OT Troubleshooting: Old computers with modern parts

Tom Jennings tomj at wps.com
Fri Mar 11 12:48:45 CST 2005

On Thu, 10 Mar 2005, Loboyko Steve wrote:

> Actually, it's possible to build a reader fairly
> easily. [...]


> The real problem in a paper tape "ecosystem" is in the
> punches, "handling equipment" and the tape itself; I
> got lucky and got a lot of Mylar cheap some time ago,
> as well as some real DEC fanfold and reel tape. Mylar
> tape is now fabulously expensive at retail.

I concur with all you wrote. There are a lot of 1970's era tape
reader mechanisms around, and they're really easy to interface to.
I made one from a Plessey read head (they're common) and a PIC,
basically it steps until it sees the sprocket hole, then outputs
the byte. (Sprocket hole is smaller, therefore you get good

Punches are indeed the harder part. I've got a DSI in decent
shape, nice serial interface for general use, but punch mechanisms
are harder to find, esp. ones easily interfaced. THere seems to be
10 times the number of readers as punches (makes perfect sense in
context of what paper tape was must used fo rin the computer

> Paper tape is a PITA and fun at the same time. I like
> to point out to friends that the data on the
> metallized Mylar tape will be readable (even
> visually!) and usable long, long after their hard
> disks are very deep down in landfills!

Yup! Even the non-oiled paper will last 500 years if it's kept
dry. It indeed suffers in the data-density department but it's fun
to work with on a non-production basis!

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