Amiga 600 guru meditation on boot (sometimes)

[gooddwarf]

Hi everyone!

I'm a newbie to the amiga world; I just recently got my hands on an amiga 600, and I have a little problem. Or better, sometimes I have a little problem, and I hope you can give me some clue on what to look for.

The fact is that sometimes (let's say more or less 3 out of 4 times) it boots up normally (at least to the kickstart [the purple screen with the floppy, forgive me if I use wrong terms], but I got it to load workbench 2.05 the first times before I opened it), but at seeming random times during the boot phase I get a guru meditation, with varying error codes (e.g. 8100 0008, 8100 0000,  8000 0004, 8000 0000, 8000 0003), but always in the same task (000026D0). If I press the left mouse button, then it boots ok.

This behaviour happens also with nothing but the motherboard connected.

Oh, and another detail (that might or might not help, I really don't know): occasionally (say... it happened like 4-5 times in about 50 tries, and just once after I reseated the rom chip) the kickstart screen has some messed up colors, with a lot of gray in the zone of the amiga logo and the floppy.

Actually, when I opened it up to check for visible damage, I noticed that a ceramic smd capacitor near the RAM chip (C17B) failed short (and in fact, burnt a hole in the plastic shield below it), so I removed it (I think it is not essential), but to no avail. Everything else looks fine on the board: I checked the traces near the burnt capacitor and everything seems ok.

I'm a newbie to the amiga world, so I really don't know what to do now. As a side note, I haven't recapped it yet, since I really have no idea if that may be the cause of the problemr. I just don't like the fact that sometimes my A600 doesn't boot at totally random times for unknown reasons, and I would like to fix it if it is possible (before doing other things with it, like cleaning it really well, retrobrighting, installing an hdd...).

I really hope someone can give me some hints on what to look next, I'd really like to solve this issue.

I posted it in this section becouse I suspect it is a hardware issue, since it happens with literally nothing else connected by the pcb (and no software loaded). I hope it is the correct one

[gooddwarf]

Thanks for the replies! I'll probably recap the whole thing as soon as possible (since it also has a really really faint audio) and see if that makes a difference. I haven't already done that because the machine most of the time works just fine, and moreover the caps are visually ok.

I also inspected the location near the C17B. Traces are ok. That cap was a decoupling capacitor for the U17 (which should be a ram chip I think). I have no idea how to test the ram is working, but traces around that chip are ok and there are no shorts... or at least I haven't noticed anything wrong inspecting it

[gooddwarf]

I'm sorry for the stupid question, but I'm really a newbie with amigas... how can I make the test program you linked run on the amiga?

Unfortunately replacing the C17B will prove almost impossible, since the pads basically exploded with the capacitor and there is nothing to solder to there. Moreover I don't have any ceramic capacitor lying around. The most I can do would be installing an electrolytic capacitor in its place (by this I mean simply between the first and the last pin of U17), but I don't really think if it worth the trouble (and risk).


Update: I recapped the machine, no noticable difference (even the audio is still very faint). Most capacitors were not really bad. I noticed a few traces under C303 (in particular D15) that were almost black. They tested ok with the multimeter, but I might consider using wire there. The same for a trace just under C334 (near the rca jacks for audio)