Saturday, 12 September 2009

Getting a quick fix

OK, that wasn't too bad. After perusing various websites to learn how best to deal with my little cooking problems from last night, I set up my soldering iron with its finest tip, and had my solder wire and desoldering braid (and tweezers this time, after discovering I was burning my hand last time I used the braid) to hand. My iron tip is actually finer at the very end than the tweezers.

I started off trying to use the braid to deal with those solder bridges on the chip, but just couldn't get the braid hot enough to melt and draw out the solder in the gaps between the legs. After trying several times, I simply used the iron tip to heat the bridging solder directly, then quickly drew the tip down, bringing the solder with it. This spread the solder onto the legs either side, and I did this for all the bridged legs until I soon had no more bridging.

Here is a picture of the legs on one side of the chip:

and here is the other side:

OK, it's not exactly pretty, but it should work.

Next I used the iron to melt the solder at one end of the cracked capacitor, and used tweezers at the same time to encourage separation. I only moved it a bit whilst the solder was molten. I repeated this at the other end, and went back and forth a couple of times until the capacitor was freed.
While there was free access, I used my Stanley knife blade on its non-blade edge to remove the problematic solder balls, and cleared the others off the board, too.

I put a new capacitor in place, and using my fine soldering iron tip, still, with 0.7 mm solder wire, I was able to solder it in place, although positioning it whilst soldering was awkward. I used a tiny blob of Blu-Tak on the end of the tweezers to try to stop it sliding around. You can see it here (it is capacitor C1 just in front of the chip) and isn't straight, but it has made contact. There is too much solder there, too. Tough!

I used the soldering iron to try to melt the solder under the centre electrolytic capacitor, trying hard not to put too much heat onto the neighbouring (and very close) chip, but mostly melted the black plastic base of the capacitor, so I can't see if the solder has melted!

So here is the fixed? board:

Only, I think there is another problem - the electrolytic capacitor on the edge. The capacitor isn't aligned with its board-diagram. There is contact on one side:

but on the other the lead on the capacitor is visible, but the pad isn't, and I don't know if contact has been made. You can just see the lead obscuring the C6 marking:

Now how do I check the electrolytic capacitors for contact?

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