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Desoldering help

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First post, by AppleSauce

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I've recently started a project involving recapping an old abit bf6 motherboard.

I borrowed a proskit ss-331 desoldering gun from a friend and managed to get most of the caps out.

But there's a row that's being really stubborn and refuses to come out. I think there's still some solder in the through hole.

The guns temp is set to 370 degrees btw.

Anyone have any tips?

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Reply 1 of 28, by melbar

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I have re-capped several boards the last years.
After starting re-capping of the most critical capacitors on selected boards, during that time i have not bought a desolder gun,
i have used this multitool (dremel) to drill out the remaining solder at small holes. With this approach you have to take the smallest drill anyway.

Later i have bought a desolder gun additionally. For cases where you have bigger holes the gun is working really fine.
But for small holes i'm still working with my dremel.

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Reply 2 of 28, by Doornkaat

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Those capacitors are likely connected to two big copper planes. 370°C is not going to do the job with the relatively small thermal mass of a desoldering gun.
You can preheat the area with a hair dryer (reheat after each capacitor) and I would recommend you crank up the heat on the desoldering gun if preheating does not do the trick.

Reply 3 of 28, by konc

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My #1 tip: add new solder before attempting to desolder. Let the new solder mix with the old well. I can't stress this enough. And as weird as it sounds, repeat when needed. Yes, if the gun doesn't clear the hole solder it back with new solder and repeat. There is no point keeping the gun more time over the same spot trying to suck the solder and burning everything.

Tip #2: sometimes I find it easier to remove the capacitor (pulling GENLTY while heating) and then clear the hole from the remains. Again, work with both the soldering iron and the gun. Add a bit of solder to the hole to make a bump that the gun can melt without touching the board and then suck it to clear the hole.

Reply 4 of 28, by kaputnik

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Chipquik and equivalent Cerrolow 136 products can be very helpful when desoldering from multi layer PCBs with low power equipment. Instead of applying more heat, you lower the melting point.

Apply and keep heated a while to give it time to mix with the original solder. Remove with vacuum pump/solder braid/etc. Repeat if needed, until you can remove the cap.

Be sure to remove all residual solder/Chipquik before soldering in new caps.

Reply 5 of 28, by astonsmith

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konc wrote on 2022-04-02, 08:27:

My #1 tip: add new solder before attempting to desolder. Let the new solder mix with the old well. I can't stress this enough.

Of course, you mean new leaded solder... the first time I tried this, I was adding more and more lead-free to the mix and ultimately ruined the board. I didn't understand that leaded solder has a lower melting point, etc.

Reply 6 of 28, by AppleSauce

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Thanks for all the tips , I tried adding fresh leaded solder with mixed results , I ended up having to use the wiggle method to get some caps out.

I managed to pull it off but I never want to have to recap another multi layer pc motherboard again , it was a nightmare.

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Unfortunately the board is now covered with rosin cause I went a bit overboard and I cleaned off a fair bit but there's a fair amount left to do which I'm sure is going to be fun....

Also some of the through holes still have solder in them. Does anyone have a good method for opening them up?
(Like aside from drilling them , that sounds pretty risky to me 😒)

Edit: I just realised someone mentioned adding solder into the hole , I guess I could try that , I've seen some people mention using a toothpick to push it out online as well?
Anyone tried that?

Reply 7 of 28, by doogie

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For desoldering, I’ve had decent luck with this method: clamp the board so that it is held upright, then with one hand on the gun and the other on the cap, apply heat while applying pressure to the cap to get the leg you’re working on free of the board. The timing to hit the vacuum trigger was the trick to learn. After a few attempts I had it down. In the odd case where solder remains, I add leaded solder (I like Kester, fwiw), then heat the hole again with the gun.

I did splurge on a Hakko iron and desoldering gun - not the highest of the high end models, but I figure I won’t have to replace these things for a very long time.

Reply 8 of 28, by appiah4

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With ABIT boards, my advice for desoldering would be to just throw it away. Pieces of junk, really.

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Reply 10 of 28, by schmatzler

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appiah4 wrote on 2022-04-03, 18:06:

With ABIT boards, my advice for desoldering would be to just throw it away. Pieces of junk, really.

My VH6T is the best board I own, but to each their own, I guess.

I also had to recap that one, though. Got one of these Chinese "double pump desoldering guns" (S-998P) and it did the trick just fine. 🥰

Reply 11 of 28, by quicknick

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AppleSauce wrote on 2022-04-03, 14:29:

Also some of the through holes still have solder in them. Does anyone have a good method for opening them up?
(Like aside from drilling them , that sounds pretty risky to me 😒)

My method, used with 100% success so far:
Fill the stubborn holes with fresh solder, to create a small "dome" on each side.
Clamp the board so it sits vertically. I usually hold it between my knees 😁
Press the soldering iron (around 300 deg. C) on the left side, desoldering gun (around 380 deg.) on the right side. Solder melts extra-quick when heated on both sides.
Then it's a matter of synchronizing both hands - withdrawing the iron from the hole and immediately activate vacuum on the gun.

appiah4 wrote on 2022-04-03, 18:06:

With ABIT boards, my advice for desoldering would be to just throw it away. Pieces of junk, really.

Just throw them in my general direction, please 😁

Reply 12 of 28, by mattferris@hotmail.c

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appiah4 wrote on 2022-04-03, 18:06:

With ABIT boards, my advice for desoldering would be to just throw it away. Pieces of junk, really.

15yr old me gasps.

Thanks for the all the tips everyone. I've seen a few youtube videos on this topic. It looks like that kind of thing to practice on something you don't care about before you go prime-time on your favorite board.

Reply 13 of 28, by AppleSauce

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Thanks for all the suggestions ill try and use them to remove the solder now that I've cleaned the board up a bit.

I've got another question does anyone have a diagram for the values of the caps on the abit BF6s pcb , I made one but I want to cross check to make sure I got them right.

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Reply 14 of 28, by bofh.fromhell

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Seems correct.
Had a look at my unrestored version 1.1

1 = 4x = 1000uF, 6.3v, 8mm dia, 3.5mm lead spacing.
2 = 6x = 1000uF, 10v, 8mm dia, 3.5mm lead spacing.
3 = 11x = 1500uF, 6.3v, 8mm dia, 3.5mm lead spacing.
4 = 3x = 100uF, 16v, 6mm dia, 2mm lead spacing.
5 = 2x = 22uF, 16v, 4mm dia, 1.5mm lead spacing.

I don't think height is important in any of the positions.
Except maby the 2 closest to the CPU on the heatsink side, depending on the cooler you wanna use =)

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Reply 15 of 28, by bjrnx

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I did sometimes open the stubborn holes with a stainless steel needle of the right diameter - holding it with pliers and gently giving pressure to the blocked hole while heating up the needle with either hot air or a massive soldering iron (100 W classic style). And repetitive pre-heating the area with hot air as said before.

Reply 16 of 28, by AppleSauce

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Hokay jobs done , i'll need to double check it a bit more and might need to fix some solder joints , after that its gonna be time to test whether I fixed it or whether I killed it.

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Reply 19 of 28, by Cuttoon

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appiah4 wrote on 2022-04-03, 18:06:

With ABIT boards, my advice for desoldering would be to just throw it away. Pieces of junk, really.

🤣, I'm pretty sure with an average of five minutes of research, one can find that statement about any brand known to man.

I had a KT7-RAID and KR7A and was pretty happy with both. Clean layout, not stupid onboard sound, great bios.
True, they did not last forever but my gear tended not to once considered obsolete back then. (Think the latter was effed by a PSU failure, though.)

Oh, and Biostar really is shite, of course. 😜

I like jumpers.