4 Feb
2004
4 Feb
'04
1:58 a.m.
Hi,
it must have been far too late this morning.
After a little sleep,
I found out what went wrong.
Both sides HP in the Reader Run Control an I in the
RSR232 -> 20 mA converter made assumptions on how
the other end handles the signals.
HP thinks TX+ (positiv wire of transmit) is permanently
tied to Vcc and TX- is floating (on signal).
And RX- (negativ wire of receive) is permanently tied to
GND with TX+ floating.
I did it the other way - tying TX- to GND and RX+ to Vcc.
So the reader run control could not work.
I now will rework my converter box and show the result
(if wanted).
Thanks to all who answered
Gerold
Gerold Pauler schrieb:
Hi,
in the process of restoring one of my teletypes I decided
to connect it to a PC. Send and receive work fine, but the
tape reader does NOT work in line mode (local is no problem).
It is an ASR33 relabeled by HP and has a HP Reader Run Control Card.
I have put a schematic of this card online
http://pdp8.de/download/HPtty.pdf
(Couldn't figure out the types of T1 and D1 - so these can be a pnp or
a zener diode also. Polarities of reader run signals (RDR+/RDR-) can
also be wrong.)
But I am too dump to understand how to connect the reader run signals.
I'm not even sure what levels they should have.
I just thought that a circuit identical to TX (on PC side aka RX on
teletype) should do.
If you need additional infos to help please let me know.
TIA
Gerold (pdp8.de)