[Hammarlund] HQ129X Distortion

[jeremy-ca]

The answer is very simple. Since the 129X has three IF stages instead of two 
as in most radios they used a lower gain tube. The 6SK7 simply overwhelms 
the detector and the as designed AVC circuit.

Having owned a few 129X's on and off over the past 50+ years Ive never had a 
problem obtaining NOS mil surplus 6SS7's.

Carl
KM1H

----- Original Message ----- 
From: "Larry Asp" <larry.asp at sympatico.ca>
To: <hammarlund at mailman.qth.net>
Sent: Friday, April 04, 2008 5:59 PM
Subject: [Hammarlund] HQ129X Distortion


The subject of audio distortion  with the rf gain control turned up full on 
the HQ129X has come up a few times, and the standard advice given has been 
to back off the rf gain control. This problem existed with my set up until 
today, even though I have gone through it and replaced all the paper caps 
etc. What often happens with the HQ129 is their owners replace the  4 6SS7 
tubes in it with one or more 6SK7s. The 6SK7 does work in the set and gives 
it a bit more gain (some say), but its not an exact substitute. Such was the 
case with mine - one of the 6SS7s had been replaced with a 6SK7. I had the 
good fortune of purchasing some NOS 6SS7s recently (JAN type) and replaced 
the 6SK7 and the  old  6SS7s with with them, and - the distortion went 
away - except for the signal from a broadcast station (10KW) located about 
2 - 2 miles from my house (which I can control by backing off the RF gain). 
Hope this helps - worth a try if you can find the tubes.
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