12 May
2014
12 May
'14
11:26 p.m.
-----Original Message-----
From: cctalk-bounces at classiccmp.org [mailto:cctalk-bounces at classiccmp.org]
On Behalf Of Josh Dersch
Sent: 13 May 2014 07:03
To: General Discussion: On-Topic and Off-Topic Posts
Subject: DEC ASR-33 "reader run" debugging
Hi all --
Finally have the time (and space) to work on my PDP-8/L and its associated
ASR-33. The 8/L I've had running for a while now, but I've only recently
taken
the time to go over the ASR-33 it came with. It was a
bit dirty but it's
cleaned
up nicely and I've got it humming along nicely
now. (With the exception
of the
paper tape punch, which is going to need a bit more
work.)
At any rate -- this ASR-33 was outfitted with the DEC "reader run"
modification, and it does not appear to be functioning -- with the
teletype in
"Line" mode, the reader switch set to
"Start," and with the 8/L running
the RIM
loader the reader does nothing. (It also does nothing
when set to "Start"
in
"Local" mode, but I'm unsure if
that's expected or not...)
With the cover off, if I manually toggle the "trip coil" at the rear of
the unit the
reader runs and the 8/L receives data (and it looks to
be correct). I've
verified
continuity between the RELAY+ and RELAY- lines from
the W076 in the 8/L
all
the way to the reader run board, and I'm measuring
15V between the two.
It's about here where my naivete around analog electronics starts kicking
in
and I'm unsure where to go from this point -- any
suggestions are much
appreciated.
Thanks,
Josh
My suggestion is to join the Greenkeys list.
Regards
Rob