[Hammarlund] BC-779 Update Update

[Al Parker]

Hi Joe,
    A shot from the hip -- it sounds like you have no AVC action at all,
it's running wide open no matter what posn the switch is in.  Can you
measure any AVC voltage at any time?  If so, where, and is it getting to
the stages where needed?  Since you say you replaced everything in the AVC
ckt, re-check your work, maybe you got something off/onto where it
should/shouldn't be - happens to everyone sometime.
    The audio gain pot should go to ground at one end and let no audio
thru when it's at minimum.  The sensitivity pot should put -50v on the AVC
line when at minimum, and that should go to the RF/IFstages and cut them
off.
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.boatanchors.org
http://www.hammarlund.info

----- Original Message ----- 
From: "Carole White-Connor" <carolew at bellatlantic.net>
To: <hammarlund at mailman.qth.net>; <milsurplus at mailman.qth.net>
Sent: Sunday, January 07, 2007 8:40 AM
Subject: [Hammarlund] BC-779 Update Update


> Thanks, guys.
>
> Those two 4 ohm resistors go to the filament feeds to the dials lamps
> and the 6N7 tube, probably to equalize current draw. The main problem
> with the power supply, as one of you pointed out, is that the tubes draw
> more than 6A but my power transformer is rated for only 5A. That
> probably explains why the former owner used 6K6s in place of 6F6s (ie,
> less current draw). It looks like I'm either going to have to get a
> better power supply or use a separate filament transfomer.
>
> Now, what about my signal overload issue?
>
> As I was testing voltages, I had the radio in AVC and both sensitivity
> and audio set at zero. Nevertheless, I still got an audible station
> through the speaker. Do you think this points to the sensitivity pot or
> audio pot as the problem? I haven't
> had the front panel off so I haven't tested them yet. Do you think this
> might have something to do with my issues?
>
> I'm running out of ideas. I replaced every cap and every out-of-spec
> resistor in the AVC chain. If I remove the AVC tubes (6H6 and 6SK7), it
> has no effect on performance in AVC mode.
>
> Any ideas?
>
> Joe Connor
>
> _______________________________________________
> List Administrator: Duane Fischer W8DBF
> ** For Assistance: dfischer at usol.com **
> ----
> http://mailman.qth.net/mailman/listinfo/hammarlund
>