16 May
2024
16 May
'24
2:13 p.m.
I have a Decitek 442A9 papertape reader which needs repair.
I have already replaced the belt, but that is not enough. The reader behaves very
strangely. It
starts running as soon as I apply power. And there is another problem: when I load a tape,
it
rattles irregular during reading. This is not a mechanical problem, it seems to react to
the pulse
of the feed hole, which arrives at the wrong time.
I'm pretty sure, that I have to adjust the sprockets somehow relative to the stop
positions of the
stepper motor.
It was nothing to be found online except pictures of a similar model 443A9 at RICM:
https://www.ricomputermuseum.org/collections-gallery/equipment/dec-pdp-8s-4.
The controller board number is 30291A
Does anyone happen to have the manual and/or schematics or any other documents?
Thank you,
Micha
16 May
16 May
3:06 p.m.
Decitek is still in business, so try decitek.com
On May 16, 2024, at 10:13 AM, Michael Fritsch via
cctalk <cctalk(a)classiccmp.org> wrote:
I have a Decitek 442A9 papertape reader which needs repair.
I have already replaced the belt, but that is not enough. The reader behaves very
strangely. It starts running as soon as I apply power. And there is another problem: when
I load a tape, it rattles irregular during reading. This is not a mechanical problem, it
seems to react to the pulse of the feed hole, which arrives at the wrong time.
I'm pretty sure, that I have to adjust the sprockets somehow relative to the stop
positions of the stepper motor.
It was nothing to be found online except pictures of a similar model 443A9 at RICM:
https://www.ricomputermuseum.org/collections-gallery/equipment/dec-pdp-8s-4.
The controller board number is 30291A
Does anyone happen to have the manual and/or schematics or any other documents?
Thank you,
Micha
3:22 p.m.
It looks as though Decitek remain in business http://www.decitek.com/index.html
Scan of a series 700 reader manual on bitsavers http://www.bitsavers.org/pdf/decitek/
On an optical reader, I would not recon the capstan running at power on as unusual - a
pinch roller which engages for drive and a tape clamp engaging for stop motion are both
common features. For simple single byte read operations, probably the paradigm used when
the unit was built, it is not uncommon for the sprocket hole to stop feed and energise
clamp. The circuitry to control this behaviour may be in the drive or controller or
shared; and then there are configuration links / switches ...
An empirical approach is to scope / LA the sprocket and data bit outputs; ideally with a
tape loop.
HtH; Martin
-----Original Message-----
From: Michael Fritsch via cctalk [mailto:cctalk@classiccmp.org]
Sent: 16 May 2024 15:14
To: General Discussion: On-Topic and Off-Topic Posts <cctalk(a)classiccmp.org>
Cc: Michael Fritsch <mi(a)fritscholyt.de>
Subject: [cctalk] Papertape-Reader Decitek 442A9: need manual/schematics
I have a Decitek 442A9 papertape reader which needs repair.
I have already replaced the belt, but that is not enough. The reader behaves very
strangely. It starts running as soon as I apply power. And there is another problem: when
I load a tape, it rattles irregular during reading. This is not a mechanical problem, it
seems to react to the pulse of the feed hole, which arrives at the wrong time.
I'm pretty sure, that I have to adjust the sprockets somehow relative to the stop
positions of the stepper motor.
It was nothing to be found online except pictures of a similar model 443A9 at RICM:
https://www.ricomputermuseum.org/collections-gallery/equipment/dec-pdp-8s-4.
The controller board number is 30291A
Does anyone happen to have the manual and/or schematics or any other documents?
Thank you,
Micha
4:02 p.m.
I know the document on bitsavers, but the series 700 is a complete different one.
In this reader there is no clamp or breake or similar things, but a stepper motor which
drives two
sprocket wheels. Between the wheels is the optical sensor.
In the moment I'm about to reverse engineer the board. The db25 connector at the back
is almost
completely populated. I would like to known what the pin are for. Very good, that Decitek
still
exists. I will write them.
Micha
Martin Bishop via cctalk wrote:
It looks as though Decitek remain in business
http://www.decitek.com/index.html
Scan of a series 700 reader manual on bitsavers http://www.bitsavers.org/pdf/decitek/
On an optical reader, I would not recon the capstan running at power on as unusual - a
pinch roller which engages for drive and a tape clamp engaging for stop motion are both
common features. For simple single byte read operations, probably the paradigm used when
the unit was built, it is not uncommon for the sprocket hole to stop feed and energise
clamp. The circuitry to control this behaviour may be in the drive or controller or
shared; and then there are configuration links / switches ...
An empirical approach is to scope / LA the sprocket and data bit outputs; ideally with a
tape loop.
HtH; Martin
8:15 p.m.
Micha
That the board is TTL and 2 layer by the look of it makes reverse engineering rather more
tractable : good luck.
The 25p D pin outs for readers/punches seem substantially standardised, I think you will
find that the Dostek 440 manual (which is a solid state substitute for PTP / PTR) will
get you a long way. The use case for PT after the early 70's seems to have primarily
been CNC, feeding G code to machines.
Additionally, the DEC PC-04/05 and PC-11 manuals / eng drws should provide a worked
example from the same era (they are online). They look to be sprocket fed, and have (eg)
details of motor / sprocket adjustment.
You will also find Facit N4000 and 4070 documentation on line; however, 232 interfaces
seem to be the prefered flavor
GNT is another PTR/PTP OEM, again with some documentation online, model numbers include
36, 4601, 4604, 3406, 29
I have a Sanyo Denshi 2702 PTR (sprocket feed) which is on the gather dust manyana list.
I have a serviceable friction feed / optical sense reader which I much prefer, the
sprockets look to me like a paper shredding mechanism.
HtH Martin
-----Original Message-----
From: Michael Fritsch via cctalk [mailto:cctalk@classiccmp.org]
Sent: 16 May 2024 17:02
To: cctalk(a)classiccmp.org
Cc: Michael Fritsch <mi(a)fritscholyt.de>
Subject: [cctalk] Re: Papertape-Reader Decitek 442A9: need manual/schematics
I know the document on bitsavers, but the series 700 is a complete different one.
In this reader there is no clamp or breake or similar things, but a stepper motor which
drives two sprocket wheels. Between the wheels is the optical sensor.
In the moment I'm about to reverse engineer the board. The db25 connector at the back
is almost completely populated. I would like to known what the pin are for. Very good,
that Decitek still exists. I will write them.
Micha
Martin Bishop via cctalk wrote:
It looks as though Decitek remain in business
http://www.decitek.com/index.html
Scan of a series 700 reader manual on bitsavers
http://www.bitsavers.org/pdf/decitek/
On an optical reader, I would not recon the capstan running at power on as unusual - a
pinch roller which engages for drive and a tape clamp engaging for stop motion are both
common features. For simple single byte read operations, probably the paradigm used when
the unit was built, it is not uncommon for the sprocket hole to stop feed and energise
clamp. The circuitry to control this behaviour may be in the drive or controller or
shared; and then there are configuration links / switches ...
An empirical approach is to scope / LA the sprocket and data bit outputs; ideally with a
tape loop.
HtH; Martin
9:20 p.m.
On 5/16/24 15:15, Martin Bishop via cctalk wrote:
Micha
That the board is TTL and 2 layer by the look of it makes reverse engineering rather more
tractable : good luck.
The 25p D pin outs for readers/punches seem substantially standardised,
I believe the standard is RS-323 (all search attempts assume
you mean RS-232). The logic levels are 12 V or so, so not
quite TTL compatible.
Jon
9:46 p.m.
The D-25 PTR / PTP parallel interfaces are TTL, the ones I have had on the bench at any
rate, typically using 74 series for interfacing and 5V rails. Generally, the data lines
are on pins 1 to 8 after that it gets a bit YMMV and at the top end you get ground and
exported voltage. Hence my Dostek's emulator is a good guide comment. Additionally,
the pin out does not mimic what must be the later D-25 PC printer plug layout.
An additional confounding factor is that PTR/PTP are substantially from the era when D-25
connectors were commonly used for RS232 serial comms, and quite a few featured serial
interfaces : RTFM territory.
+/- 12V levels were used for RS232 back in the day, these days a MAX3232 on 3v3/LVTTL with
integral charge pumps for +/- 6v is typical.
And of course RS-423, RS-422 and RS-485 are all potentially applicable interface circuit
standards; however only RS-485 is not in the legacy category
Numeric gloup
Martin
-----Original Message-----
From: Jon Elson via cctalk [mailto:cctalk@classiccmp.org]
Sent: 16 May 2024 22:20
To: Martin Bishop via cctalk <cctalk(a)classiccmp.org>
Cc: Jon Elson <elson(a)pico-systems.com>
Subject: [cctalk] Re: Papertape-Reader Decitek 442A9: need manual/schematics
On 5/16/24 15:15, Martin Bishop via cctalk wrote:
Micha
That the board is TTL and 2 layer by the look of it makes reverse engineering rather more
tractable : good luck.
The 25p D pin outs for readers/punches seem substantially
standardised,
I believe the standard is RS-323 (all search attempts assume you mean RS-232). The logic
levels are 12 V or so, so not quite TTL compatible.
Jon
5:26 p.m.
On May 16, 2024, at 11:22 AM, Martin Bishop via cctalk
<cctalk(a)classiccmp.org> wrote:
It looks as though Decitek remain in business http://www.decitek.com/index.html
Scan of a series 700 reader manual on bitsavers http://www.bitsavers.org/pdf/decitek/
On an optical reader, I would not recon the capstan running at power on as unusual - a
pinch roller which engages for drive and a tape clamp engaging for stop motion are both
common features. For simple single byte read operations, probably the paradigm used when
the unit was built, it is not uncommon for the sprocket hole to stop feed and energise
clamp.
There are two basic design schemes for optical tape readers: a sprocket wheel that engages
the tape and does the start-stop motion, typically with a stepper motor; and a transport
roller with pinch roller and brake, typically solenoid driven. The DEC PC11 is an
exaxmple of the former. The latter are more likely to show up in high speed readers
because the tape motion is continuous, so easier on the tape as long as it doesn't
need to stop.
I'm still amazed at the Electrologica X8 tape reader, rated at over 1000 characters
per second, and able to stop and restart without skipping a byte.
paul
5:21 p.m.
I have something close-ish
http://www.memex.ca/wp-content/uploads/old/M110545-Dostek-440A-BTR-User-Gui…
Bill
On Thu, May 16, 2024, 10:33 AM Michael Fritsch via cctalk <
cctalk(a)classiccmp.org> wrote:
I have a Decitek 442A9 papertape reader which needs
repair.
I have already replaced the belt, but that is not enough. The reader
behaves very strangely. It
starts running as soon as I apply power. And there is another problem:
when I load a tape, it
rattles irregular during reading. This is not a mechanical problem, it
seems to react to the pulse
of the feed hole, which arrives at the wrong time.
I'm pretty sure, that I have to adjust the sprockets somehow relative to
the stop positions of the
stepper motor.
It was nothing to be found online except pictures of a similar model 443A9
at RICM:
https://www.ricomputermuseum.org/collections-gallery/equipment/dec-pdp-8s-4
.
The controller board number is 30291A
Does anyone happen to have the manual and/or schematics or any other
documents?
Thank you,
Micha
6:33 p.m.
Thank you Bill, but the board in the link is completely different.
The board in my reader is almost identical to the one in this auction (version D vs. A):
https://www.ebay.co.uk/itm/333131813919
Only TTL-Logic, no processor, no UART, paralleöl data output.
Micha
Bill Degnan via cctalk wrote:
I have something close-ish
http://www.memex.ca/wp-content/uploads/old/M110545-Dostek-440A-BTR-User-Gui…
Bill
7:28 p.m.
It would have been quite a bit of good luck, but I thought maybe ....
b
On Thu, May 16, 2024 at 2:53 PM Michael Fritsch via cctalk <
cctalk(a)classiccmp.org> wrote:
Thank you Bill, but the board in the link is
completely different.
The board in my reader is almost identical to the one in this auction
(version D vs. A):
https://www.ebay.co.uk/itm/333131813919
Only TTL-Logic, no processor, no UART, paralleöl data output.
Micha
Bill Degnan via cctalk wrote:
I have something close-ish
http://www.memex.ca/wp-content/uploads/old/M110545-Dostek-440A-BTR-User-Gui…
Bill
191
days inactive
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days old
10 comments
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participants (6)
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Martin Bishop -
Michael Fritsch -
Michael Thompson -
Paul Koning