[Hammarlund] HQ-150 Problem

[Bill Stewart]

Interim Report:
Tnx Tom (N0JMY) & Rodger (WQ9E) for your input. Both of you are thinking along the same lines. I made some quick tube changes this morning (6C4, 5U4G & OC3), but the problem still exists (Rodger, it does use a 6C4). I noticed that the VR tube only shows glow when first turned on and then fades out...no glow noted afterwards or when I am adjusting the sens. pot. The rcvr works fine except for the quirk. At the moment I have a RME-69 on the bench...as soon as its finished (or it finishes me), I'll take a closer look at the HQ-150. I like to try the simple things first (ie, chg tubes). Thanks for the input and I'll pass along any thing I find.

Rodger, you are right about the HQ-150 being a bit unique. I also don't recall any other Hammarlunds with xtal filter and Q-mult. I really like those features and love it for cw. I have 7 HQs and the 150 is becoming my favorite. 

Tnx again guys for the help.

73, Bill K4JYS

----- Original Message -----
From: "Rodger Singley" <rbsingl at ilstu.edu>
To: "Bill Stewart" <cwopr at embarqmail.com>, "hammarlund" <hammarlund at mailman.qth.net>
Sent: Monday, March 22, 2010 8:19:35 PM GMT -05:00 US/Canada Eastern
Subject: RE: [Hammarlund] HQ-150 Problem

Bill,

When you change the cathode bias of those tubes you are slightly affecting the current draw.  The voltage regulator in the receiver should keep the voltage stable on the regulated oscillator circuits but if the rectifier is growing weak or if the VR tube is on the way out then regulation will be lost.

Does the HQ-150 also use a 6C4 for the HFO?  I have the slightly later HQ-160 which does use that tube as do the HQ-170/180 line.   The 6C4 in these receivers is well known for causing issues like this so it could very well be the problem.

I would start by making sure that the VR tube is "firing" and that it stays ionized as you change the RF gain control; it is normal for it to grow dimmer or brighter as the current load changes.  If it is lit I would first substitute a new 6C4 if you have one.  If that doesn't work then try a different VR tube as they do lose their ability to properly regulate as they age.  If the VR tube isn't firing then a weak rectifier is probably the fault.

I have most of the Hammarlund receivers but not an HQ-150 which seems like a rather unique receiver with both a crystal filter and a Q multiplier; I believe it may be the only receiver with that combination built-in.

73, Rodger WQ9E 


-----Original Message-----
From: hammarlund-bounces at mailman.qth.net on behalf of Bill Stewart
Sent: Mon 3/22/2010 5:17 PM
To: hammarlund
Subject: [Hammarlund] HQ-150 Problem
 

My HQ-150 has been working just fine until recently.  Now, on any cw/ssb sig (weak or strong), everything is fine until I adjust the sensitivity control upward into the 8-10 region. In that area, the cw tone freq. changes (probably around a kc) and wobbles a bit (I can use the sens. pot as a fine tuning control). I only get the freq change when I rotate the sensitivity pot into that area. Below that point, I can change the sens. pot with no problem. If I need to, I can adjust the BS and get the freq back to my desired listening tone and it will stay there...until I adj. the sens. pot again. A week or so before this happened there was some freq. jumping going on. I don't think the freq of the rcvr is changing, just something to do with the bfo tone freq. I see the wiper of the sens. pot (R39) feeds the cathodes of the 6BA6s (V2, V4). I changed the 6BA6s but ND. When I get a clear spot on the bench, I'll do some voltage checks around the 6BA6s. 

In the mean time, I'm just trying to get an idea before I lug the thing into the house. Has anybody run into this problem or got an idea about a fix. 

Thanks, Bill K4JYS   
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