29 Aug
2006
29 Aug
'06
6:03 p.m.
Hello All. I'm new to this list and would like some advice on learning =
the inner workings of vintage computers. I have some basic experience =
with electronics and some simple measurement tools (multimeter, logic =
probe). So far, I've repaired a couple of older machines (Kaypro's, =
Compaq portables) but this has amounted to swapping dead hard or floppy =
drives, replacing dead batteries, etc. So here are my questions: (1) Is =
there a "trainer" system good for learning about microcomputer design =
There certainly _were_ Heathkit made at least one, so did (IIRC) HP. They
turn up on E-bay from time to time, but tend to go for what I consider to
be rather too much money.
What I would do in your position is get one of the simpler, but
well-known, 8 bit micros with few, if any, gate array chips (an Apple ][,
but not a //e, for example). And make sure a schematic is available.
Then, armed with test equipment, try to _really_ understand the design.
The first machine you do this for will take a long time. Later on you'll
be able to understand the schematic of a newly-obtained machine in a
couple of days.
Of course if you pick a machine that somebody else here knows about, you
can ask on the list questions like 'What the heck is NAND gate U24b for'.
and operation, and (2) would an oscilloscope be useful
for this purpose, =
and if so, what Mhz rating is needed to work on older machines? I've =
This is a personal thing. I don't use a 'scope much, prefering a logic
analyser, others prefer a 'scope.
But as I've said before, the most important piece of test equipment is a
brain. I've sorted out quite nasty logic faults using a multimeter, an
LED+resistor, and a lot of thought. But give the best logic analyser in
the world to somebody who doesn't know what they are doing, and it won't
help them at all.
To answer your second question, aim for a bandwidth ('MHz rating') of
about 3 times the fastest signal you want to look at (this may be the
master clock frequency). For most 8 bit micros, a 50MHz 'scope is fine.
And just as 'nobody ever got fired for buying IBM', you rarely go wrong
if you huy a Tektronix 'scope (no I don't work for them, I just like
their products).
-tony