga, disk stared to load, hum noise again, Amiga froze, then disk carried on loading and I saw the error again.

Restarted and now grey screen and loud audio hum. Removed CIA, Gary and Paula and replaced, still the same issue.

When this happened yesterday I took out both CIA's and cleaned the sockets and chip legs with IPA and replaced the CIA's, I did the same to Paula and Gary. Once I did this the Amiga started to work again, but only for a short time.

I have tried other CIA's, but this did not fix the issue.

Reading up a bit on vectors after looking at error (attached) it seems it maybe an interrupt issue.

I took the CPU out to find pins 1 and 2 were bent and not in the socket, I've straightened these and replaced the CPU, but these are Data 3 and 4 pins.

I'm wondering what would could cause the loud audio hum and freezing of the Amiga.

[Rebate]

Hi
Is the sound coming out of the speakers?
Regards

[demolition]

The audio hum is probably caused by the machine freezing which means that it keeps playing the same audio buffer that doesn't get updated.

The reset vector is in chip RAM or in KS ROM after a reset so my guess is that you may have some faulty memory. If you can get it to boot, you could try running a memtest program like MBRTEST-2.

[stevew]

Thanks for the replies. I reflowed most of the board this morning, now it seems to be working again. I was just wondering where the issue may be, to help troubleshoot. So maybe a dry joint on the rom chip socket.

[stevew]

Originally Posted by Rebate

Hi
Is the sound coming out of the speakers?
Regards

Yes though the TV Speakers

[stevew]

After several hours testing, the Amiga froze again, just stopped with excess audio noise. Restarted Amiga, no guru message, so not a software or hardware fault.

Loaded and played F1gp again and on lap 7 (roughly where I had got to before) it froze again. This time I pressed down on Paula and the game started again, although with no sound.

[AmigaHope]

I concur with the bad RAM assessment, run a memory test.

[stevew]

Originally Posted by AmigaHope

I concur with the bad RAM assessment, run a memory test.

Memory tests run fine, more like the interrupt is freezing. If it was an address error the game will crash.

The address of the errors I did get, pointed to the expansion, which is a brand new one from Amigakit. It also did it on my a501

I've replaced the Paula socket, just tested with f1gp for 2 hours, so far so good. I'll continue testing.