Tuesday, February 23, 2010

Bad Capacitor Replacement SUCCESS!

Reduce, Re-use, and Recycle are what we hear a lot, but more important than all of those is REPAIR. Seeing perfectly good equipment hobbled by a few bad parts has always been a sore-point with me (not to mention an affront to Nature).

It's no secret that a huge wave of bad capacitors caused millions of mainboards to suddenly start blue-screening, black-screening, or simply failing to POST.


At my workplace, 100% of our GX270's failed. Most were replaced under warranty.

Even though Dell extended their warranty by a year for affected mainboards (kudos to Dell), we still had several machines go bad after the warranty expired. Being handy with a soldering iron, I had to do something.

To date, I've repaired 12 Dell PC's with a 100% success rate. 5 Precision Pro 650's, 1 SX280, and six GX270's.

The first five boards I repaired, I scrounged up capacitors from other mainboards collected from various recycling houses, RE-PC, 3R-Technologies, etc..

After harvesting caps got old, I decided to just go with new ones, purchased from badcaps.net. (They accidentally shorted me one set of capacitors, but immediately sent me the additional caps as soon as I mentioned it to them - great customer service)

With a dozen machines under my belt, I've learned a thing or two...

My crucial tools:

* Hakko 808 desoldering iron with .8mm tip
* Steinel digital heat-gun (set @ ~510 deg F)
* Weller precision digital soldering iron (set to ~750 deg F)
* Glove for capacitor-pulling hand
* grounding wrist-strap
* PanaVise PC board holder

My tried and true procedures:

(I'm going to focus on the actual soldering, not the crucial organizational things like taking pictures, making sure you've got the right caps, holes, polarity, etc.. By this point, the board is mounted in a vise, the anti-static wrist strap is on, irons are preheated, etc..)

1) PLAN capacitor removal path - the general idea is to heat one leg, pull it out partly, and then heat the other leg, pull it out fully, go back to heating the first leg, and pulling it out. Here, you need to make SURE that you have enough wiggle-room to lean the capacitor a little for the first leg, and then lean it all the way over for the second leg. You don't want to move the cap halfway only to have it blocked and frozen in place.

2) pre-heat work-area on board with heat-gun - this is especially important if the caps are near large ground or power planes on the board that soak up heat. I set the heat-gun at 510 degrees F and heat the area of the board until it's about 270F.

3) heat the first leg with the desoldering tool (don't suck the solder yet) and pull it out partly ~1mm, leaving a little wire nub at the top to heat during the second pass on this leg. This will leave the capacitor leaning a bit and will allow you to lean the capacitor all the way over when removing the second leg.

4) heat the second leg FULLY, and pull it OUT by leaning the capacitor over fully in ONE SMOOTH MOVE. Full heating and one smooth pull is important, because you don't want the solder freezing up half-way out. If you're using the solder sucker to heat the legs, NOW is the time to suck the solder on this pad - while the sucker nozzle is still on the fully heated pad, and the capacitor leg is out. Suck!

5) with the second leg out, go back to the first leg and heat it FULLY. Once it's heated and starts to wiggle, you'll have to wiggle it out. The leg will be bent, so it may take some finessing to remove. Once the leg is out, leave the sucker iron tip on the hole and suck the solder out.

Voila! Capacitor removed!

Important tips:

* Avoid oopsies burning/melting neighboring components with the iron.

* Usually, the positive lead (square pad) on the mainboard is attached to a big power-plane, so you'll need to heat it up a bit more to compensate for the heat-sinking effect of the mainboard. This is where the heat-gun saves the day.

* Do not leave the iron on the pad for too long - you may de-laminate the copper trace from the board, which is FATAL to the repair job.

* Use the glove on your capacitor-pulling hand so you don't burn your fingers or have to go hands-off right in the middle of a pull.

* Don't force the pull! Let the solder melt FULLY. If you don't heat fully and then force the pull, you may have melted the solder on the bottom of the board, but not the top. If you force the pull in this condition, you can pull the top trace off the board, KILLING your repair job.

* Make SURE you're grabbing the correct capacitor! Many caps are adjacent to others. It's easy to grab the wrong cap and think "why won't this wiggle?!?", while overheating the correct one.


These instructions assume you're using the Hakko 808 solder sucking iron. Other tutorials out there describe more appropriate methods if you don't have such a (handy) tool.

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