Gene Heskett wrote:
On Sunday 10 August 2008, Mogens Kjaer wrote:
Thompson Freeman wrote:
...
As solvents, it is my impression that isopropyl alcohol and ethanol are
very similar. As such, I'm curious if the video engineers have tried
it.
In my spare time (!) I'm involved in a society for restoration
of old, Danish computers.
We have a ½" 9-track tape drive (with SCSI interface, connected to
a Fedora box, bringing it a bit on-topic again).
Some times when reading old magtapes, the heads become very dirty.
Where are the tape being stored? Tape, in higher humidities and temps,
becomes very abrasive, recommended storage is for relative humidity to be
under 25% and temps below 50F. I once was the ACE at a tv station where the
tapes were all stored in between uses in a walkin cooler held at about 45F.
The air conditioner was set for coils at about 34F so they would wring as
much moisture out of the air as possible without freezing up the evaporator
coils. We were getting 5000 hours out of a 1000 hour rated u-matic heads way
back then.
There is a myth that tape suppliers actually have the slightest clue how
there products will behave over time. In the 1980s we stored a room full
of 1" wide Ampex tapes for about 3 years, until we were ready to do some
further analysis of the flight data they contained. The room was run at
the temperature and humidity recommended by Ampex, and the logs showed
this was correctly maintained throughout the 3 years. When we tried
using the tapes, the binding agent for the magnetic material had
degraded and stuck the layers of tape very solidly together. We could
unscrew the side plates of the reels, and cut through the cake of tape
with a hacksaw. The layers were so solidly bonded that the tape remained
a solid lump after this treatment, and could be beaten with a hammer for
a while before starting to break up. If we simply tried unrolling the
tape from a spool, we ended up with a translucent plastic film, and a
lot of flaky brown stuff.
Recommended storage conditions are only quoted to create the illusion
that the tape maker has a clue what they are doing. :-)
Regards,
Steve
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