[Boatanchors] Interminable Hum!

Rinkie Pollack rinkies at att.net
Fri May 31 11:27:10 EDT 2013

I have an R55A which has had the same  problem.  If I remember, it was a bad ground somewhere.  That's what I'd check first.  Don't just tighten the screws; remove and clean under them
Ron K2RP

--- On Fri, 5/31/13, Wilson <infomet at embarqmail.com> wrote:

From: Wilson <infomet at embarqmail.com>
Subject: Re: [Boatanchors] Interminable Hum!
To: AWFremmer at aol.com, boatanchors at puck.nether.net
Date: Friday, May 31, 2013, 8:00 AM

Tack a cap across the filter sections, especially the last one.
Independent of volume suggests it's on the power to the output amp.


-----Original Message----- From: AWFremmer at aol.com
Sent: Friday, May 31, 2013 10:53 AM
To: boatanchors at puck.nether.net
Subject: [Boatanchors] Interminable Hum!

Fellow Collectors/Restorers,

Decided to swallow my pride and come to the experts for  help.  I have an
Allied Knight
R-55A with a hum problem that I've been unable to  resolve.  I think I've
isolated the source to the preamp  tube, 6AW8.  Swapping the preamp tube with
the amp tube does not help.  When touching the shield of the tube, before
it gets too hot to hold, I can  diminish the hum but not eliminate it.The can
electrolytic runs cool to the  touch even with the radio on for hours.  I
don't own a capacitor checker  but the usual ohmmeter test on all four
sections results in the expected  downward defection and slow upward return to a
high value of resistance.   The hum is independent of the volume control
setting and the receiver plays  strongly enough that the hum is simply an
annoyance but one which I can't  stand.  All screws have been snugged up.

A search of the Internet came up with the following web site,
(http://www.ohio.edu/people/postr/bapix/r55a.htm) .   Rich, KB8TAD appears to have had the same problem but his solution,
running a  ground wire from the preamp socket to another point on the
chassis did not  help.

I also own the R-55 which does not exhibit this  problem.

Suggestions?  And many thanks in advance for any  help.

73, Alan - KB2HEI
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