HQ-145AX puzzler

[Al Parker]

Hi Wally,
    I haven't looked at the HQ-145 skem, but I agree with your thoughts,
it's probably a bad cap in the AVC ckt, or in the RF or IF coupling caps
between stages.  Micas have been known, by me, to exhibit similar
problems, like intermittent crackling sounds, etc.   A similar problem to
what you found in the audio ckt - could be in that "couplet" in the AVC.
Does the skem show the internals of them?  They're just caps & maybe
resistors as I remember.
    HOpe this is of some help,
73,
Al, W8UT
New Bern, NC
BoatAnchors appreciated here
http://www.thecompendium.net/radio/
http://www.hammarlund.info

----- Original Message -----
From: "Wally Gibbons" <rockwall at SOURCEONEINTERNET.COM>
To: <BOATANCHORS at LISTSERV.TEMPE.GOV>
Sent: Sunday, January 11, 2004 7:04 PM
Subject: HQ-145AX puzzler


> Greetings,
> Just picked one of these up in great condition (and three zenith
> Transoceanics too!) the other day. It needed some minor repairs, the
> little audio coupling circuit between the 12AX7 and 6AQ5 had failed and
> applied positive grid bias to the output tube, frying the cathode
> resistor. Tube still checks ok, amazing!!!
>
> But now, it's problem. It plays fine, then the received level will drop
> (at random, apparently), as will the s-meter reading. If I switch the
> vfo/crystal switch one position off and back to VFO, it comes right
> back. In fact, a good foot rub and then a "spark" of esd which causes a
> pop in the received signal will do the same thing. Any noise burst,
> disconnecting the antenna and reconnecting, will restore the previous
> receive level. I've never had a radio which behaved this way, obvious
> checks (tubes, cleaning the switches, pots) haven't helped. Doesn't
> appear to be a loose connection. Mechanical tapping around doesn't cause
> it to happen, or fix it. Could it be that other printed circuit module
> in the AVC/detector circuits?
>
> Anybody had any experience with this? I've heard stories of intermittent
> mica caps in the bottom of IF transformers and suspect this might be
> that. Any pointers as to where to look?
>
> Thanks.
>
> Wally Gibbons, WB7ASQ
> North Logan, Utah
>
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