Desoldering a chopper transistor

On 07/05/2011 10:04, Rob Jarratt wrote: You don't normally desolder more than one pin at a time but you do need a good iron and a good pump. On DEC PSUs particularly, I've found the holes are, um, less than generous -- the component pins tend to be a close fit and there's not much room around the pin even when you get all the solder out. I normally use a 100W Weller soldering gun for things like those trannies (I have a 50W Weller temperature-controlled iron for anything else). The trick is to get the solder hot enough to flow, and to do so quickly. If you can't do that, you're unlike to succeed, and the longer you leave the heat on the pad, the more likely you are to damage something. Then use a large pump to suck it off. Sometimes adding fresh solder and trying a second time helps -- the first attempt removes most of the oxidised stuff and the flux from the fresh solder helps remove the last of it. Then push the pin from side to side to break the last whisker of solder that bridges from the pad across the gap to the pin -- if you can! I'd suggest getting a bigger iron if you can, and don't use a narrow tip for large components. I wouldn't waste any time on solder braid, either -- fine for small stuff but probably not for this. -- Pete Peter Turnbull Network Manager University of York