Rust on tape heads

From: John Lawson <jpl15_at_panix.com>
Date: Sat Sep 4 13:20:28 2004

On Wed, 1 Sep 2004 pzachary_at_sasquatch.com wrote:

>
> I guess I should have been more specific, and say that 3M company makes a
> line of abrasives that use the scotchbrite technology but are MUCH finer,
> (10000 grit or so I think is the bottom end, I don't use anything finer
> than 1800) and these have supplanted most of the bar substances in the


   Yup - to re-iterate, I have successfully recovered large audio heads
from foriegn-object damage (slipped screwdriver, shipping damage, etc. -
ouch!) by using a strip of cleaned linen to which has been applied a *very
light* paste of mineral oil and jeweller's rouge - or, as mentioned,
some other exceedingly fine grit abrasive powder. This is then 'seesawed'
very gently across the pole faces in the same direction the tape travels

   In cinema audio work, where the heads were typically 30MM tall and have
from one to six poles - the three-track pole faces are 1/4" *each* - after
lapping them, we typically used a short continuous loop of some crap mag
stock, which would run for an hour or two, to 'condition' the head and lap
it in to it's final shape - using the natural abrasiveness of the media
itself to finish the job.

   But none of this is for the faint-of-heart - ya gotta go slow and think
about what is being done, all in terms of a knowledge of the physics and
mechanics of tape-recording head technology. No matter what the signal or
the number of tracks, the mechanical aspects remain the same for all
classes of static-head machines.


   And most certainly you are dead-on about first taking the decision as
what the ultimate end is - is this for a museum? Hobby machine? Critical
application?

  Cheers

John
Received on Sat Sep 04 2004 - 13:20:28 BST