Hey Bernie-
The headblock must remain electrically isolated from the chassis to avoid this.
Last time this happened to me I had a missing headblock roller (previous owner's fault, which I fixed). Therefore, the headblock was rubbing the chassis, which changed the hum when different tracks were selected. A bad cable can also cause this problem, but it is usually screechy(not good for tapes). Check the w-clips that hold down the headblock, their centering washers may be off-set or worn through, and may be causing the short. You may have to remove the headblock to fix this one.
The track selector mechanism can also cause this short. However, if this is the machine that Jerry Korb refurbished, he probably already fixed this.
Hope this helps, best of luck. More sugar!
-Bruce Daily
From: john barrick <barrickjohn262@gmail.com>
To: newmellotrongroup@yahoogroups.com
Sent: Friday, February 24, 2012 1:55 PM
Subject: Re: [newmellotrongroup] Grounding Issue?
Try putting it in the C position and then wiggle the cable a bit while playing a note. That may reproduce it.
On Fri, Feb 24, 2012 at 2:53 PM, john barrick
<barrickjohn262@gmail.com> wrote:
Maybe the cable going from the head block to the preamp? On Fri, Feb 24, 2012 at 2:45 PM, tron400
<tron400@yahoo.com> wrote:
#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
-
john barrick
∗Leo got it right the first time∗
∗then he added a second pickup and got it righter∗