safe way to remove large smd caps - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: November 16, 2024, 08:21:03 pm
content: Hi,I have a board with five, 22uf electrolytic SMD caps that are sort of close together. They are surrounded by a lot of smaller devices that I can't afford to move as I have a bad tremor. I have hot air in different formats but heating that whole area is risky for me because if any of the smaller devices move, I doubt I could solder them back into place. I was wondering if I heated the entire cap outer shell if they would lift off? I dont mind destroying the caps as one or two are suspect. Any other ways to get them off? I've had SMD caps that have long PCB traces under them cause problems too.thanksJerry

author: voltsandjolts
author_rank: Unknown
timestamp: November 16, 2024, 08:28:07 pm
content: Have you got two soldering irons, one for each end of the cap?

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 16, 2024, 08:46:10 pm
content: Get a pair of side cutters, grip the body of the cap, and twist it maybe 2 or 3 revolutions until it breaks off.This leaves the soldered leads on the PCB pads without damaging anything.Then you can wipe the leads off the pads with a soldering iron.This sounds kind of brutal, but it works.https://www.youtube.com/shorts/z7ZkzVe1ySs

author: u666sa
author_rank: Frequent Contributor
timestamp: November 16, 2024, 09:56:19 pm
content: Apply flux for flow. Apply low melt solder. Remove.

author: cncjerry
author_rank: Unknown
timestamp: November 16, 2024, 10:58:12 pm
content: I tried two soldering irons today and the issue is I need two hands when using my right hand as my tremor is really bad.I like the twisting idea, just hope I don't lift any pads. Is that pretty safe? I have really good tools for trimming, cutting, etc.

author: cncjerry
author_rank: Unknown
timestamp: November 16, 2024, 11:07:16 pm
content: i have a 2nd board that has a power problem so I tried the twist-off on that one and it worked perfectly! thanksby the way, so far 8 of 10 are bad...

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 16, 2024, 11:27:11 pm
content: I have done hundreds of these (e.g. re-cap a maninboard) and not lifted a pad as far as I remember.I know it kind of goes against all your instincts, but you get over that.

author: cncjerry
author_rank: Unknown
timestamp: November 17, 2024, 01:27:34 am
content: looks like I need to replace more caps. What are the caps called that have radial leads with an outer rectangular casing? Both leads stick out one of the narrow sides of the rectangular casing. This thing has a bunch of them. The electrolytics I replaced were 90% bad, had a little leakage under the case, and if they had a reading, it was low. I have to go back to the schematic now.Jerry

author: Harry_22
author_rank: Frequent Contributor
timestamp: November 17, 2024, 01:58:11 am
content: Quote from: cncjerry on November 16, 2024, 10:58:12 pmHi Jerry!Try to relax your hands.It's not easy. Place their elbows on the table and do not strain. You won't damage anything. Maintain inner harmony. Over time, everything will get better and your hands will stop shaking.Everyone who starts soldering BGAs goes through this. Rolling balls for instance, helps improve fine motor skills.Don’t forget about the bottom preheating.@u666sa, very good advice. Modern lead-free solders are very refractory. It's lazy to get Rose's alloy every time but there should be lead solder.@Audiorepair, many thanks! I will use your advice. Before this I only pulled off regular caps by force so as not to waste time lifting the board.PSFeel free to post photos, you'll entertain us a little

author: cncjerry
author_rank: Unknown
timestamp: November 17, 2024, 06:58:13 pm
content: I've been soldering for over 50yrs but developed a really bad tremor in my right hand and the only way for me to solder now is to stabilize my right with my left.I had never tried twisting caps off like that and it worked perfectly. I am repairing a small DAT player, two actually, and this one is kicking my butt. They both had the same problem, one worse than the other. I've repaired five portable DAT units and 10 decks in the past year, just love tape.Jerry

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 17, 2024, 07:14:24 pm
content: I used to repair a lot of DAT's back in the day. Never liked doing the portable ones mind, good luck with that.One problem with them is the tape wrap is more than the 90 degrees you get in the larger format ones.It's a design bodge really, I used to refuse to repair them.Now I have no idea where you might get pinch rollers or mode switches for even the larger format DAT's.Is that a thing any more?

author: cncjerry
author_rank: Unknown
timestamp: November 17, 2024, 11:11:24 pm
content: Pinch rollers are no trouble, actually most parts you can order from Teac. For instance, I had been searching for the tascam drive belt that is cogged/ribbed/indexed depending on what you call them. Finally sent a note to teac parts and they had them. So most of the parts are available. People have ordered pinch rollers from them after I they sent me the belts.I wanted a TCD-D3 or a PCM-M1 to take on a long trip to Egypt & the Nile, so instead of ordering one that "worked" as they never do, I ordered two D3s and repaired them thinking I would get one but both worked after I oiled and unjammed the mecha. The first PCM-M1 I ordered works perfectly too. that's a cool device. I have two Tascam DA-P1 that work perfectly I had bought for the belts before I got them from teac. I don't think I paid more than $45 for either plus shipping but they are larger, pro boxes.Whenever I buy the TCD-D7s or D8s, they all fail. I owned one since it was released, say '90? and that broke a gear when the mecha jammed. I bought an iron gear I had to modify and won an auction (cheap) for another that has the exact same problem. I replaced the electrolytic caps but no joy, I need 6 more, none of the ones I need test fine in circuit. But they are strange caps. They have a rectangular case around an aluminum electrolytic with radial leads. 10uf @6v and 6.8uf at 6.3V and 10@4V. Can't even find the electrolytics in the needed values these days. Looked on Mouser and Digikey and they only have SMD. There isn't much room to put a higher voltage. I'm going to try eBay or just use tantalums for now as I have every value known to man.Even "excellent" TCD-D7 and D8's usually fail when you try to FF or RW to the next track (AMS). Same problem when you try to queue FF or RW. I check the RPMs of the drum, stare at the tape, everything looks perfect yet they sound like a tracking failure. I put them under a microscope and I can't see any variation in speed or tracking but it doesn't take much for the pinch roller to slip yet they have new rollers. The failure they have now is it seems like they are playing in LP mode, or maybe a head amp is failing.I love the confluence of hobbies (mechanics, electronics and audio). I've been a tapehead for a long time. I use an LTO library on my cloud even. I repair them for puzzles to keep me sharp.JerryI've repaired over 25 ADAT, DTRS and DAT decks as well as a PCM-F1 with two companion betamaxes in the past year alone. Of all those, the only I can't get working is this D7 but I have the schematics and waveforms, so I'll get it.

author: Audiorepair
author_rank: Frequent Contributor
timestamp: November 18, 2024, 12:53:32 pm
content: You really need the alignment tape to repair DATs.Sometimes they were massively out of alignment, one can only suppose the owner had had a go themseleves.