Subject: Re: Desoldering a chopper transistor

[...] The advantage of no through plating is that its vairly easy to get all the solder off (it will not remain in the hole, holding the component lead to the sides of the hole). On the other hand, it's a lot easier to lift tracks on such a board. I think all the PCBs in a PDP11 are going to be through plated. It;'s been some time since I've worked on the PSU in question (H7140), but I am pretty sure the PCBs I repaired in mine were through plated. [...] Like you I've never got on with braid for desoldering through-hole parts. I have a reel in my toolikt though for some SMD repairs. It's useful for removign bridges between pins on SOICs and PQFPs. Actually, a lot of the ime, braid works well for desoldering such devices for removal. [...] That's fine for logic signal tracks, but for tracks carrying a higher current (for example inside the PSU), I'd use thicker wire. I am told taht for the highest reliability you should solder the wire to a component lead, via, or similar., and not just put it across the break and solder it to the track. That said, I have never found the latter method partciularly unreliable (by that I mean that I have repaired PCBs that way and nevre had problems from the repair going open-circuit). What does NOT work is to but a blob of colder across the break. I prefer turned-pin (machined pin) sockets. I don;t think I've evr had a bad contact in one of those. I;ll socket any 'expensive' or programemd device (EPROM, PAL, etc) that I've removed. But I generalyl solder TTL, 4000-series CMOS, etc, directly to the PCB. The on exception is on something that I am designing (where I socket everything), it's a lot easier to debug a circuit if you cna pull one of the ICs and inject suitble signals on the socket contacts. -tony