19 Dec
2009
19 Dec
'09
7:58 p.m.
Tony Duell wrote:
[Repairing a transistor]
This chip was soldered (on all 4
sides) in the middle of a fair size PCB
so I don't think I could have gotten to that spot with a file. It also
had several lifted pins with "blue-wires" going various places, and I
absolutely did not want to disturb any of those. The pin got broken off
in the first place while trying to blue-wire it. Some IC pin metal
seems to be quite brittle. Also, to be honest, I probably would not
have thought a file would cut through the encapsulation or be precise
enough in this case to expose just that one bit of metal. I can
visualize what you mean though; until I got a bit of a pit created it
was difficult to hold the bit in the right spot.
Heh! That's beautiful. In a late-night,
long-hours, weekend work
situation I did that once on one pin of a 386EX using a Dremel tool to
I've done that sort of thing to PROMs and PAls that have lost the odd
pin.
I normally use a hand file (as I did on the transistor in the Epson
printer), it seems more controllable to me.
To be honest I'd rather have replaced the transistor, but I can't find a
sensible source of 2SB705s. I think I found one dubious-looking website
A new CPU
would have been nice for us too, except for all the other
blue-wired pins. I was the "software" guy and I'm not sure what hot-air
soldering tools the other guy had access to either. I think there may
have been something out in the manufacturing area. I know there were
none in the engineering lab - typical mom and pop operation - I was
lucky to find a small cutter for the Dremel tool.
[1] Tower's International Transistor Selector. I
don't know if this
book
is known outside the UK, but it basically gives 1 line
of specs on just
about every transistor ever made. There's a similar one for FETs (JFETs
and MOSFETs( and one for Op-amps/Comaparators. And some others that are
less useful IMHO. But those 3 (and in particular the bipolar transsitor
one) ave very useful for anyone fixing old stuff.
I'm not familiar with that;
thanks for the tip.
-tony