[Hammarlund] BC-779 Question

[Ed Wirtz]

Hi,

I would check the capacitor in question for leakage. That could be the 
reason for the audio distortion. They are known to fail. Also, I don't think 
it is a mica cap. If I remember correctly it is a paper cap but does look 
like a mica in some respects. The large bathtub caps along side are pretty 
fool proof. I believe they are oil filled and don't fail very often in my 
experience. I think 82 pf is close enough to 91 to be Ok.  6K6s are Ok to 
use for the audio amp. The load resistance is a little different but should 
pose no problems.

73 and good luck,

Ed, KØBKA
----- Original Message ----- 
From: "Carole White-Connor" <carolew at bellatlantic.net>
Cc: <hammarlund at mailman.qth.net>; <milsurplus at mailman.qth.net>
Sent: Saturday, January 06, 2007 9:44 AM
Subject: [Hammarlund] BC-779 Question


>
> I'm working on a BC-779B. The radio plays well and has decent sensitivity.
> The audio is not as good as it should be and it's noisier than it should
> be. I sense some distortion and the AVC seems sluggish. (I'm comparing it
> to the civilian SP-210 that I have).  I've already replaced the paper caps
> and about a half-dozen out-of-spec resistors. All voltages are pretty 
> close
> to spec.
>
> I'm looking at C-13, which is a 91 mmf grip-coupling cap. The part list
> specifies that it is a silver mica. It looks like a standard paper cap.
>
> Here are my questions:
>
> 1. Is this type of silver mica of this vintage prone to failure? It looks
> crappy but that may just be the moisture-proofing compound sprayed rather
> liberally on the underside of this set.
>
> 2. The closest replacement I have is 82 mmf. Is that good enough?
>
> 3. Are the .05 mfd bathtub caps along the side of the set prone to 
> failure?
>
> 4. The manual specifies 6F6s for the audio section. The prior owner had
> 6K6s there. Is this good, bad or indifferent?
>
> As always, thanks for your help!
>
>
> Joe Connor
>
>
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