Painted myself into a soldering corner - Page 1
Forum section: electronics / beginners

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 31, 2015, 01:53:55 am
content: I'm trying to replace a couple of caps in a Dell monitor. I have the old caps out (via the rocking method while heating the lands). In the process, 3 or 4 of the holes are full of solder. I have no wick, but I do have a spring loaded solder sucker device. After quite a few attempts, I've been unable to clear the holes, so that I can put the new caps in. I think the board is a 4-layer, and I am being a bit cautious about hitting it with too much heat. The Hakko is currently at 750 with a chisel tip inserted.Is there some basic maneuver I am missing here ?

author: DavidDLC
author_rank: Frequent Contributor
timestamp: March 31, 2015, 01:56:03 am
content: Get a big needle, melt the solder and use the needle to clean the hole.That most of the time works for me.David

author: xrunner
author_rank: Super Contributor
timestamp: March 31, 2015, 01:58:42 am
content: Make sure the holes are really full of solder (you seemed to say they were) . If they aren't put more solder in. Heat the hole on one side of the board and suck it from the other side. Make sure the heat travels all the way through, but don't sit on it for too long. Make sure the sucker is tight on the other side. Should work.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 31, 2015, 02:04:21 am
content: Would adding some flux make this easier ?

author: pickle9000
author_rank: Super Contributor
timestamp: March 31, 2015, 02:07:17 am
content: A preheater is a big help, stainless needle, iron and sucker on high mass copper side, last resort a pin vise undersized drill and a gentle touch.

author: bson
author_rank: Unknown
timestamp: March 31, 2015, 02:22:16 am
content: What xrunner said... make sure the sucker pulls air through the hole and heat it from the other side.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 31, 2015, 02:41:54 am
content: Quote from: bson on March 31, 2015, 02:22:16 amThat has solved the problem.I had no vise to hold the board, so that I could get at both sides. A quick substitute was 2 heavy cookbooks on one side plus a cookbook and some ceramic tiles on the other. That was sufficient mass to keep it upright.Thank you to everyone !

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 31, 2015, 03:23:53 am
content: Initial tests indicate that the cap replacement was a success. The monitor is a Dell 2005FPW, and the caps were a pair of 470 uF 16V caps, replaced with 470 uF 25V Nichicon. The monitor is one I purchased in 2005, and gifted it to my mother about 4 years ago. She noticed vertical rolling a while back. Cap replacement has extended the life of this monitor.

author: Fat
author_rank: Regular Contributor
timestamp: March 31, 2015, 04:59:21 am
content: Nicely done.

author: cosmicray
author_rank: Frequent Contributor
timestamp: March 31, 2015, 12:31:41 pm
content: Quote from: evb149 on March 31, 2015, 05:25:16 amIt was a long shot, and based on a video on youtube of someone doing the same repair (more or less). Worse case, the monitor was a write off. As I am heading towards a place that has a room of used monitors today, I was hoping to make a repair determination last night. The caps that were removed were 'Sam Young' manf, that showed no exterior signs of deterioration. The replacements were Nichicon . Apparently there are several capacitor based failure modes with that monitor, and likely based on the vintage of the caps.The video briefly shows some disassembly steps. The badcaps site has the Dell repair manual as a pdf, but even that is somewhat incomplete on disassembly . Getting the interlocks (that hold the front bezel together) to release is incredibly hard. My first attempt almost resulted in torn flesh. The key was an extremely handy tool I found in a junk shop about 10 years ago, a Cuisinart nylon bowl scraper. It is extremely tough, and has a sharp edge, that allowed me to get under the bezel edge, and apply enough force to snap loose the interlocks. obtained off eBay, from a guy in Cocoa FL. The listing said 6 caps, he sent me 10. I strongly suggest a number of small paper cups (~1 oz) to keep the various screws organized.The repair video is here ...

author: TimFox
author_rank: Super Contributor
timestamp: March 31, 2015, 12:40:23 pm
content: I find that a normal toothpick makes a good hole cleaner.

author: senso
author_rank: Frequent Contributor
timestamp: March 31, 2015, 01:23:22 pm
content: The other option is to grab the cap, heat the solder filled hole and mount the cap, no need to clean both holes.