[Jukebox-list] Rock-Ola Amp 52280-A (Sound runs wide open)

[John D. Taylor III]

David, Ron, mechanical music of S. F., I want to thank all of you for your
help.  Thank you.  The major clue that get me on track was everyone telling
me that the open volume control would cause the problem.  I rechecked the
potentiometers and all the wiring.  As I was getting ready to check the
capacitors, I noticed that the shielding was not connected anywhere to
potentiometer.  I looked at the schematic again, and according to the
schematic and ground is supplied by the shield for the circuit back through
the plug to the ground war on the chassis.  Although it looked like it had
never been attached, at least nowhere that I can see any evidence of it ever
be an attached, I decided to trust the schematic and wire the circuit
accordingly.  I build a jig so that I could test it before taking it back to
the man that owned it.  Anyway, it worked great on the jig.  I am happy,
he's happy, everybody's happy.  I'm especially grateful to this mailing list
for saving me many many hours of troubleshooting.

The thing that I can't understand is, according to the owner it was working,
and all of a sudden it went wide open and he couldn't turn it down.  I
couldn't understand how it could possibly have worked without that shield
ground being connected somewhere. Originally, there was a bunch of wiring
that was ripped out at the bottom of the jukebox, and I was told that it was
all hooked to the speaker outputs for background sound.  It may have been
some type of remote control that had been removed, but the owner never
mentioned it.  Well, it's history now, and once again, my thanks.

John

  -----Original Message-----
From: jukebox-list-bounces at lists.netlojix.com
[mailto:jukebox-list-bounces at lists.netlojix.com]On Behalf Of John D.
Taylor III
Sent: Monday, October 01, 2007 7:56 PM
To: Jukebox mailing list
Subject: RE: [Jukebox-list] Rock-Ola Amp 52280-A (Sound runs wide open)



Opps, sorry guys, but I'm thinking about one thing and talking about
something else.  The Rockola amp is off of a 478 jukebox.  I am also working
on a Seeburg that is an LS1. No wonder I'm having trouble fixing these
things, I don't know what I'm doing.

John
  -----Original Message-----
From: jukebox-list-bounces at lists.netlojix.com
[mailto:jukebox-list-bounces at lists.netlojix.com]On Behalf Of John D.
Taylor III
Sent: Monday, October 01, 2007 8:22 AM
To: Jukebox mailing list
Subject: [Jukebox-list] Rock-Ola Amp 52280-A (Sound runs wide open)



The sound is running at max volume on both channels on this Rock-Ola Amp
52280-A amplifier. When I first pulled the amplifier out of the jukebox it
had a loud hum.  I changed all the electrolytic caps, including the ones in
the cans.  That cleared up all the buzzing and humming, but it left me with
a loud volume problem.  Later, owner told me that that was his original
problem, it was playing loud and they could not turn it down. This new
information tells me that the problem was not any of the changes that I
made. I haven't done a lot of amplifier work, so, I'm not quite sure where
to start,- with the exception of checking the voltages according to the
schematic.  The volume controls ome out okay.

Anybody have any thoughts on this?  I could use any suggestions.

John

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