The Mellotron Group

I'm guessing that when you switch tracks there is something causing the  
head block to ground. Check the retainer springs and make sure that they are  
isolated from the head block channel at the bottom (half-grommet in good 
shape)  and that they do not come in contact with the tape guides. Also check 
that the  head block rollers are properly positioned and in good shape.
 
 
In a message dated 2/24/2012 3:46:02 P.M. Eastern Standard Time,  
tron400@yahoo.com writes:

 
 
 
#500 has had an intermittant hum for a while now. I thought that maybe it  
was related to the volume pedal jack, but I noticed yesterday that the 
volume  of the hum changes when I move the track selector. Track C doesn't seem 
to  have any hum, but Tracks A and B do. Any idea what the cause might  be?

Bernie