Paper Tape Reader Needed for Archiving

[BitWiz]

I have just acquired a number of PDP-8 paper tapes. My reader/punch is not working at the moment (neither is my PDP-8 but that's another story).

I am looking to beg, borrow or buy a paper tape reader or reader/punch (stand alone or PC04) so that I can archive these tapes as they are getting more and more rare.

I would prefer a serial (RS-232) reader or reader/punch but I could deal with a parallel and create my own parallel to serial converter or get some kind of USB to parallel adapter.

There are several "hand pull" types of readers out there (like the OP-80A) but I am afraid of damaging the very old fanfold paper tape by using my inconsistent hand rather than some kind of motor driven mechanism which is designed for smooth paper tape flow.

Does anyone have any ideas or something they have to sell or donate?

Please contact me by email directly.


Thank you,

Mike Katz
bitwiz@12bitsbe

 

[bzotto]

Not sure what to make of the email domain above, replying here. I have a motorized reader that I picked up and repaired to do a similar archiving project (not DEC stuff). I'm not local to you and can't part with it for the time being but just FYI if you can't find another solution and are willing to entrust the tapes to a roundtrip by mail (and are perhaps not in a terrible hurry), I'd be happy to help out.

 

[1944GPW]

Even if I set the baud rate right down low on my late 70s/early 1980s EECO paper tape reader, it doesn't treat the tape kindly. Instead of pulling the tape slowly it just zaps it through in high-speed bursts of a second or two duration, and pauses while the buffer is sent. The lower the baud the longer the pause. I would not be surprised if this action happens on other tape readers.
If I needed to be super careful with a fragile tape I'd go the hand-pulled route with perhaps a LEGO motor / rubber tires geared down low to very slowly pull it through.

 

[vrs42]

For archiving, you'd ideally want to use a reader with optical sensing rather than sprocket feed. Nice rubber rollers to pull the tape along, and a feedback mechanism to detect that the tape is jammed (not advancing) before the rollers tear it.

My reader is sprocket feed, and nowhere near Mike, but it does have a lovely sensor that detects resistance to the sprocket advancement.

There's not a lot of reason to be concerned about buffering and baud rates, as any laptop should be able to write the data to a disk file long before it is necessary to block input. At least at any speed at which it is remotely safe to move the tape.

Vince

 

[BitWiz]

Thank you all for your advice.

I have purchased a Sanyo Denki sprocket fed reader on ebay for $25. The interface is simple (8 bit parallel, 1 bit for start/stop, 1 bit for forwared/reverse, 1 bit for data strobe (actually 3 of them but I only need 1), 1 bit for error. Maximum tape speed is 270 CPS but can be controlled by strobing the start/stop.

I'm thinking of using a Raspberry Pi Pico with a display to create either a parallel to serial tape controller or a parallel to USB CDC (USB Serial).

The unit has one quirk though, it will continue to send 0xFF's (377's) continuously after the end of the tape. I'm thinking of adding some kind of optical sensor to detect the end of tape.

Many thanks to Chuck Guzis for his help and recommendation.

I'm just hoping for $25 the unit is actually functional. Though thee are more on ebay at different price ranges.

If anyone has a better solution or a working PC04, please let me know.

P.S My email address is bitwiz@12bitsbest.com

 

[Chuck(G)]

You can single-frame that Sanyo Denki, however. It all depends on the width of the enable signal. These things were pretty rugged, so you shouldn't have problems.
Depending on the model, yours may require +12 and +5 or +24 and +5. There's documentation on Bitsavers for at least one model. I programmed my firmware to turn the feed off after about 50 consecutive 0xff frames.

 

[BitWiz]

I think the one i am getting is +24 and +5.

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I think I have some edge connectors that I can make work.

The documentation says that the run signal must go low before the end of the data sync pulse.

For non-continuous operation (run signal always high) all I have to do in software is something like this

Loop
Set run signal high
If data strobe
Set run signal low
Read data
end if
wait delay for speed ( 1 CPS would be 1 second, 10 CPS would be 100mS, full speed, 270 CPS, is 3.7mS)
end loop

 

[Chuck(G)]

You said you were doing this for a PDP-8. Does that mean that only 6 or 7 bits of a frame are used?

 

[BitWiz]

You said you were doing this for a PDP-8. Does that mean that only 6 or 7 bits of a frame are used?

There are four paper tape formats generally used by the PDP-8:

1. Leader/Trailer - Only punched in column 8 (0x80, 2008)
2. RIM Format - No column 8 punch but a column 7 punch every 4th row
3. USASCII Format - Full 8 bit ASCII (some PDP-8 programs only use the lower 6 bits of the ASCII code)
4. Binary Format - No column 8 punch and an occasional punch in column 7 (to indicate address rather than data).

 

[DougIngraham]

You said you were doing this for a PDP-8. Does that mean that only 6 or 7 bits of a frame are used?

By default the 8th bit was set when you typed ASCII on the teletype keyboard. Most programs would accept text either way. There are programs that get confused if you send lower case by accident.

The other paper tape format I thought of is the Help loader format which uses all 8 bits.

The short answer is that all 8 bits are recognized.

 

[BitWiz]

David,

Thank you for clarifying.

I know that other formats do exist on the PDP-8 and that the PDP-8 reads the full 8 bits but I don't recall or ever knew all of the different formats.

 

[1944GPW]

I know that other formats do exist on the PDP-8 and that the PDP-8 reads the full 8 bits but I don't recall or ever knew all of the different formats.

This page has some diagrams https://trmm.net/Papertapes/
He has some really fabulous projects, it's well worth looking around his site, A while ago I sourced the components for his USB to Teletype 15 boost converter interface to use with my backpack teletype.

 

[Roland Huisman]

I wonder how common the PR/S01 reader is... It has a current loop output and it is painfully slow, but it works...

 

[DougM]

I have a home made manual pull reader you're welcome to borrow if your eBay machine doesn't work out.

it's got a nice USB interface

 

[Chuck(G)]

I didn't think that any of the RPi series had 5V tolerant GPIO. I did my interface with the lowliest of the Blue Pills (about a buck on Aliexpress now)--an STM32F103C6 (32KB flash, 10KB sram) driving a USB CDC-ACM interface--the chip also has a UART available if that was my requirement. So basically, my interface cost about a buck. The PSU cost about $14--the connectors were a little challenging to source. By far, I spend more time building the box that getting the rest of it to work.

But hey, whatever floats your boat...just be mindful of the 5V I/O.