Originally Posted by lordearl
The other option is of course to simply cut the traces on the PCB which are leading to where I've incorrectly soldered the BD137, then solder a jumper on the underside of the board to where the BD137 should have been soldered in the first instance.
That is probably the easiest solution as I won't be using any other transistors besides the BD137/BD138, the desoldering is simply too perilous!
I would strongly recommend against this:
1. Traces are not all that easy to cut - you'd have eight of them to do. The board will end up pretty messed up by the time you get through with it. It might not even be usable.
2. To make matters worse, you have to engineer a crossover. You can't simply solder some spent leads in a different direction - they have to cross over one another.
The simplest answer is to remove the transistors. You only need to make a blob of melted solder big enough to cover all three pins. A lot of the time, the transistor will simply drop out of the board. If not, you can tie a string or something similar through the mounting tab hole. Pull on the string when you have the solder blob melted and it will come right out.
You don't absolutely need the heat sink mounting pads in a case like this. Yes, it's nice to start with them, but you could simply smear some Vaseline on the backs of the transistors and probably get 90% of the heat transfer effect. For that matter, since the transistors are all plastic-bodied, you could mount them dry and get probably 75% of the heat transfer effect. The differences may be even closer than that - I'm just guessing.
Anyway - cutting traces on a PCB is the absolute last resort. Never do it if you can help it.
Edit: Changed a word that might be interpreted as vulgar by our international folk.
Edited by tomb - 9/13/13 at 6:05am