21 Dec
2020
21 Dec
'20
4:11 p.m.
On 12/14/20 10:06 PM, Brent Hilpert via cctalk wrote:
On 2020-Dec-14, at 7:57 AM, Jules Richardson wrote:
Hey,
Just a heads-up, I finally got around to hooking it up - and it works just
fine on -5V. I'm not inclined to try -12V just in case it cooks, but I
suppose it's possible that it just needs some -ve voltage "more than x" and
so -12V is perfectly acceptable, too. Or maybe I just got lucky and this IC
is happy on -5V where some might not be.
I'm pretty happy that it's alive, anyway. I need to figure out what's going
on with the spacebar (it currently doesn't sit level), but time to figure
out some frankenproject for it!
cheers
Jules
On 12/14/20 4:41 AM, Brent Hilpert via cctalk
wrote:
...
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. (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)
I don't remember whether I traced it or measured it, but I'm fairy
confident, Vgg = -12 is pretty common for GI MOS ICs. I'll try to
remember to double-check it when I have the unit opened again.