removing pcb mounted 3pdt

RnFR · Post by **RnFR** » 30 Mar 2009, 21:20

hey guys-

my buddy has a KOT with a bad pcb mounted 3PDT switch. i've removed the excess solder with braid, but am having a tough time getting it out. i really don't want to fuck up this pedal as it's not mine, so i'm kind of leery in handling it too hard. anyone have any suggestions for removing this stubborn bastard?
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oh yeah- i've got to have it done by tommorow!

RnFR · Post by **RnFR** » 31 Mar 2009, 02:42

bump?

madbean · Post by **madbean** » 31 Mar 2009, 03:17

Run a little solder over the lugs before hitting it with the braid. Pull the braid along between your iron and the lug when it starts to suck it up. This will soak up the solder more quickly. Do it in stages, though. Maybe 4-5 passes per lug. It will keep you from overheating the switch or burning up the board. You need to be careful not to pull too hard or at to strong of an angle. An angular push on a heated lug can push it through the sealer to one side.

I've used this method a number of times. It works!

RnFR · Post by **RnFR** » 31 Mar 2009, 04:50

great, thanks! i'll give it a shot.

i don't really give a deuce about the switch as i'm replacing it anyway, but the board is another story. i already gave it a bit of heat as it is, what kind of damage could happen to the board?

Ronsonic · Post by **Ronsonic** » 31 Mar 2009, 19:42

Madbean has the technique. I'm guessing these are tight through plated holes.

Once you think you've gotten the solder off, try flexing the switch body against the board and watch the pins. You'll be able to see if any are moving relative to their holes or not. That will tell you which need more work. Very often with a tight hole there will be some solder that won't wick out. You can use pliers to grab the lead of the switch and twist and rock it slightly to break that bit of solder. Do the rock and watch thing again. If you get down to one or two pins (even three if they're close to one another) that don't break free you can heat those while pulling the switch free.

The board damage to avoid - Excess heat can weaken traces and loosen them from the board material. It is also possible to remove almost all the solder from almost all the pins and have some on the top side of the board, under the switch that causes traces to tear off the board when you pull the switch off.

Alternate plans:

If you have access to hot air desoldering technology and this is a very good PCB, you can often heat an area of the board from below and blow hot air under the switch body and pull it off with pliers.

Lift off and nuke from orbit - it's the only way to be sure. Using a Dremel with cut off wheel, sharp flush cutter and other implements of destruction, destroy and cut away the body of the switch from above the contacts. You may have to remove other components to get access. I've had to do this with relays when solder had flowed onto the top of the pins on too many pads to heat and remove at once. One thing this approach does is show you what went wrong in your previous desoldering attempts. You'll see the solder built up on top of the board, etc.

JiM · Post by **JiM** » 31 Mar 2009, 21:11

If it's lead-free solder, you can lower the melting point by adding some non-RoHS SnPb solder.
Yes, it means adding some of what you want to remove, but it get easier. I mean, less difficult.

I once managed to desolder a relay who had everything against me : eight pins in tight plated holes, lead-free solder, thin copper but large ground plane on some pads ... it eventually went with both solder pump and braid, and not too hot a iron. I could then cut a trace below it, and put everything back without damage.

The most important thing was patience, let it cool down after heating a pin for a while and then attack another one. Like Ronsonic said, it also helped a lot to move/shake/wiggle a bit the relay while the solder cools down on one pin (even if it barely moves because of the other pins being solid), exactly what makes cold joints. If you can heat a full row at once, that's better. Eventually you'll get all pins loose but still stuck, then a repetitive mechanical action can free the part without much heat.

Good luck !

RnFR · Post by **RnFR** » 31 Mar 2009, 22:32

thanks for the tips guys! i'm going to try switching to a larger tip as well, and apply a decent amount of flux. hopefully i won't have to bust out the dremel!

i'll take another stab at it later after i get a bit of sleep.

RnFR · Post by **RnFR** » 01 Apr 2009, 11:37

well i finally got the thing out. unfortunately i took out a number of the plated holes with it. now that i fucked up the board does anyone have any suggestions? now the leds are working correctly, but there is no signal bypassed or otherwise. should i just try to fill the holes completely with solder in order to make the proper connections? maybe i should just call it a loss and have him take it to a pro.

ugh.

JiM · Post by **JiM** » 01 Apr 2009, 18:58

RnFR wrote:should i just try to fill the holes completely with solder in order to make the proper connections?

Either that or thin wrapping wire/inductor wire, soldered to the next pad on each trace.

RnFR wrote:maybe i should just call it a loss and have him take it to a pro. ugh.

D-I-Y POWAAAAAAAAAAAAAAAAAAAAAAAA

P1NkY · Post by **P1NkY** » 01 Apr 2009, 19:59

RnFR wrote:well i finally got the thing out. unfortunately i took out a number of the plated holes with it. now that i fucked up the board does anyone have any suggestions? now the leds are working correctly, but there is no signal bypassed or otherwise. should i just try to fill the holes completely with solder in order to make the proper connections? maybe i should just call it a loss and have him take it to a pro. ugh.

At one of my previous jobs - repairing damaged Kilowatt/Hour meters (RMA = ugh) they had these tiny eyelets, like the ones in your shoes where the laces go through. They came in various sizes, I think they were pre-tinned brass or something... Anyways, you'd pop one in the hole left by your lifted pad, crimp the other side using a small centerpunch (or small screwdriver, whatever you had handy) and solder the lifted trace to it. If the trace was too short, there were these self-sticking traces, or you'd jumper 'em with wire. The results were really good (after all, they had to pass a close scrutinization by the Q.C. peeps). I have no idea what they're called, if they're intended for that use or whatever, but I wish I would've held on to some...

So, like JiM said, DIY POWAAAAAAAAAAA.
Yep.

Edit: Shoulda Googled it first, they're expensive as cr*p - Check em out here: http://solder.net/PCB/default.asp
Ah, well...

RnFR · Post by **RnFR** » 02 Apr 2009, 18:23

P1NkY wrote:
RnFR wrote:well i finally got the thing out. unfortunately i took out a number of the plated holes with it. now that i fucked up the board does anyone have any suggestions? now the leds are working correctly, but there is no signal bypassed or otherwise. should i just try to fill the holes completely with solder in order to make the proper connections? maybe i should just call it a loss and have him take it to a pro. ugh.
At one of my previous jobs - repairing damaged Kilowatt/Hour meters (RMA = ugh) they had these tiny eyelets, like the ones in your shoes where the laces go through. They came in various sizes, I think they were pre-tinned brass or something... Anyways, you'd pop one in the hole left by your lifted pad, crimp the other side using a small centerpunch (or small screwdriver, whatever you had handy) and solder the lifted trace to it. If the trace was too short, there were these self-sticking traces, or you'd jumper 'em with wire. The results were really good (after all, they had to pass a close scrutinization by the Q.C. peeps). I have no idea what they're called, if they're intended for that use or whatever, but I wish I would've held on to some...

So, like JiM said, DIY POWAAAAAAAAAAA.
Yep.

Edit: Shoulda Googled it first, they're expensive as cr*p - Check em out here: http://solder.net/PCB/default.asp
Ah, well...

double ugh.

i'm going to try to fill the hole with solder and hopefully that'll do the trick.

Whoismarykelly · Post by **Whoismarykelly** » 02 Apr 2009, 18:55

This is probably irrelevant now, but did he try to send it back to analogman? They would have probably just dropped a new board in it and had a new one out to him in a day or two.

on topic - if you're going to sacrifice the switch anyway you could try disassembling the switch from the top side so you could just pull out each lug on its own? Too late for that though

lolbou · Post by **lolbou** » 02 Apr 2009, 19:00

Whoismarykelly wrote: on topic - if you're going to sacrifice the switch anyway you could try disassembling the switch from the top side so you could just pull out each lug on its own? Too late for that though

If the switch is out of order, then it seems like a very good idea to me (and I wouldn't have thought of it!)...

Whoismarykelly · Post by **Whoismarykelly** » 03 Apr 2009, 05:35

I got to thinking about this now and if I was designing a board with a PCB-mounted switch I would leave out the plated-through holes on the switch so repairs would be much easier.

soulsonic · Post by **soulsonic** » 03 Apr 2009, 08:10

Whoismarykelly wrote:I got to thinking about this now and if I was designing a board with a PCB-mounted switch I would leave out the plated-through holes on the switch so repairs would be much easier.

Well... I would use a footswitch that has proper PCB pins for mounting. Or, I would mount the board to the switch like how it is in a Rat with the wires running to it from the board; that's probably the most repair friendly I've dealt with so far.

Anyway, you can repair the board with thin wires just fine. I repaired an AD9 for a customer that had a board that was extremely cracked and broken all around where the power jack is, and I was able to get it back together and stay solid. You can strip out some stranded wire and use the individual strands for repairing thin tracks. Pretty much what JiM suggested. Since it's the holes that hold the lugs that are wrecked you could just follow the track back to its origin and run a small wire from there straight to the lug its track was going to... just ignore the damaged parts of the board and pretend you're building on perfboard.

RnFR · Post by **RnFR** » 03 Apr 2009, 09:34

soulsonic wrote:
Whoismarykelly wrote:I got to thinking about this now and if I was designing a board with a PCB-mounted switch I would leave out the plated-through holes on the switch so repairs would be much easier.
Well... I would use a footswitch that has proper PCB pins for mounting. Or, I would mount the board to the switch like how it is in a Rat with the wires running to it from the board; that's probably the most repair friendly I've dealt with so far.

Anyway, you can repair the board with thin wires just fine. I repaired an AD9 for a customer that had a board that was extremely cracked and broken all around where the power jack is, and I was able to get it back together and stay solid. You can strip out some stranded wire and use the individual strands for repairing thin tracks. Pretty much what JiM suggested. Since it's the holes that hold the lugs that are wrecked you could just follow the track back to its origin and run a small wire from there straight to the lug its track was going to... just ignore the damaged parts of the board and pretend you're building on perfboard.

thanks for the tip! i'll give this a shot!