DECTape head problem

[Michael Thompson]

>
> From: Gary Oliver <go at aerodesic.com>
> Subject: DECTape head problem
>
> In debugging my DECtape interface lashup, I found that one of my head
> has two open windings.? Specifically, one channel has an open 'ground'
> with the other two lines apparently the full winding of the channel.?
> The second channel failing has no continuity between any of the three
> lines.? I have tested the other head and it has all the requisite
> continuity so I'm hoping I can at least get a single spindle running.
>
> Has any ever attempted repair of one of these?
>
> -Gary
>

At the Rhode Island Computer Museum we found several DECtape heads on TU55
and TU56 drives with open connections. A volunteer got one head X-Rayed so
we could see the solder joints between the tiny wires for the head coils,
and the larger twinax wires that go to the relay board. We couldn't see any
damage to the wires or solder joints.

We tried heating the potting material to soften it, and digging it out to
get to the solder joints. While digging at the potting material you can't
see the tiny wires, so they will likely get damaged.

We considered using a solvent to remove the potting material, but thought
that it would eat the enamel off the head coil wires and damage them beyond
repair.

So far we haven't found a way to repair the heads.

Michael Thompson