Cap replacement advice

[tld]

Hi,

Sorry if this has been covered well elsewhere, I've searched around for a bit (here and on google), finding various bits of thoughts, but would really appreciate some feedback from you guys.

Long story short; There are lots of guides on recapping, but a lot of them sum up the actual dirty work as "Now replace the capacitors", or similar.

Well, that's not always as easy as it might sound.

In the power-supply I'm looking at now, I've got at least two Teapo bad caps. First thing would be to get them out of there (noting polarity offcourse). In this case, positive side is mounted between a coil, and cable hookup. Both of those are sinking heat away from the cap like mad. Negative side is attached to ground-plane, again with a lot of cables.

I've got a Hakko-clone for a soldering-station, about 50-60W or so. Here though, it's hard to get anywhere. It's hard to simply heat the joint and (gently) push out the cap, it's hard to get to the legs to cut them, and so on.

I could take a 120W soldering-gun to the wires, removing them first, wanting with reattaching them until later (if the PSU is successfully revived).

Anyone have any good advice?

Front side:
http://static.inky.ws/image/2874/image.jpg

Back side:
http://static.inky.ws/image/2875/image.jpg

Terje

[mariushm]

Re: Cap replacement advice

Get a hair dryer ..

Use the hair dryer to heat up the back of the pcb in that area for a few minutes until it's nice and warm.

Put your solder iron on the leads of the capacitor and add some leaded solder ... make blobs of solder on the capacitor holes.

Now carefully put your finger on the capacitor on the other side, lay your solder iron as flat as possible on both blobs of solder. Wiggle the capacitor with your finger, one of the leads should pop out of the hole on the other side (usually the + side as the ground tab is sinking heat faster)
Now as you wigle the cap, put the solder iron on that other lead and pull out the capacitor.

60w should be enough.

When you want to plug the new capacitor, warm the blobs and slowly push the lead inside ... you don't want to force them because you don't want the copper to break off the pcb.

You could also try to use some solder wick to "suck" the solder from the holes after capacitor is removed, but I found it easier with such boards to just put the capacitor in... the holes are big enough in diameter that the solder doesn't get stuck in the hole.

ps. you should replace all those 3 teapo on the secondary side, not just the two slightly swollen.

[tld]

Re: Cap replacement advice

Get a hair dryer ..

Use the hair dryer to heat up the back of the pcb in that area for a few minutes until it's nice and warm.

That could perhaps do the trick, and sounds less evil than soldering gun.

Almost tempting to do a setup with peltiers to keep temperature of coil and friends high, while soldering...

I'll give the hairdrier a spin, and see if I can tackle this beast. Thank you very much.

ps. you should replace all those 3 teapo on the secondary side, not just the two slightly swollen.

I was thinking about holding off with the last few caps (there's one or two more, that doesn't show in the photo), until I've changed the bulging ones, making sure I could get this done properly, and seeing if the PSU can be rescued, then replacing the rest if there's hope.

Thinking behind that is to not waste good caps if this is a loosing project anyway, and getting a feel for how hard it'd be to replace the last few caps. If I have to fight all the way through this, risking the board, maybe it'd be better to leave in the last few for now?

Note that the board came from a home-server, and I'm not looking to place it back into active service there, so won't be critical if it'll break at a later point.

Again, thanks for your advice and help.

Terje