Mellotronists

tmoravan wrote:

> OK - before I replace these worn out tapes, how do I know if I did a
> thorough job demagnetizing the tape heads?  I know there's
> magnetometers (gaussmeters) out there, but in fact, has anyone
> measured the magnetic field strength of a tape head when it's
> magnetized and/or after being demagged?
>
> (Just being paranoid - don't want to wipe the high end out testing my
> work).

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 Greetings Tom and everyone,

Alwayd best to demag the heads and headblock when performing
any service in that area.   I recently cleaned/polished heads on
M400/1428 and replaced a suspect tape head.   (Thanks for your
help, KL !) First order of  business was to demag every head ,
since my hand tools were  suspect .

Not sure what field strength of magged vs. demagged heads might be.
VERY tiny, I'd  guesstimate. Zero Gauss for demagged-heads, obviously.

For general Mellotron svc. easiest way to avoid magging the heads
is to install a 47 K-Ohm resistor across the connector inside the
M400 preamp.  Reason for this is to dissipate the charge of
Capacitor  C2 (20uF@6V) each time headblock is removed and
reconnected. This is an old modification first done by Sound Sales
 then by DK and now the majority  of us who own/service Mellotrons.

Cheers,  Jerry Korb (c/o North Country Restorations)