Mellotronists

kenmerb@... wrote:

>
> Jerry,
>
>     What's the policy / procedure on demagging the heads on a MKII?
> Is it the same as for an M400?  I should know this, but I don't (and
> obviously haven't done it with mine).  KL and I have discussed this in
> the past, but never asked anyone who knew the answer.  Others may find
> this interesting.    Ken M.

_______________________________________________________________

KM and gang,

The headblocks on MK-I and MK-II models are high impedance.
They have approx 10X resistive measurements of the later models.

All solid-state preamps are low-impedance, while true valve preamps
are high impedance. I checked the schematic for PA1 in the MK-I/II's.
There's no cap to worry about  as in the M400's . And the valve itself
is open-circuit until powered-up.

I'll go out on a limb by saying that  Demagging a MK2 headblock
is the same as M400,without the worry of plugging it back in.
Comment is invited,please correct me if in error.

In Frank's Pindertron, the Hi-Z headblocks are mated to balance
transformers,w/o direct connection to the transistor preamp cards.
This config. is also safer than stock-M400 demag. procedure.

Thanks, Gene Stopp, for your input  on magnetic field strength.
I should email a buddy of mine who works at FermiLab in
Aurora,IL on the superconducting-collider. He'd know for-sure !

Cheers, Jerry Korb (looking for the "Z" particle w. Mellotron heads)