Adventures in Metallurgy

By kind donation we have an additional dead Electron board in our collection, so Ed decided to start getting some desoldering experience on a couple of scrap boards. At the very least, we'll need to desolder the 40-pin CPU, and perhaps it will also be useful to desolder the 68-pin ULA.

We tooled up with some Field's Metal and a cheap and cheerful butane powered blowtorch - something which melts at domestic temperatures and something to supply more heat than we should sensibly apply to a circuit board. This is sure to be a success!

Field's Metal will melt in hot water, so we only had to wave a hot iron at the pictured lump to collect a few big drips in a foil tray.

One desoldering approach is to replace the solder with the alloy, remove the alloy with a desoldering pump, and then apply mild heat to the board. Any remaining alloy will melt and the part can be removed.

Well, certainly the part was removed. Only a little of the alloy escaped to the food preparation area. Only one cooking utensil was tagged with a "Not for food use" label by the kitchen police.

The alloy approach having worked once, on a 30-pin SIMM socket, Ed had a try with the blowtorch on a 40-pin DIL socket. Near the socket anyway: let's just say that damage was done. Next time, perhaps a lighter touch on heating everything gently and evenly.

So, back to the alloy, but using the torch with the soldering tip. Still too hot! When the 40-pin socket eventually became free, it only had 35 pins left.

Time for a tactical withdrawal! Next time, listening to advice, we'll be preheating, re-soldering and taking more care with the desoldering pump. For the CPU, we'll try heating from the component side as we desolder from the underside.

(We're still chasing down a logic problem in the accelerator card: we're going to fit up one of our FPGA modules as a logic analyser.)