Well, I replaced the broken diode with a 1n4004 -
looking at the circuit, I see no reason why it
wouldn't work, it's just serving as a rectifier. No
change in the operation of the teletype, it still
doesn't run open/rattle like it's supposed to. I did
some poking around and found that the device at CR5
was shorted. According to the teletype manual, CR5 is
a 100A varistor. Now, how I managed to blow that up
with a 12v DC plugpack is beyond me if it's rated for
100A, but still, it was shorted. Removing it from the
circuit restores the normal operation. It rattles in
line mode, and works like a typewriter/tape punch in
local mode. Touching the RX lines together in line
mode makes it stop rattling, and tapping them together
can make it print assorted characters.
So, I need to replace that varistor - it evidently was
there for a reason, and it kept me from blowing up the
transistor (no idea where I'd find a replacement for
that...) Anyone know a replacement? The only varistors
I am familiar with are those flat disc types that are
used in power strips as "surge protection".
-Ian