24 Apr
2009
24 Apr
'09
11:36 a.m.
Tony Duell writes:
The most basic test is to remembner that a transistor has 2 diode
junctions, one between base and emitter, the other between base and
collector (no, you _can't_ make a transistor from 2 diodes!). So you
can test each of those junctions as a diode using either an analogue
ohmmeter, or more likely these days the diode-test range of a DMM.
Well, thanks, Tony. This is the first time I was confident I had
exactly the right info to help another list member diagnose a problem in
a couple of months, and you go and spoil it. Sheesh! (Just kidding...
I am not sure if you're being sarcastic or not, but I often do try to
point out the 'bleeding obvious' -- or at least what's obvious to me --
on the grounds that not everybody here is a hardware expert.
mostly.) Complicated questions on specific equipment
from companies
whose equipment I have not used makes trying to help out on this list
significantly more difficult.
I know the feeling. I always try to help with low-level hardware
problems, but it gets really difficult if I've not worked on the device
in question, if I don't have the service manual, etc.
FWIW, I almost always learn something from your posts, except in those
Thank you. I'd better keep on posting, then...
instances where your post confirms what I already
knew, and gets there
before I even read the question. You're quite an excellent resource for
the list, and I heartily approve of your approach, in terms of being
able to fix one's own equipment. That USED to be a necessary part of
I try to ensure that I don't depend on anything I can't fix. Period.
Which is probably why I have things like service manuals and ROM listings
for my pocket calculator.
[...]
interesting patterns on the LEDs.) Computer clubs
were places people
went to get soldering tips as much as discuss programming, despite
FWIW, there is still one club that's a bit like that. It's HPCC (Handheld
and Portable Computer Club). _Officially_ it's to exchange information on
HP calcualtors. But all sorts of things get discussed at the meetings,
things (old and new) get taken apart, machines (not just HP) get
repaired, or at least repairs suggested, programs get written, pulled
apart,... And so on.
Sorry for the digression. The point being that it
used to be MANDATORY
to be able to fix one's own computer, lest one become dependent upon the
Actually, I quite enjoy fixing things. Not so much the 'fix' as finding
out waht to fix. I like logical puzzles anyway, and tracking down an
obscure fault is a logical puzzle. Or at least it is if you do it the
traditional way of making measuremnets, thinking aout them, and only then
actually changing anything.
pity of others to get anything done. I find that
approach still useful
to some extent, and I've always been able to fix my own machines at
least as well as the (generally) trained-chimp-level techs at local
I am not sure that's very difficult :-)
fix-it shops. That many orders of magnitude of
complexity have come and
gone since the IMSAI days are good, in terms of what one's money will
buy today, but bad in that one is much less likely to be able to fix
one's own equipment to component level. It's not as satisfying to say
"Hmmm. You need a new video card" as to hold up the offending
transistor and cackle. Or is that just me?
This is, of cours,e the main reason that I still run classic computers
for somewhat serious work. There is a great feeling in knowing just what
has failed and being able to fix it.
-tony