Faulty A600, diagnostic help needed.

[Freakyweakywoo]

Just got my hands on a A600 (freebie) after running power through it for a couple of minutes it froze, the keyboard still responded so I soft reset but it wouldn’t go back to the boot screen (black screen, not checking for a floppy disk). After leaving it off for a few minutes it boots back up okay, only to freeze up again a few minutes later (the floating disk is frozen in place and it stops checking for a floppy disk).

I took out the exp ram, same problem. I put in a brand new Rom chip, same problem. I have tried it with a HD and without, but always it freezes up after a few minutes. I'm guessing something is getting too hot or is just plain faulty but I don’t have enough hardware knowledge to track down what it could be.

So step up and play guess the fault

[Jope]

Try applying pressure to one chip at a time after it's crashed and then resetting, to see if it's a broken solder joint on one of the surface mounted chips.

[Overdoc]

Also check it with another power supply if you have one.
You can also try spraying cold-spray on each of the chips seperately to track down such overheat problems.

[BinoX]

When you say brand new rom chips I assume you mean kickstart 3.1..

I had a problem with kickstart 3.1 and old hard drives... sometimes the hard drive would loose power for a fraction of a second and then the amiga wouldn't go back on without a cold reboot...

Maybe it's that?

[Freakyweakywoo]

Thanks guys.

Binox, the problem occurs both with and without a HD connected.
Jope, I tried applying pressure to all the chips to see if I could spot a loose one, they are all very securely attached but I did notice the processor, was very hot to the touch though, which brings me to...
Overdoc, I let the system cool off and powered up again, I noticed that before it locks up the floating disk animation starts to jump. At that point I cooled the processor; it started running fine again for about another minute or so after cooling.


Question is, as I don’t have another PSU is it a faulty processor or a faulty PSU?


I ran an A500 off this PSU for half an hour this morning without any trouble, but that still doesn’t convince me it’s not the PSU. But maybe that’s because I'd rather replace a PSU than have to deal with a faulty processor.

[Overdoc]

Unfortunately, this sounds very much like a bad/weak processor.

Anyway, if you have a multimeter you could measure your psu on the pins of the connector, although I don't think it is the problem.
Voltages should be 5V_DC, 12V_DC and -12V_DC. Without load a good psu could even measure voltages as high as about 6,5V instead 5V and up to 16V instead of the 12V. This is just normal.

You can try applying a cooling metal with heat-conduction paste to the processor of your A-600 - maybe it helps ? Otherwise you would have to desolder it, which is little bit tricky if you don't have the right equipment. You will need some sort of adapter for your soldering iron, similar to tweezers, which should measure about the size of the square 68000 PLCC chip.
Then it is more easy than desoldering a 'normal' chip in DIP. package.

[Jope]

You can get the PLCC chip out without an SMT station by using a stanley knife and a normal soldering iron.

Go one pin at a time.. First heat the pin to melt the solder and then immediately, applying Very Light Force, bend it up with the knife.

The solder paste must be molten, but you mustn't over heat the Amiga's motherboard, so you need to be careful here. Previous soldering experience is always a positive thing. :-)

If the pin doesn't seem to bend up easily or move at all, heat it some more! If you force it up but didn't get it warm enough, the pads lift up from your motherboard, and repairing it will be again more difficult.

Check the power supply too, no point in frying another CPU if it gives out too many volts.

I suggest you measure the positive voltages from the drive's power cable with the machine turned on, there's no point in measuring a power supply that is not loaded.