Best way to remove a 3296 trimpot? - Page 1
Forum section: electronics / beginners

author: Rick Law
author_rank: Super Contributor
timestamp: April 08, 2013, 06:38:04 am
content: Hi guys, I am trying to benefit from your experience again.What do you think is the best way to remove a 3296 trimpot that is sitting in the middle between two other trimpots?Normally, I would just melt the solder at one leg, rock it a bit, do the same to the other end, rock it more, until the whole thing comes loose. I also wait till the component is removed before suctioning the old solder since I found it harder to melt the little bitty of solder left holding on to the component’s lead. But that involves melting the solder many times as each round loosens it a little more. That was when components are big bigger than a grain of rice and harder to be overheated.With components I do not intend to keep, such as this failed trimpot: before desoldering, I would cut/crush the component right in the middle so I can desolder a leg at a time. I did experience once the cut a component in the middle pulled a leg so much it pull the PCB trace off the PCB.It is rather close to some SMDs which doesn’t stand up to man-handling too well. My soldering skills is rusty. So, with so much experience here, perhaps I can learn from you a better way of doing it.ThanksRick

author: David_AVD
author_rank: Super Contributor
timestamp: April 08, 2013, 06:46:02 am
content: Some "Chip-Quik" low temperature solder will do the job. Add some to each joint and the trim pot will either fall out (or very easily pull out) after all are done.

author: edpalmer42
author_rank: Super Contributor
timestamp: April 08, 2013, 05:30:46 pm
content: Use a tip that's big enough that you can lay it down in line with the three terminals of the pot. Melt all three leads at the same time and pull it out. If necessary, add lots of solder to the terminals to make it easier to melt them all. One big blob of solder works great. Clean up the mess afterward.Ed

author: Rick Law
author_rank: Super Contributor
timestamp: April 08, 2013, 06:58:43 pm
content: Quote from: David_AVD on April 08, 2013, 06:46:02 amThanks! Never knew that "Chip-Quik" existed. The Chip-Quik kit is worth more than what I planned to fix, but I am considering getting some just to teach myself how to do it.Now I am waiting for my cheapo replacement soldering iron. My (really really) old one is near death. That should give me some time to talk myself into getting a Chip-Quik kit to try.Thanks againRick

author: Rick Law
author_rank: Super Contributor
timestamp: April 08, 2013, 07:18:59 pm
content: Quote from: edpalmer42 on April 08, 2013, 05:30:46 pmThat is an interesting idea. Old idea to most of you, but practically new to me - I have been using single-sharp-tip soldering iron all these years my mind never left the box. "Soldering-iron-tip = sharp pointed thing" to me. Silly me.Hack, I can fashion a "three prong soldering iron tip" out of a cheap fork and heat that up with my plumber's soldering torch. That may take some practice, but in theory should work.That sounds fun, I should try it just for the fun of it.Rick

author: Smokey
author_rank: Super Contributor
timestamp: April 08, 2013, 07:25:24 pm
content: Are you talking about the surface mount ones or the through hole ones?For the through holes ones, it's pretty easy. First just use a solder sucker on each pin and if it still sticks, rock it till it breaks free. The wide tip that hits all the pins at once is also a great method, and sometimes faster than the solder sucker but you will still have to suck the solder out afterwards anyway if you plan on replacing it. There are lots of good posts about getting through hole parts off when there is a big thermal mass to overcome if you have that problem. If you don't have a wide tip, you can try blobbing the solder across all the pins and heating the middle of the blob with your small iron.For the surface mount ones, its a little harder especially if it's RIGHT next to another pot and you cant get to all the pads from the sides (this is poor design by the way). You will end up pulling the PCB pads off if you torque it too much sideways and hot air tends to melt these guys if you aren't careful.If you can get to the pads on one side, use wick to get as much solder off as you can first, then heat it up again and bend it up so you can get the pads on the other side from the bottom. This will probably break the pot.If you can totally sacrifice the pot, you can take the hot tip of the iron and stick it into the side of the plastic and heat the lead from the inside. This isn't the best thing for the tips though, so get that stuff off as fast as you can afterwards and it's going to smell like burning plastic because... well .. you are burning a bunch of plastic.

author: Rick Law
author_rank: Super Contributor
timestamp: April 08, 2013, 10:17:20 pm
content: Quote from: Smokey on April 08, 2013, 07:25:24 pmInteresting, that is what used to do until I got tired of fighting with the little bit of solder left but held on hard. I found it very hard to melt that little bit of remaining solder particularly on multi-layered boards. I might have been doing something wrong.Quote from: Smokey on April 08, 2013, 07:25:24 pmI actually had that happened when I cut a (non-SMD, 1/2-1watt) resistor - I did not cut the legs (can't reach) but cut the resistor in the middle using a wire cutter. The cutting introduced some pulling force and that pulled the PCB trace right off the board.Quote from: Smokey on April 08, 2013, 07:25:24 pmThis is a fine idea! I consider the pot dead since the screw is slipping and can't adjust anymore (thus the planned replacement). For this job, this just may be best - no torque/pull introduced by cutting. I have a dead (open belly) soldering iron that I am about to throw out. I use that iron to melt the pot (who cares about plastic left over on a iron I am about to throw out). Once the inside is exposed, I can separate the legs easier.* * *All these are great ideas. In some ways, I am worst than beginners. My electronics experiences was when Apple was merely a fruit, and Bill Gates was Bill Who? Since then, I have done just simple "fix a broken wire" level of electronics. It has been so long since I soldered components, and some of what I do "remember" are too fussy, worst is, some I remember wrong. So I have to relearn some and unlearn some.Thanks guys for sharing your experience.

author: Rick Law
author_rank: Super Contributor
timestamp: April 21, 2013, 04:18:36 am
content: Thanks for your suggestions. The new trimpot arrived in the mail and I successfully replaced it.A week or so ago, I practiced and experimented and found my major issue - I desoldered about 50 components from an old PC (133mhz pentium) without problem. I started desoldering more from a newer dead server board (3ghz) and ran into the problems I was afraid of - I thought about it this time and I understood my problem - lead free solder. My old (normal) soldering iron was not hot enough for those and I stick the soldering tip there so long everything else was melting but the solder I needed to melt.So, instead of using ChipQuik, I ended up first putting some of my old lead-tin solder to improve heat conductivity, use my solder vacuum to suck it all up, and once more adding some old lead-tin solder, and the component came off that server board just fine.Today the trimpot arrived in the mail, I use the same technique to "dilute" the lead-free solder with the lower temperature lead-tin solder and the trimpot came off no-problem. Practice made perfect - I got the new trimpot in within 10 minutes.Thanks for the inputs, guys.

author: amyk
author_rank: Super Contributor
timestamp: April 21, 2013, 08:59:44 am
content: What temperature is your iron set to? Lead-free does need higher temperatures.The "add some molten solder for heat conduction" technique works when using lead-free too.

author: Rick Law
author_rank: Super Contributor
timestamp: April 21, 2013, 06:25:56 pm
content: Quote from: amyk on April 21, 2013, 08:59:44 amMy "main" soldering iron was purchased in 1970's. My other one is a cheapie from Radio-Shack in the 1980/90's both without temperature adjustment.At times, we are so used to doing things a certain way we failed to stop and rethink. I thought of adding molten solder firstonly afterDavid_AVD's suggestion on Chip-Quik and I saw the Chip-Quik video.I felt into that trapwhen stuff would not come off the server mother board. I just got frustrated and forced it. So, I remember I encountered a lot of problems, breaking components, etc. thus trying to learn from others if there is a better way.This time, I had two additional "tools". (1). The idea of adding old tin-lead solder which I know desolder in lieu of Chip-Quik and (2). Use a wider tip, ah and (3) I practiced.I have been away from electronics for very long and I am not sure how committed I am in doing EE things again. As I feel more committed, I will purchase a Scope and a better soldering iron.