[Hammarlund] HQ-170 audio

[Richard Knoppow]

----- 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