Value of 7-track TU10

Doug Ingraham dpi at
Mon Sep 19 13:52:59 CDT 2016

On Mon, Sep 19, 2016 at 10:34 AM, Noel Chiappa <jnc at>

> So what do people think the (monetary) value of a 7-track TU10 master drive
> is? I have no idea what these older vacuum-column drives are worth - don't
> recall ever seeing on for sale. This one is in good condition, and has all
> its
> Flip Chips.  The 7-track is a plus in some ways (rarer), and negative in
> others (can't read old 9-track tapes, which are probably more common than
> 7-track).

Whatever someone is willing to pay.  Peripherals are rarer than CPU's.
People tended to hang on to CPU's but not
so much the Peripherals.  If it is in really good shape with controller for
the machine I have I could imagine paying
as much as $3000 for it.  But I could also imagine someone paying a lot
more than that.  Put it up on EBAY with
an unrealistic reserve and see what it would go for if all you want to know
is what it would sell for.  What controller
do you have for it?

My straight 8 had a homebrew controller and I think it was a Pertec 7 track
which I did not get when I purchased
the system.  The tape drive had real value still and was the only piece the
guy I bought it from wanted for resale.
If I hadn't taken the machine it would have gone for scrap at 14 cents per
pound which is what I paid him for it.

This system was used in the summer months from 1968 through 1973 to do
thunderstorm research and data was
collected on DECtape during the storm and then transfered to 7 track and
shipped off to be processed on the Cray.
I have a couple of hundred DECtapes with weather data on them.  Around 30
meg words of data.  I am assuming that
all three drives were used during a data capture session.  One drive would
be writing, One drive would be waiting to
write.  And the third drive would be rewinding and then unmounted and
changed while the others were actively in service.
The Pertec drive was not a data break device and had to be actively managed
so would not have been able to keep up
with the data stream.

Doug Ingraham
PDP-8 SN 1175

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