[Hammarlund] BC-779 Question
Al Parker
anchor at ec.rr.com
Sat Jan 6 16:14:31 EST 2007
Hi Joe,
I think Ed has answered your concerns well, tho' I'm not sure about
the bathtub caps' reliability. The later ones they used in the SP-600's
are often very leaky. I have had mica caps fail, in a BC-779 and other
younger radios, so be wary of them. Check the grid voltages on the AF
tubes, should all be negative, if not that'll point to leaky coupling
caps, causing hot tubes, and audio distortion.
I've just re-read my webpage on the work I did 4+ yrs ago on my
BC-779, I didn't do the bathtubs, but I don't mention whether or not I
tested them. You might want to take a look at that page, I hope it'll be
of some help.
http://www.boatanchors.org/SP200.htm
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>
Cc: <hammarlund at mailman.qth.net>; <milsurplus at mailman.qth.net>
Sent: Saturday, January 06, 2007 10:44 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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