Desoldering a chopper transistor

On 7 May 2011 at 10:04, Rob Jarratt wrote: If you're going to do much repair of PCBs, a temperature-controlled iron is pretty important. I use my venerable Weller TCP iron--a time- proven design that's still in production after, what, a half-century? However, there are less-expensive imported options. A clean and well-tinned iron is vital to this kind of work. If your iron isn't tinned, the molten solder can't conduct heat to the joint and you end up spending too much time trying to get a joint to melt. If you're using a solder pump, make sure it's the big one; the little ones don't seem to be worth much. It often helps to add solder to a joint before you use the pump to suck the solder out. Once you've sucked the solder out of a joint (you should be able to see daylight through the joint), wiggle the component gently to break the bond between the lead and the PCB trace formed by any remaining solder film and it should pop right out. Others have suggested cutting the component body off the leads to reduce heat conduction away from the joint being worked on--and that's a very good suggestion. If you still don't trust yourself, you may want to look into a low- temperature solution, such as Chip-Quick, which is basically a low- temperature fusible alloy that takes solder into solution. It's quite valuable duing SMT rework (I have yet to damage a PCB using it to replace surface mount ICs), but it might also work with traditional through-hole devices. http://www.chipquikinc.com/index.htm I've got lots of desoldering braid, but I tend to use it for soldering SMT packages, rather than desoldering them. --Chuck