Replacing Caps in a 600

[Damion]

Chartus wrote:
Whats the easiest way to replace the SMD capacitors on a 600.  Some of them are in tight places.  Is there any way to maybe snip them off without hurting the motherboard?

The safest way is hot air. Personally, I apply a smidge of fresh solder, heat one side at a time, and gently wiggle the cap a small amount one side at a time (with a small screwdriver) in one direction, until it comes off. A good quality iron (I use a Hakko 937) is a must. Although it looks impossible, replacing the audio caps isn't too difficult with the right sized tips, a steady hand and lots of patience.

If you're careful, you won't lift pads... unless the joints are already damaged from the electrolyte, in which case some additional repair may be unavoidable. TBH I haven't yet found the best method for dealing with heavily corroded joints/pads. Best thing is to get to them before you have to worry about that.

Some people replace with tantalum caps, I simply order the original type in a quality brand (Panasonic) since I'm a stickler for originality.

@alexh

IMHO - EVERY single one should be replaced. I've found that with the Commodore-era A1200/A600, they've all leaked a bit, even if there are no visible signs. Every one on my A1200 and A600 boards emitted that tell-tale "fishy" odor during removal. The caps on my Escom A1200 seemed to be OK, but I replaced them anyway after witnessing what nasty things can happen when they leak... two seriously fux'd A600 motherboards in my case :boohoo:

Probably not really necessary to replace the thru-hole caps, but I do anyway with a quality replacement (like Chemi-Con KZE series) while I'm at it with the others.

There's a link on this page to the A600 schematics, which list all the needed caps. (I could post the Digi-Key part numbers for anyone in the US who wants to order them without the hassle of looking everything up.) The A1200 uses all the same caps, so order a bunch and do them all. :-)

-edit-

Just thought I'd add, there's some fantastic info on this subject here. Really saved me from making a mess of things!

[Damion]

A couple (crappy) shots of an A1200 I did:

pic 1

pic 2

The light reflection makes the solder joints appear a bit "blobbish", but they look OK in person. ;-)

[Damion]

alexh wrote:

-D- wrote:
IMHO - EVERY single one should be replaced. There's a link on this page to the A600 schematics, which list all the needed caps.

Erm thanks, big help. How many are there on an A600?

There are around 20 total (including the 4 big thru-hole caps), the amount and values are spelled out clearly in the schematics.

I'm not sure I really believe you that all the capacitors are susceptible to failure and I dont think I (or anyone?) could be arsed to replace them all? Could they? It would take hours. Not to mention the high risk to most users of a mistake.

I can only go by what I've seen, which is that they leak at random and not just the audio caps as is oft-repeated. *All* of them had leaked to some degree on my C= made A1200. Random locations on two A600 boards (audio caps fine on both of those). Escom board was fine, but is also newer.

It does take a little time to replace them, but things go quickly after getting the hang of it. Less than an hour a board I would say. And I agree - there absolutely is a risk (particularly if the leaked electrolyte has had a chance to cause damage) and I stress that sending the board to an expert like Anthony Hoffman (Castellen) is probably a real good idea.

You think the failures are just due to poor quality capacitors and buying top quality will fix for the future? Not that they were the wrong values / type / power rating?

Unfortunately I can't say, maybe an expert can chime in. From my amateur perspective, the quality of the caps used by C= was poor, especially considering the random nature of those that leak. I noted from earlier posts by Castellen that he uses the original type/rating in a quality brand, so I went with that.

When they eventually break I guess I'll bin them and just use WinUAE :-(

It's no biggie, a couple of evenings and you can have all those POS caps replaced. I bet you'll get tired of having all that old junk set up around the house long before it actually breaks. ;-)

[Damion]

A1200:

5 x 22uF, 25v (or 35v)

2 x 47uF, 16v

4 x 100uF, 6.3v

3 x 10uF, 25v (some have 4)

The thru-hole caps are 2 each 470uF, 16v and 1000uF, 10v.

[Damion]

No worries, check your PM :-)