[AMRadio] Heath Apache symptoms

James M. Walker chejmw at buffalo.edu
Wed Jan 7 21:25:02 EST 2009

If I might make a suggestion,
Check the ground lugs around the clamp tube and vicinity.
Make sure they are tight, and also check for any signs of

"Three working Apaches and counting."

----- Original Message ----- 
From: "Mike Sawyer" <w3slk at verizon.net>
To: <k5pgw at yahoo.com>; "Discussion of AM Radio in the Amateur Service" 
<amradio at mailman.qth.net>
Sent: Wednesday, January 07, 2009 9:08 PM
Subject: Re: [AMRadio] Heath Apache symptoms

> Hmmm, as an Apache man my self, 9 chances out of 10 I would say check out 
> in
> and around that clamp tube. It almost sounds directly related to heat, (Ip
> goes up the longer the radio is keyed). Might be some bad R's. When you 
> find
> it, post your findings here since I for one would be very interested.
> Mod-U-Lator,
> Mike(y)
> ----- Original Message ----- 
> From: "John King" <k5pgw at yahoo.com>
> To: <amradio at mailman.qth.net>
> Sent: Wednesday, January 07, 2009 7:03 AM
> Subject: [AMRadio] Heath Apache symptoms
> Hello, fellow AM folks! I would like to hear from those intimately 
> familiar
> with the Heath Apache.
> I think my Apache needs some TLC. It is working and gets good reports on
> strength and audio, however:
> I note that when keyed up, after loading and dipping the finals, that the
> plate current starts out lower than the tune up and then starts creeping 
> up.
> My experience over 50 years as a Ham has convinced me that creeping plate
> current is usually a sign of screens in the final tubes going bad. In fact 
> I
> once had a Hallicrafters HT 32B that had creeping plate current when the
> 6146 tube screens began  going bad. In fact, if I didn't increase the bias
> on the tubes, they would eventually "run away" and self destruct. The 
> finals
> in my Apache do not "run away" they just go from lower current at tune up
> and rise to slightly more current than at tune up.
> I think that my grid drive is also marginal because it takes all the
> available grid drive to set it at the rated and desired level of drive. 
> The
> drive control must be at extreme maximum, fully clockwise. This could be
> related to "creeping plate current". What do you think?
> In addition, I note some downward movement of the plate current of the 
> final
> amplifier upon modulation. Lack of grid drive may cause this problem if I
> remember correctly. In addition, I seem to feel that over coupling of the
> output of the final tank circuit might also contribute to the downward
> modulation? I recently replaced the 6AQ5 clamper tube but did not readjust
> the circuit after replacement.
> I would like some input from you who have the knowledge and experience to
> discuss these symptoms. I want to have this discussion before I start 
> trying
> to wrestle this Green Monster out of its' cabinet. I am not as strong as I
> was when I became a Novice over 50 years ago. Before you laugh, let me say
> that if you are LUCKY, maybe you will live to get WEAK!! Hi!! HI!! You may
> address this issue off the reflector if you prefer. I don't want to bore 
> the
> other members with a topic that may not be of interest to them. After all,
> the majority of hams feel that AM is a relic of the past. I enjoy AM, SSB
> and CW. Thanks in advance and 73, John, K5PGW
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