A1200 dead no life.

Hi,


I recently decided to try my A1200 that i haven't used for at least 15yrs in the loft.
The A1200 was using a modded ATX power supply and an Apollo 1240 card, The A1200 showed no signs of life at all so i stripped it down and took out the motherboard.
On the underside of the board what i believe is the 5v trace, the centre of it is bare copper.
I don't have access the a decent multi meter but all the 4 main connections to what i think is the power filter coil they all show continuity to earth.


Could this be because of a dead power filter? if so were can theses be sourced.



Many thanks

[Daedalus]

Are you sure it's not the PSU? You really need a multimeter to be able to troubleshoot that. So, no power LED at all? The bare copper trace, where is that? There aren't many 5V traces on the surface of the board, most are made via an internal layer.

I can't see it being the choke, unless something crazy has happened, but that would show other damage too I suspect. For a simple continuity check, the choke should show almost no resistance between its input and the corresponding output. Are you trying it with nothing attached other than the PSU and LEDs? Not even a floppy drive.

There is no life at at all from the board, i took out the board with just the led attached.
the psu voltages are pretty much spot on with the cheapo multi meter i have, 4.98v 12.4v -12.2v

the trace that is exposed is from C800 to LF1 pin 2 there's is a small circle in that trace that appears broken.

[ajk]

Perhaps you could take a couple of good close-up photos of that area of the PCB? Would be easier for the rest of us to troubleshoot.

[Daedalus]

Hmmm, it's possible that the capacitor C800 has failed short and that's pulling the whole PSU down. That would also overheat the traces and damage the coating, but there might not be enough current available to melt the trace altogether. If the trace is broken, there must be something else wrong as that would act like a fuse, removing the shorted capacitor from the circuit.

This is how i found it i haven't used the Amiga for 16-20 yrs possibly more tbh.

[Daedalus]

Ah, I see... Yep, that'll totally kill the machine alright - that's the main 5V supply and not just to C800, so something else has shorted and allowed that trace to burn through. It's possible to do that with a badly connected peripheral - possibly a floppy drive with the power connector forced on one pin out of position. Was it possible that the motherboard shorted against the case at any point?

I have no idea tbh, was working perfectly many moons ago, so i take it this is beyond repair then?

[ajk]

The repair of that trace is trivial, a wire soldered across those points will do; but the big questions are:

1) what caused that trace to burn, and does the problem still exist on the board
2) did any components also suffer damage when this happened

You'd probably be best off sending the board to someone nearby who has experience working on Amigas. Troubleshooting this kind of thing over forum posts will be slow and difficult

Do you know of anyone in the North West UK that might help, or anyone the forums that is specialized to fix it?

[Daedalus]

I have a list of some of the guys who do repairs here: http://robthenerd.com/amiga/repairers

There's Russel Cowell in Liverpool that might be close enough to you...

[project23]

The copper on the trace looks like it hasn't corroded, so I would guess that it burned through when you powered it up, acting as a fuse as mentioned above.

You mentioned all the rails show continuity to ground - is this still the case? Check the 12, -12, and 5v rails against ground. Check before and *after* the break.

If they all show continuity to ground, I would have to guess that something conductive has found its way into the case or the floppy after all these years, and is shorting everything out.

If it is just one line that is shorted to ground, then it's possible that a capacitor has failed short - though I believe this is quite rare.

There'll be someone in the north west experienced enough to help you, for sure. I'm in the north west myself but don't consider myself experienced enough to actually fix this for you. It's a good community this, you'll find someone!

Good luck!

John