Understood. (And for the record, I've checked my
wiring from the W076 a
dozen times. In fact, I just checked it again. I swear it's right.)
OK. About the only thing you could have got wrong is the polarity of the
wires in the current loop from itnerface to PDP8/L
Thanks for the explanation, Tony -- I appreciate it.
Based on this, and
what I'm currently seeing (i've double checked that the 8/L is
generating the current, and that the adapter is definitely not) it's
If you have wired the adpater as fig 2 i nthat doucment you pointed us
at, then it is passive.
looking like the adapter is at fault in some way. I
hope to have some
time this weekend to open it up and fool around with it as you've suggested.
I have looked at the PDP8/L maintenance manual on bitsavers. If the
scheamtic of the teletpye interface in Vol 1 is complete and accurate
(and I think it is), then it is clearly an active device and is actualyl
quite simple. I don't think the problem is there.
The docuemant on the RS232 adapter also incudes a schematic. I would work
through that. My first check would be on the LEd side of the optoisolator
in the PC->PDP8/L circuit -- that is the one where the LED is being
driven by the PC (RS232 interface). First check that the LED current
changes when you send breaks. If it doesn't you need to troubleshoot the
RS232 receiver, LED driver, etc. If it does, then you need to
troubleshoot the circuit on the transistor side of that optoisolator. It's
only a couple of transistors.
-tony