Bad capaciter replacement

[lowongas]

Has anyone here replaced them sucessfully?
I tried once and couldn't even get them off.
Is there a special soldering gun to do this?
Maybee mine didn't get hot enough.
Mike

[PrntRhd]

That is a possibility, you do want to use a solder wick/sucker to remove excess solder from the joint after you get the connection hot.
Once you get both connections almost clean of solder, just a touch of the heat will free the component from the board.

[larrymoencurly]

You may want to check BadCaps.net (http://www.badcaps.net), under "Recapping Tutorials" and also in their forums, especially the "Frequently Asked Questions" forum. Also YouTube has instructional videos about soldering and desoldering.

I'm going to say that you're right about the insufficient heat because motherboards are made with 4-6 layers of copper, which can really soak up heat, but worse, the capacitors are attached to the inner layers that absorb the most heat because they contain the most copper. 25-35 watt irons are too weak to melt the solder quickly and thoroughly, but a 40-50W iron may be good enough, at least if you wait 30-60 seconds between each use to let the tip completely heat up again. It helps a LOT to keep the tip clean by frequently wiping it and recoating it with solder, and chisel-shaped tips (look like a flat-bladed screwdrivers) transfer heat better than cone-shaped tips do.

Do not use a soldering gun because it will put out too much power and overheat (temperature is not the same as heat power) the glue bonding the copper to the fiberglass. There are 40-70W, temperature regulated irons that are great, and some are pretty cheap. But be careful when buying them off eBay because many are made for 220 volts and also shoddy/dangerous.

If your mobo was made with lead-free solder (do you see "RoHS" anywhere?), even more heat is needed because it melts at something like 450 degs. F instead of the 380F or so for normal 60% tin, 40% lead solder. But you may be able to melt it without a more powerful soldering iron by applying regular solder to the joint before trying to remove the component. That can also help when working with boards made with lead-bearing solder.

Some people remove capacitors by alternatingly melting the solder on each pin and rocking the cap the opposite way each time, but others apply heat to both pins and pull the cap straight out. A safer method is to cut the capacitor off on the component side and individually unsolder each pin (better to be drastic to a bad capacitor than to a circuit board).

Solder can be removed by sucking it up with a hand vacuum device or absorbing it with copper desoldering braid, but there's disagreement over which method is better. Rubber solder sucking bulbs don't suck strongly, while spring-loaded plunger suckers pull strong vacuum but sometimes knock against the circuit board and dislodge copper traces. Copper desoldering braid requires more heat than vacuum pumps do, and to minimize the amount of heat needed, cut off any section of braid just after it's soaked up solder because any used braid left dangling will act as a heatsink and draw heat away from the next joint you try to unsolder. Also use the narrowest braid that will absorb all the solder on the joint because overly wide braid draws away too much heat and keeps the solder from melting, while braid that's too narrow will leave some solder in the hole, where the braid won't be able to reach the remaining solder (will have to apply new solder and start over). 0.70" - 0.85" is about the right width. Whether you remove the solder with braid or a vacuum pump, wiggle the pins side to side to make sure they're completely detached before pulling out the capacitor; otherwise you could rip out a copper trace.

Radio Shack sells an $11 desoldering iron with hand vacuum pump, #64-2060, and it works great, at least on 2-layer circuit boards, but you have to frequently unclog its hollow tip by inserting a #18 solid wire in its hold (as well as clean off the tip. After it's soaked up some solder, don't squeeze the bulb again, except into a tin can, or you'll spray out molten solder -- dangerous and messy. Some people have modified this desoldering iron by hooking it up to an electric vacuum pump, a large vacuum tank, or even a foot-operated tire pump with the check valve reversed so it pulls vacuum instead of pushes air.

First practice on some junked circuit boards, but be sure they're the 4-6 layer type because 1-2-layer boards are so much easier to desolder that they won't give you realistic experience with mobos.

[lowongas]

thanks, I'll try it just for fun
Mike