In article ,
"N Cook" wrote:

N Cook wrote in message
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wrote in message
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I have an old project where a relay is oddly stuck in a state with the
common rail connected to the normally open contact. I can only assume
that the two connections fused together during a high-current
transient. The relay breaks a connection between an audio amplifier
circuit and a subwoofer. I think my only choice is to replace the
relay. There is however a problem where the pins of the relay are
soldered to plated through-holes. This is making the relay nearly
impossible to remove without risking damaging the pcb. Does anyone
have any neat tricks to remove such a component safely?
Thanks


Make up a pyramidal truncated frustrum (Google) out of 4 pieces of tin-
plate, wired together. Mask off that area around the relay, with the
frustrum temporarily wired to the board. Mount board firmly in vice, near
the relay. Pull and wriggle the relay when you apply heat from a hot-air
gun
directed into the frustrum.
If you don't believe it will work try the technique with plated thru comps
on a scrap board first. The hotter the air and quicker you are the better,
if board starts to discolour there is probably some other mechanical
restraint.


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/





As it happens, the last week I've been working on industrial boards with
plated-through soldering. Thick board so only tips of IC leads protrude,
very thin signal traces, traces to tiny pads on both sides of boards of same
pin in some cases and plated vias under ICs as well. I know if i'd used
"proper " vacuum assist desolder or butcher-and-remove single pins , many of
those traces/pads would have dislodged.
I had to sharpen the points of my large adapted circlip pliers to get the
extra purchase on the ends of these 14,16, and 28 pin ICs. Not one dislodged
track using a paint-strip hot-air gun. Next time i'll have to take some
before and after pics for the doubting thomases.

--

I'm not one of the doubting Thomases. Hot air works well. So do the
other methods, that you doubt. It's all about technique and finesse. The
professional desoldering stations work extremely well when used and
maintained properly, and virtually not at all otherwise. Blame the
operator.