[Amps] Subject: Henry hum on transmitted signal

Tue Sep 5 19:19:08 EDT 2023

I bought a new 3K-A in 77' and picked it up at the factory in West LA....still have it.
The choke went to ground in 80' taking out the overload relay(s).
Fortunately, I was able to get a replacement overload relay direct from Ohmite.
This relay assy was discontinued but I was lucky and the guy at Ohmite swept the floor and assembled a new one for me no charge....still working today.
Some years back some guy in Hawaii was parting out another 3K-A so I got another relay assy from him as another spare.
Peter Dahl was still in business back then so I bought a replacement choke from him and it is still working today....likely forever too.
While I was at it....I got rid of the antenna changeover relay with the dime sized contacts and went to see the nice folks at RF Parts and picked up vacuum relays and Agastadt timer.
The amp still has the original transformer and every time I use it I hold my breath.....
Some guy at the Henry factory told me that the chokes and transformers were made in a guys garage out in Lakewood I think it was, and were known to be low quality....jeeeze

More recently I got a 3K Classic X MKll with it's own hum problem which is a fairly well known mfg problem with these units.
It was a bit sneaky but fairly easy to fix and it has been working great now for about 10 years.

Dave Harmon
K6XYZ
Sperry, OK.

-----Original Message-----
From: Amps <amps-bounces at contesting.com> On Behalf Of Steven Katz
Sent: Tuesday, September 5, 2023 5:54 PM
To: gudguyham at aol.com; Rob Atkinson <ranchorobbo at gmail.com>; amps at contesting.com
Subject: Re: [Amps] Subject: Henry hum on transmitted signal

Yeah, I wouldn’t do that.   The Henry pedestal amps were well built and built to last, although the HV choke resonating cap is a failure point…usually after 20-30 years, not a year.

I never had any problems with any of them, but never owned one for 30 years.

The 4K Ultra was IMO the best amateur amp ever made by anybody but didn’t cover 160 meters, so that was its primary drawback.   I had one for about ten years, zero problems and it was hard to keep it down to “legal limit.”  😊

From: gudguyham at aol.com <gudguyham at aol.com>
Sent: Tuesday, September 5, 2023 4:53 PM
To: Steven Katz <stevek at jmr.com>; Rob Atkinson <ranchorobbo at gmail.com>; amps at contesting.com
Subject: Re: [Amps] Subject: Henry hum on transmitted signal

Steve, I won’t mention any names, but somebody bought quite a few Henry amps and stripped out the ENTIRE power  supply guts, plate transformer , choke, HV cap, and the tuning caps  even the wire would step start gizmo.  Sold off all that stuff and put in a cap input supply using PD transformer like Ilona the big Ameritrons.

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On Tuesday, September 5, 2023, 5:26 PM, Steven Katz <stevek at jmr.com<mailto:stevek at jmr.com>> wrote:
Lou, I've seen that, too.

I've also seen the resonating cap short out (choke is still fine) and B+ soar to 6kV and they just keep operating.

Something will eventually fail, but those big oil-filled caps can often handle 6kV for quite a while, and so can the tubes in many cases.

-----Original Message-----
From: Amps <amps-bounces at contesting.com<mailto:amps-bounces at contesting.com>> On Behalf Of gudguyham--- via Amps
Sent: Tuesday, September 5, 2023 4:24 PM
To: Rob Atkinson <ranchorobbo at gmail.com<mailto:ranchorobbo at gmail.com>>; amps at contesting.com<mailto:amps at contesting.com>
Subject: Re: [Amps] Subject: Henry hum on transmitted signal

Rob, it seems as though is not “if” but “ when” the choke craps out in those Henry amps.  I’ve seen where many chokes shorted to the core and guys mounted the choke on insulated material instead of getting a new one. Lou

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On Tuesday, September 5, 2023, 7:14 AM, Rob Atkinson <ranchorobbo at gmail.com<mailto:ranchorobbo at gmail.com>> wrote:

I think the resonant choke design is clever by a half.  It's just too finicky and failure prone for my liking.  Also, I've seen a choke Henry used in one of their amps, I forget which one but it was supposedly rated for 700 ma.  I have  a 700 ma filter choke out of a 1 KW broadcast rig intended to run continuously and it's at least twice as big and heavy as the dinky thing Henry used.  I've seen I don't know how many RF power amplifiers designed for volatile loads like SSB and CW and they did fine with nothing but around 40 mfd capacitance for a filter.  I would only use a choke input for power supplies serving transmission modes that put the supply under continuous load, such as AM and RTTY.  I would rebuild that power supply for whatever xmission mode is intended and ditch that resonant choke scheme.

73

Rob
K5UJ
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