[GreenKeys] Curious Model 15/19 problem

[Joe Duszyński]

Here is an odd problem with a Model 15/19 with Keyboard perforator.
With the switch set to "Keyboard"
The machine works fine, types fine, punches tape fine, there is also a
typing reperforator on the loop it prints fine and the computer reads the
loop ZERO PROBLEMS along with another teletype on the loop no issues in
this mode.

With the switch set to "Tape" it punches fine. ZERO PROBLEMS the switch in
this mode does not transmit from the keyboard its tape only.

Now the problem occurs when it's set to "Keyboard & Tape" The keyboard
punch punches the correct code to the tape, but the printer drops the
second bit and types T instead of L, M instead of V, <CR> instead of R.
Slow typing RYRYRY gives <CR>Y<CR>Y<CR>Y on the printer.
Fast typing RYRYRY gives RYRYRY and occasionally it will <CR>instead of R
The Reperforator, Computer and anything else on the loop receives the
correct L V R RY whatever with no glitches. Looking at the loop with a
scope I don't see any issues no spikes or drops and the scope will display
the correct bit pattern for the typed character.
The loop current is 60ma right on the money.
The keyboard is obviously sending the correct code as the Reperf,Computer
and other teletype receive ok and the tape punch is a mechanical linkage
and it punches the correct code on the tape......
Still in the "Keyboard & Tape" position If I transmit a tape that printer
works fine If I send copy from the other teletype or the computer it also
works fine.
The issue only occurs with the switch in "Keyboard Tape" and slow hunt an
peck typing on the local keyboard and the local printer.
Flip the switch to "Keyboard" and you can hunt and peck type and the
printer prints fine, switch it back to "Keyboard Tape" do the same thing it
drops

I'm kinda of the opinion that it may be the solenoid/magnet that operates
the punch but I don't see it causing any sort of spike or drop on the
oscilloscope that would cause any interference and everything else on the
gets the code ok.
Sort of gave up for the night as I'm at wits end "I'd pull my hair out but
I'm already bald" LOL! Tomorrow I might cut the wire to the punch
solenoid/magnet
and see if that does anything.
If anybodys come across this before I'd love to hear how ya solved it!!
JD.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/greenkeys/attachments/20211116/28ee7a9f/attachment.html>