Need Soldering Advice - removing switches - RESOLVED ?

[fohat.digs]

I am transplanting better switches into a Dell AT101 and I removed the black Alps from it.

Most of the legs were bent over, so I had to straighten them back upright. I did it with a small screwdriver, and was careful. Still, I was afraid I was damaging traces and solder mask.

Sure enough, when the new switches were in, 4 were dead. I carefully removed and re-soldered them, and one came back to life. However, the other 3 are fubar as far as I can tell.

Fortunately, I have at least one more AT101 to sacrifice, but I want to do it right this time.

I used a crappy solder sucker to get up as much of the original solder as possible, used a small flat head screwdriver with no sharp edges to gently bend the legs straight, and worked the switch out from the front, sometimes by hand, sometimes I had to use pliers (and it seemed uncomfortably like pulling teeth).

Is there anything else? I am going to try it again with even more care, but would love to hear any tips and tricks.

Thanks! Harry

[fohat.digs]

OK, 33 people have viewed this now, but no helpful hints?

Please, guys!

[Oobly]

Some advice: Only bend the legs straight when the solder is fluid. Otherwise it has a good chance of pulling up the pads. Also, keeping the heat on a pad too long can cause it to come loose from the board, but that's usually only in extreme cases.

In most cases, you can scrape the solder mask off a piece of the trace and flow the solder over that to make contact to the pin again. May be worth a try before moving on to the other board.

If you have a multimeter you can set it to check continuity and test the switches themselves and between the switch pins and PCB pads.

[Findecanor]

Also, keeping the heat on a pad too long can cause it to come loose from the board, but that's usually only in extreme cases.

I used to do that a lot when I first started to desolder switches. I used a 30W soldering iron, and some people have said that 30W is too much - it should only be 15W.
I am now using only my 15W iron and being more careful overall, and I don't have that much of a problem.

[fohat.digs]

Some advice: Only bend the legs straight when the solder is fluid. Otherwise it has a good chance of pulling up the pads. Also, keeping the heat on a pad too long can cause it to come loose from the board, but that's usually only in extreme cases.

In most cases, you can scrape the solder mask off a piece of the trace and flow the solder over that to make contact to the pin again. May be worth a try before moving on to the other board.

If you have a multimeter you can set it to check continuity and test the switches themselves and between the switch pins and PCB pads.

Thank you.

First, "when the solder is fluid" I suppose you mean to try to do it with the soldering iron tip itself?

Second, I tried flowing the solder back to a trace, but I think that I have lost both the pad and a few mm of trace.

Last, what do I test and/or look for when testing the switches themselves?

[Oobly]

Yup, use the iron tip or if you have enough hands free you can use the screwdriver while heating the solder with the iron.

You can use a small piece of wire to join a pin to a trace. Solder it to one side first so it kind of stays in place when soldering the other end.

Check that when you press the switch the pins become electrically connected. Then at least you know if the switch itself is working or not. If it is, then you know it's either the soldering to the board or some other thing wrong.

[MKULTRA]

Use a voltmeter to check the traces and make sure they are working properly.  Then you will know if you just need to bypass some traces.

[fohat.digs]

So, now I have a report.

I worked on the original circuit board for a while and got nowhere. I think that I really screwed up 3 connections. I have not thrown it into the garbage, and will buy some of the trace re-builder to try to fix it. I attempted to scrape away some solder mask and attach a very thin wire to that and the leg of the switch. It appeared to work when I soldered it, but the connection never "took" for some reason. Since they all work except 3, it will be shelved to my "project" list.

I dismantled another AT101W that was laying around (luckily, I had 3 that I would have sold, but you can hardly get over $15 + shipping on ebay, maybe $20 if you get lucky, and for that I would just as soon keep them) and started removing black Alps switches. Whoever built that board was much more zealous about bending the legs down, if the first one had been like that I would have wrecked a dozen switches instead of 3.

So, there were 4 pads that looked questionable, but they were only partially peeled up, not off altogether, so I was very cautious around them. I installed all my new switches, and only 2 did not work (both orange, luckily). I pulled them and tested them, one was OK and one was dead. So I replaced one and carefully put them back, and everything worked great!

Attached are photos of the project. The reason for the mix of orange and blue is that I had 88 blue switches (87 really, one was no good) and I wanted to be able to stretch them to populate 2 keyboards, at least for now.

I had 2 keyboards' full of orange switches, less a small handful that were no good, so I had all the "fillers" that I needed.

The best technique on the aggressively bent legs was to use a small flat screwdriver in one hand and the soldering iron in the other, and bend while the solder was soft. I used the solder sucker before and after this process, so the whole thing took a lot longer than the 2-step suck-and-pull I tried last time.

[AKIMbO]

More switches incoming!