Trying to repair my A600 - blown cap

[storml219]

Hi all,

Hope you can help me trying to restore my A600 (Rev 1.5) to good health.

I have (what it seemed) a pristine A600. Maybe it was my mind playing tricks on me, but I felt the color of the boot screen was not what I remembered back in the day (but then again, I'm color blind ). Another fishy thing is that it seemed to have the left and right audio channels reversed (i.e., left was playing right, and right was playing left). A couple of months ago, I thought it was a good time to open it (it was never been opened before) to give it a good clean and also install a 44-pin CF to IDE adapter and also a 3.1KS. It booted and ran along as always but I've never got the CF to work, despite multiple tries and possible solutions. I've decided it was time for a compete recap.

with a help of a friend with better soldering iron skills than me (but admittedly none of us is a pro), we have changed all caps, cleaning the PCB in the process and inspected the tracks. I've turned the A600 on, it booted and it ran fine, but no CF still and the boot screen add the same color as before the recap. All the sudden, the machine turned off and there was this funny smell… we turned it on again, and this time no boot, black screen and the caps lock light continuously blipping (not 1, 2, 3 or 4 flash and pause - just blipping in loop).

I've opened it again, powered it again and saw a spark under C307, which we have changed.

https://photos.app.goo.gl/XpDUeUNBfGMwJStB8

Turned off and found that E561C cap blown (and maybe the two caps next to it are also affected C592 and E556C). I've attached a picture for you to see the damage.
https://photos.app.goo.gl/7oEiPzDWhiiGwmUo6

As for the smell:
https://photos.app.goo.gl/fy63Z8ftorQ4BxvD6

I reckon E561 is related with RS232 (+12V) an close to U8, and the other two are relate with the floppy power and U29 (but these might not be affected). Did I just ruin everything ? The next steps will be to remove this (these?) cap(s) and have a good clean around the area and make a very close inspection of all the tracks and values with the multimeter . But what worries me the most is to try to understand what cause this, because if the source of the problem is not identified it will happen again and/or in other areas and, possibly, further damages, perhaps beyond repair. Was it a short, or can there be more issues as the cause, such as some bad custom IC (Paula? - after all C307 is related audio power) or CIA? and this has not been detected before because the capacitors were already bad? can this be related with the funny issues with the sound and never been able to use the CF (in this case I was thinking it was my own lack of skills).

Thanks so much!

Best,

[solarmon]

E561C is very close to the legs of C701 C307, and the +5V, +12V, -12V and GND rails are very close around C701 C307 - so it is likely that there is a short around there.

Use a multimeter to check for shorts between the power rails (+5V, +12V , -12V and GND). I would desolder C701 C307 and clean the area, checking for shorts without it in.

EDITED to correct C701 to C307

[storml219]

Originally Posted by solarmon

E561C is very close to the legs of C701, and the +5V, +12V, -12V and GND rails are very close around C701 - so it is likely that there is a short around there.

Use a mutimeter to check for shorts between the power rails (+5V, +12V , -12V and GND). I would desolder C701 and clean the area, checking for shorts without it in.

Thank you so much for the feedback and help!! will do that. I hope it is a short. (just to be sure: you mean C701 or the C307? the C307 is the one on the upper side of the mobo, directly above E561, so its legs are very close to E561)

[solarmon]

Originally Posted by storml219

Thank you so much for the feedback and help!! will do that. I hope it is a short. (just to be sure: you mean C701 or the C307? the C307 is the one on the upper side of the mobo, directly above E561, so its legs are very close to E561)

Apologies, yes I meant C307.

[storml219]

Originally Posted by solarmon

Apologies, yes I meant C307.

many thanks again! next week I'll get back into it (to much work these days) and post the findings

[storml219]

Originally Posted by storml219

many thanks again! next week I'll get back into it (to much work these days) and post the findings

Just a quick status update: IT'S ALIVE
thank you for your help.
The cap burned and made quite the damage to the ground track… it was due to, most probably, a short with the C307 legs or some dirt. what we did was to replace the cap and get the ground from somewhere else on the mobo with a wire (all proper DYI ) and it's alive again. The thing now is that I can not get the CF (to IDE) to work…

Thanks everyone and specially solarmon