[Hammarlund] HQ-170 audio

Thu Feb 24 20:28:09 EST 2011

Why not start by pulling the tube that precedes the volume control?

Bob Macklin
K5MYJ
Seattle, Wa.
"Real Radios Glow In The Dark"
----- Original Message ----- 
From: "RAY FRIESS" <rayfrijr at msn.com>
To: <leslocklear at cableone.net>; <1oldlens1 at ix.netcom.com>; 
<hammarlund at mailman.qth.net>
Sent: Sunday, February 20, 2011 5:22 PM
Subject: Re: [Hammarlund] HQ-170 audio

>
> Les ..   The 170A uses an OA2 voltage regulator.
>
> One reason I thought the audio or driver is that even with the volume 
> control all the way down, I can still hear the static crashes, just not as 
> loud.
> It would seem to me that if the noise was generated prior to the audio 
> section, with the volume control down, it would go away entirely.
> The fact that it remains with the volume all the way down, would seem to 
> indicate that it is being generated either in the audio driver, or the 
> audio output
> because it is still audible.  With the volume control down there should 
> either be nothing driving the audio output tube, or if it were in the 
> driver tube the
> noise being generated in the driver was being supplied to the audio output 
> tube.
>
> I must admit that I have never seen a voltage regulator tube cause static 
> crashes, so I find that interesting Les.
>
> In my experience, I have found tubes exhibiting microphonic noise 
> response.  Usually a tube presents that problem due to the elements 
> wiggling or aging
> and becoming susceptible to vibrations such as occur with the tapping of a 
> front panel, chassis or cabinet.  The vibrations are transmitted into the 
> tube,
> causing the microphonic sounding noise, which sounds different from the 
> "static crashing" type of noise one hears from a bad tube.
>
> I have used the "tube tapping test" over the years too.  I havent tried it 
> yet because I will have to pull the receiver out of its position on the 
> operating bench.
>
> My thoughts on making the inquiry about anyone having spare ones to part 
> with was to get ready in case it comes down to that being the cause.
>
> Ray
>
>
>
> From: leslocklear at cableone.net
> To: 1oldlens1 at ix.netcom.com; rayfrijr at msn.com; hammarlund at mailman.qth.net
> Subject: Re: [Hammarlund] HQ-170 audio
> Date: Sun, 20 Feb 2011 18:40:14 -0600
>
>
>
>
>
> I have seen voltage regulator tubes make static crashing noises on several 
> different receivers, including a R-390A and SP-600. I don't have a book 
> handy, does the 170A use an OA2 like the 180A? Swap regulator tubes just 
> to eliminate that as a source. Or, tap on the tube with a wooden lead 
> pencil eraser.
>
> Les Locklear
> Gulfport, Ms.
> DX'ing Since '57
>
>
>
>
>
>
>
>
>
> ----- Original Message ----- 
> From: Richard Knoppow
> To: RAY FRIESS ; hammarlund at mailman.qth.net
> Sent: Sunday, February 20, 2011 6:30 PM
> Subject: Re: [Hammarlund] HQ-170 audio
>
>
> ----- Original Message ----- 
> From: "RAY FRIESS" <rayfrijr at msn.com>
> To: <1oldlens1 at ix.netcom.com>; <hammarlund at mailman.qth.net>;
> <boatanchors at puck.nether.net>
> Sent: Sunday, February 20, 2011 3:35 PM
> Subject: RE: [Hammarlund] HQ-170 audio
>
>
>
> The microphonics are still present even with the volume
> control all the way down.
> The noise (static like crashes) decrease with the volume
> control all the way, down but are still present, just barely
> though.
> By microphonics, I mean that when I tap the cabinet or front
> panel, you can hear the coming through the audio section.
> Before the noise started in the audio section, it was not
> present.
>
> I have had the receiver gone completely through by an expert
> in Hammarlund receivers.  When he sent it back after going
> through it,
> he said it was as close to factor specs as he had ever been
> able to get a receiver of its age to.
>
> Ray
>
>     There may be two different problems. If the "static"
> goes away with the volume control down its generated ahead
> of the audio stage. You may be able to isolate it by pulling
> tubes to see what makes the noise go away.
>     The microphonics may be from a bad tube but I again
> suggest tapping and poking at things to see if you can
> isolate it. Without another tube to substitute its difficult
> to isolate it to the tube but even if another tube works
> better it may be that the socket or tube pins are oxidized
> which can also cause a similar microphonic problem. Cleaning
> the pins with a toothbrush or even a Brillo pad and cleaning
> the tube socket with some Deoxit and then working the tube
> in it may help.
>     Don't count on your "expert", there may still be
> problems.
>     Neither of the audio tubes is rare or expensive and a
> web search should find some at reasonable prices.
>     Unfortunately, few tube testers have any means for
> testing for microphonics. I will say that its normal for
> tubes to have just a little but not what you describe.
>
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
>
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