c29 balance knob question and humm from ear phones

[william13]

I would like to post two separate issues.

ISSUE 1:

When I turn my balance control clockwise from the 12 noon position to the 4pm position ie to the right, my left speakers volume reduces as expected.

When I turn my balance control counterclockwise from the 12 noon position to 8am position my right speakers volume does "not" reduces its volume.

It this a pot issue:

From the manual it reads

"BALANCE and
LOUDness
The BALANCE and
LOUDness controls are
concentric. The BALANCE
control (large
outer knob) adjusts for
equal volume of either
the left or right channels.
The volume of the channels can be varied
relative to each.
left . . . turning the control to the left accents the
left channel by reducing the right channel output.
right . . . turning the control to the right accents
the right channel by reducing the left channel out"

ISSUE TWO:

There is a hum with both earphone jacks: Music can be heard. There is no hum when speakers are used. Is this a grounding issue?

Thank you

Bill

 

[jlovda]

It has been my very limited experience with shipping Mcintosh units that when front panel glass is broken around a knob, the unit was subjected an impulse type shock against the front side that momentarily pushed a knob against the glass. It tends to rebound back out and you scratch you head looking at the 1/8" clearance. This happened to me with an MR77 I bought off ebay from a dealer in Seattle using UPS. (I got my money back). If that is what happened, I would not be surprised if the shaft for that control damaged an internal wiper(s). Sort of like hitting the end of the shaft with a hammer like a nail head. My guess. Someone may have a better idea. There are four pots (2x balance & 2x loudness) with a concentric shaft so it would be a lot of work but you might need to remove it and measure the four sections.

I wish you luck. A unit with visible damage can sometimes have hidden damage.

 

[william13]

found a picture of the balance control

Here is what the part looks like. Lots of room for damage