Strange magtape anecdote

nico de jong nico at
Tue Oct 27 00:50:12 CDT 2020

Hi all,

Back in the early 70's I was an operator on an IBM 360/40 with 4 
tapedrives. Nobody could understand that sometimes a tape transfer would 
stop saying "end of tape", mainly around 3 PM, when not called for. It 
was mainly one specific drive, but its two neighbours, one on each side, 
could also behave like this. Tape drive specialists visitied us, 
scratched their heads, and went off again. When the blinds were rolled 
down, the error disappeared. The reason for the strange behaviour was 
that the sun could shine into the machine room when it was in a specific 
position, so it could send some light into the drive, where the tape 
then reflected the light into the sensor, making it believe that it had 
met the end-of-tape marker.

/Nico OZ 1 BMC

On 2020-10-26 17:01, Al Kossow via cctalk wrote:
> "George Dragner always wore a belt with a metal dragon buckle.  He was 
> a colorful character known for pissing off management.  His most 
> famous act was tossing a chair through the window at a customer site. 
> The customer refused to believe that the lack of humidity in the room 
> was screwing up his magnetic tape media.  As the tape heads depend on 
> the moisture from the air to prevent the magnetic oxide from being 
> torn off the media from the friction during a rewind. George broke the 
> window to prove his point.  He was right ! "
> There is a minimum RH specified for tape, but "tape heads depend on 
> the moisture from the air"  ??

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