[Hammarlund] HQ-170 audio

[Les Locklear]

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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