TU58 / DECtape II: Capstan goo

Jay Jaeger cube1 at charter.net
Tue Dec 7 21:48:42 CST 2021

On 12/7/2021 4:38 PM, Jan-Benedict Glaw via cctalk wrote:
> Hi!
> Some time ago, I got my hands on a DECtape II, though no tapes.
> That'll change after a long time and in a few days, even multiple
> tapes will come in.
>    With that drive, I started some first tests. It's PSU seems to be
> all fine, providing stable 5 and 12 V.
>    It's board's wire wrapping is in factory settings, so baud rate etc.
> is all known.
>    However, when I checked the two drives capstans, they're old. One
> has a crack, and as things go, they feel partially either hard or
> gooey. Are there recommendations to exchange these for new ones? I
> also noticed that one of the two motors rotates quite freely
> (both unconnected from the board, so I'm sure they're not magnetically
> braked) while the other ... can be turned without any unreasonable
> torque, but it won't continue to spin at all.

I made some up using some two layer rubber hose from Home Depot, 
sanded/ground down to the proper diameter.

>    Also, when the tapes arrive, are there recommendations in case their
> drive belts are gone?
>    And a final question: There are three firmware versions archived for
> the TU58 control board. It's a known version:
> jbglaw at charon:~/customers/Glaw/VAX/DECtape II$ md5sum *.bin | sort
> 0e5f30a960e72c9d64174a4da8f48f50  23-294E2-00.bin
> 5e059396f779aef9cd80bc75a36c90b2  23-089E2-00.bin
> 5e059396f779aef9cd80bc75a36c90b2  jbglaw-DECtapeII-ROM.bin
> a407fbb5aaa4823a92dd2bc374d1d3ae  23-389E2-00.bin

Interesting.  I have no idea which ones I have.  Maybe earlier versions 
came out for the PDP-11 before the VAXen?

> I guess I got the oldest version? Were there board changes, or could I
> put in a compatible 2Kx8 ROM with any of these versions?  I guess any
> firmware will probably work "good enough", but if I'd avoid known
> problems (are the differences known?), I'd rather avoid them.
>    But after all, I'm quite happy that all the bits'n'pieces will come
> together in a few days.  Yay!
> MfG, JBG

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