OT? Apple Stylewriter problems (update)

From: Mark Tapley <mtapley_at_swri.edu>
Date: Fri Jan 18 10:09:31 2002

All,
        More info about the stylewriter.

1) Desoldered 4 of the 9 suspect transistors. They pass the 1-st order test
Tony suggested (high resistance E to C and C to E, current flows B to E and
B to C but not vice-versa). "Resistance" is not consistent if I change
ranges on my VOM, (I see the same needle movement on different ranges) but
is consistent among transistors and B-C to B-E. I busted two legs off while
trying to pull them out, so I'm definitely in the market for at least 2 and
up to 9 off 2SB1243 transistors (or equivalents). Anybody know a good
source near San Antonio?

2) The markings were indeed "B1243". The only other markings are a pair of
digits that look like "88" under the "43", but the first "8" has too big a
top loop and too little a bottom loop, and both are slightly squared-off
compared to a normal "8".

3) All the transistor Collectors go to wide traces on the ribbon cable via
two pins each on the connector.

4) All the Emitters are ganged together via a wide trace on the PCB. I have
not figured out where that trace ends up. Emitters also have narrow traces
leading into a big array of small surface-mount components with numbers
like "511" or "151" on them (not necessarily those numbers, but numbers
like those).

5) The bases also have narrow traces going off into the small surface-mount
array.

6) The power supply wall-wart does not have any fasteners under the label,
nor any feet. Its recessed fasteners have hemispherical metal heads covered
with some sort of dark anodize-like coating (it can be scratched off with a
sharp tool).

        Next project is to pry the seam apart on the power supply, shove in
a screwdriver to hold it open thereby putting some tension on the
fasteners, then take a soldering iron to the fasteners to heat them up and
see what gives. I'll try to do some more circuit-tracing as well, but that
is looking harder.
        I'll also check the ribbon cable again. I put that off until I ran
out of time last night, in part because I'm gonna feel really goofy if that
turns out to be the problem after all.
        BTW, my VOM runs on a single AA 1.5V battery. Can I toast anything
by trying to check resistance with it? Should I stay out of the "R x 1"
range or something like that?
                                                                - Mark
Received on Fri Jan 18 2002 - 10:09:31 GMT