On 12/14/20 4:41 AM, Brent Hilpert via cctalk wrote:
On 2020-Dec-14, at 1:26 AM, ben via cctalk wrote:
Often for data input one could use over strike characters for input. Not EQ
might be = BS | Did any video display terminals
repeat the same effect?
Yes. Coincidentally I've just been refurbishing one - a Teleray 3931.
It's an ASCII/APL terminal, overstriking was included for the APL mode.
http://madrona.ca/e/teleray3931/index.html
Holy cow, I have that keyboard. I picked it up as surplus a few years ago
from a place in Minneapolis and figured there was a very low probability of
ever figuring out what machine it originally came from.
I didn't know the necessary voltages for it - I mean, the grounds and +5V
are obvious, but I didn't know what it needed on pin 6. Given where I got
it from, there's probably a fair chance that it's faulty (and encoders
generally live a hard life), but I'll have to try powering it up now.
Just FYI if you're documenting things, mine has a very slightly different
PCB to accommodate a pair of tantalum caps on the inputs, rather than the
electrolytics on yours - caps are both rated 10uF, 35V. The encoder on mine
is the same p/n but in a black plastic package rather than white ceramic
(date code 7649). Sticker on the PCB underside says p/n 2129-009 and s/n
720 097.
(It's definitely -12V, not -5V? I'm just thinking that the -12V noted on
your schematic is quite close the the 15V rating on the cap - although that
could explain why my later setup got caps rated to 35V, too)
cheers!
Jules
