Mellotronists

In a message dated 20/05/2007 19:11:42 GMT Standard Time,  caddyfam@... 
writes:

On your  headblock are 35 tape 
heads.  That is there are 35 coils able to  store energy. Assuming 
you are demagging headblock removed from machine, a  good practice, 
the coils can pick up a residual static charge.  Think  of them if 
you will as capacitors.  So before you plug heads into  preamp, they 
need to be drained.  This is what the resistor does, but  you can do 
the same thing by shorting out the lead at headblock and the  head 
receptacle on preamp with same results.


Dear All,
 
The thing that screws up head blocks is DC voltages as this can partially  
magnetise the heads, turning them into 35 tape erasors!
 
DC can be applied in several ways. The most common are testing the  
continuity with a meter and the residual charge that builds up on a preamp when  the 
headblock is disconnected. For that reason a head block should never be  
disconnected or reconnected while the machine is powered up.
 
The other way to magnetise the heads is to switch off the demagnetiser  while 
it is still in range...
 
When reconnecting the headblock short the input of the preamp (the edge  of  
plug can be used) and then plug the headblock in without delay.
 
Regards,
Norm