[Hallicrafters] Low power output on some bands on HT-32

[Jim Liles]

Good evening Pat,

Do believe we have a fix for your malady.  It wreaks of a common problem dating back 40 years and seemed to molest most radios.  Take a look at ---- 

http://www.k9axn.com/_mgxroot/page_10875.html  

It describes your symptoms and also the fix.  It is written toward the SR-400 and SR-2000 but it is an almost universal problem with vintage radios.  It’s called a Chassis Loop which happens almost anywhere in these radios.  When we restore a radio every ground is tested and every chassis screw is removed dabbed with copper butter and reinserted.  Prevents 90% of the squirrely problems that will plague you later.      

This problem causes the 12BY7A to turn from an amplifier to an oscillator and your tubes will go red because the 12BY7A is oscillating at a frequency close to the tuned circuit that is supposed to control it --- full drive even with the drive set to “0”.  Usually happens while tuning the pre selector.  

Earlier I suggested that only the bias not the plate or screen voltage would cause this malady.  Of the plate, screen, or bias, that is true unless you radically exceed tube limits.  

One other thing to look at if you plan to buy tubes for your transmitter.  The following note is written specifically for the 8122 but toward the end it segues to the 6146, 6KD6, and 6HF5.  It actually speaks to any tube you might use.  They all have the same issues.  Somewhat explains why you can test a tube and have super emissions yet perform poorly in your radio and generally be less stable.

http://www.k9axn.com/_mgxroot/page_10868.html

If you feel that we’re doing a core dump, yep we’re trying to translate hand written notes from 40+ years ago into readable material that anyone can use.  It’s getting difficult to find people who will work on these great place holders of a great era.

Hope you find it interesting.

Kindest regards Jim K9AXN  


 
------Original Message----- 
From: ciferripatrick at yahoo.com [HallicraftersRadios] 
Sent: Monday, March 09, 2015 9:16 PM 
To: HallicraftersRadios at yahoogroups.com 
Subject: [Something New From Your Hallicrafters Reflector] Re: Low power output on some bands on HT-32 

   


Hi Jim,

Thanks very much for the response.  It appears that my fix of inserting a resistor to lower the 6146 screen voltages to near the 205 volts shown in the manual wasn't the way to go after all.  Doing that lowered the output on some bands by 20 watts.  

I'll do as you've suggested to isolate the problem.  First though, I would like to buy a new pair of finals since the ones I have are all very used and have seen a lot of very red plates while trying to fix that original problem.  Could you recommend a supplier I can contact to get some new ones?

Thanks again,
Pat (WA2P)