[Drake] AC Hum in TR-4C speaker

[Garey Barrell]

Hi Tony -

There is additional filtering on the +250 line in the transceiver, a 
four section Twist-Lok at C145.  The AC-4 is ok for the transmitter, but 
needs additional decoupling and filtering for the higher gain receiver 
circuitry.  If you don't have an ESR meter, you can just try bridging 
the sections, I'd start with section "B", which is the 'half-round' 
terminal.

IF you need a replacement, Tom at 'hayseedhamfest.com' has them at a 
reasonable price.

I heard that you met my Daughter and her family over at the 'little' 
airstrip in St Charles, or is it in Campton Hills now?

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>


Tony Sokol wrote:
> Happy New Year!
>
>       Before I spend a bunch of time chasing my tail trying to solve an
> AC hum issue in my newly acquired TR-4C, I thought I would try the
> reflector.  I found a pretty nice AC-4 to go with the TR-4C on Ebay.  I
> also found an AC-3.  I just installed the AC-4R kit in the '4 which is
> really nice!  The problem is that there is a noticeable AC hum in the
> speaker all the time.  I hear it when I key the mic. or turn the RCVR
> gain down.  It's always there and fairly loud.  BOTH supplies exhibit
> the same problem even after installing the new AC-4R upgrade.  Now I am
> thinking maybe a tube with a filament to cathode short.   Anybody run
> into this before?
>
> Thanks and have a great 2011!
>
> 73
> Tony - W9JXN
>
>