28 Mar
2005
28 Mar
'05
1:55 p.m.
At the Northrop-Grumman (nee TRW) swap meet yesterday
I bought what appears to be an 8-bit ISA bubble memory card.
It's labeled as a circuit lab UL-82094.
I've got photos of the board at
http://decodesystems.com/help-wanted/bubble-memory-board.html
Does anyone have any documentation and/or drivers for this board?
Documentation on the bubble chip set is at
http://oldcomputers.dyndns.org/public/pub/rechner/epson/~fjkraan/comp/pc500…
Cheers,
Dan
Fred Jan
28 Mar
28 Mar
2:14 p.m.
New subject: DEC PC04 Paper Tape Reader/Punch
Hi, All,
I've got a DEC PC04 punched tape reader/punch that I've been working
on getting running on my PDP 8/e.
The punch seems to work well.
The reader, on the other hand, has a problem. The 2^2 bit is always stuck
low. So, I started tracing things down, and found that the phototransistor
in the read head at that bit position is 'dead'.
Problem is, the reader uses an array of 10 phototransistors, (8 for data
holes,
one for sprocket hole detection, and the last for detecting an "out of tape"
condition)
arranged in a linear array with 0.10 spacing, with built in lens bubbles.
There's no way to substitute just the one failed phototransistor.
I can't find anyone online that has anything similar to this array
avaialble.
I'm hoping someone out there has experienced a similar situation, and may
have
some ideas as to how I can get the reader working 100% again. I want to run
all
of the MAINDEC diagnostic tapes on the CPU, but it's tough without the
reader.
Thanks,
Rick Bensene
The Old Calculator Web Museum
http://oldcalculatormuseum.com
2:46 p.m.
New subject: DEC PC04 Paper Tape Reader/Punch
Rick, see if you can track down the schematics and verify that it's
actually the photo-transistor element that's dead. It could
merely be a loose wire, or a bad component in the buffer/amplifier
comparator/filters in each of the channels. The surest way to be sure
would be to put a scope right on the lead of the sensor array's output.
Typically phototransistor would be pulled up to +V supply by a resistor
and optionally biased by another resistor on the base. Check those two
resistors and the make sure nothing is shorting the collector's output -
then
trace that bit back all the way to the interface buffer to the omnibus.
good luck! -h
Rick Bensene wrote:
I've got a DEC PC04 punched tape reader/punch that
I've been working
on getting running on my PDP 8/e.
The punch seems to work well.
The reader, on the other hand, has a problem. The 2^2 bit is always stuck
low. So, I started tracing things down, and found that the
phototransistor
in the read head at that bit position is
'dead'.
Problem is, the reader uses an array of 10 phototransistors, (8 for data
holes,
one for sprocket hole detection, and the last for detecting an "out of
tape"
condition)
arranged in a linear array with 0.10 spacing, with built in lens bubbles.
There's no way to substitute just the one failed phototransistor.
3:12 p.m.
New subject: DEC PC04 Paper Tape Reader/Punch
I have verified that the phototransistor element itself is dead.
Everything else through the interface to the Omnibus is fine.
I've even swapped the wiring at the phototransistor array so
that a different channel of the amplifier board was hooked up
to the phototransistor, and it was still dead.
It seems odd that a phototransistor would fail, but it's pretty
clear at this point that it is, which puts me in the bind of trying
to find another phototransistor array.
Thanks for the help, though.
-Rick
-----Original Message-----
From: cctalk-bounces at classiccmp.org
[mailto:cctalk-bounces at classiccmp.org] On Behalf Of Heinz Wolter
Sent: Monday, March 28, 2005 11:47 AM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Re: DEC PC04 Paper Tape Reader/Punch
Rick, see if you can track down the schematics and verify
that it's actually the photo-transistor element that's dead.
It could merely be a loose wire, or a bad component in the
buffer/amplifier comparator/filters in each of the channels.
The surest way to be sure would be to put a scope right on
the lead of the sensor array's output.
Typically phototransistor would be pulled up to +V supply by
a resistor and optionally biased by another resistor on the
base. Check those two resistors and the make sure nothing is
shorting the collector's output - then trace that bit back
all the way to the interface buffer to the omnibus.
good luck! -h
Rick Bensene wrote:
I've got a DEC PC04 punched tape reader/punch
that I've
been working
on getting running on my PDP 8/e.
The punch seems to work well.
The reader, on the other hand, has a problem. The 2^2 bit
is always
stuck low. So, I started tracing things down,
and found that the
phototransistor
in the read head at that bit position is
'dead'.
Problem is, the reader uses an array of 10 phototransistors, (8 for
data holes, one for sprocket hole detection, and the last for
detecting an "out of
tape"
condition)
arranged in a linear array with 0.10 spacing, with built in
lens bubbles.
There's no way to substitute just the one
failed phototransistor.
7021
days inactive
7021
days old
3 comments
3 participants
participants (3)
-
fjkraan＠xs4all.nl -
h.wolter＠sympatico.ca -
rickb＠bensene.com