[Hammarlund] HQ 180 repair cont. (more questions)

[JM/CO]

It is important that you obtain the correct manual for your radio. I have
the same one that you do ( serial 1335 and above), so can't comment on your
lack of Z2, other than to say that this is a ceramic module that contains
resistors and capacitors. I have never known one of these to go bad, but
anything is possible. It is used as a coupling / EQ network between the
First audio stave ( V-16 ) and the audio output (V-17). Your radio probably
has this same circuit, but made up of discrete components.
To locate the source of the audio noise, clip lead pin 7,1 of the 6AQ5
(V-17) to ground. If the noise stays, your problem is associated with this
tube. Do not discount the output transformer as the culprit. If the noise
goes away, do the same to V-16. Clip lead pin 1 to ground and see what
happens. If the noise goes away, it's cause lies before this stage. If not,
the problem lies somewhere between V-16 and V-17.
Hope this helps.
Chuck N1LNH
----- Original Message ----- 
From: <Tubsc66@aol.com>
To: <hammarlund@mailman.qth.net>
Sent: Saturday, September 13, 2003 6:54 PM
Subject: [Hammarlund] HQ 180 repair cont. (more questions)


> Hello,
>     First let me start by thanking all of you who've passed along advice
> on my current project, I feel I've made some progress but Im far from
> understanding the persistent problem with my receiver...
>     I've tried to solve the audio problem first, the sizzling noise is
> still there, though I did find a disconnected cap that connected to
> pin 7 of V16 (6AV6), but reattaching it had no affect on the noise...
> The manual refers to a part called Z2 (a "RC printed network"), what
> is this and where is it located? I examine the wiring but I have no
> idea what the manual is refering to. The manual I have says it
> covers serial no.'s above 1335, mine is serial no 680, is it likely
> there were substantial circuit changes along the way that would
> explain this? I have tried a different audiotube to verify its not the
>  source of the noise. In regards to the problems associated with V8
(6BV8),
> the resistance measurments for pins 6 and 3 are way off where
> they should be. Im tempted to simply replace all the ceramic discs
> in this area since I cant isolate which one it is (C39, C42 and C43)...
> Is it likely the 6BV8 is to blame even though it tests "good"?
>     Any and all advice will be welcomed.
>
> 73's
> Chris  KC5IIE
>
>
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