[Amps] Henry 2k-4 HV inductor

David Harmon k6xyz at sbcglobal.net
Tue Dec 12 16:13:48 EST 2017

Henry amp iron was notorious for being failure prone in that era....I
know....I lost the choke in my 3K-A after just over 2 years....out of
A guy at the Henry factory told me their iron was mfgd in a guy's garage in
West LA and was not the best at the time.
I bought the Dahl choke when those guys were still in business....1980.
I don't remember the inductance but I still have the amp and it has been
fault free since then...I bought it NIB from Henry and picked it up at their
factory in 78'.
These days....I would get your original re-wound to the same spec by
Does great work.


David Harmon
Sperry, OK

-----Original Message-----
From: Amps [mailto:amps-bounces at contesting.com] On Behalf Of Elliott L
Sent: Tuesday, December 12, 2017 2:52 PM
To: amps at contesting.com
Subject: [Amps] Henry 2k-4 HV inductor

Hi All,

I recently purchased a Henry 2k-4 with a high-voltage fault. The fault has
been traced to the inductor, L201, which is located directly after the
bridge rectifier.

The value, according to the schematic (I have the same PDF that most of you
have, with K9ARZ's stamp on the cover) is 8 Henry, 700mA.

Peter Dahl lists a 2k-4 choke "exact replacement" part for this amplifier,
but the value is 10 Henry. I called up the company and they verified that
the manufacturing directions do indeed specify a 10 Henry choke, and also,
that their copy of the 2k-4 schematic shows the value should be 8 Henry.

So my questions is two-fold.

1. How critical is the value of this inductor to begin with? Is there some
intentional resonance with the parallel capacitor? Wouldn't the RF be fairly
snubbed out already from C49, C48, and L11? My intuition says that the value
is not super critical, and that 10 Henry is probably better than 8, all
things considered. Looking at the wiring at this DC stage, it doesn't look
like a high-tollarance tuned circuit.

2. The original part inside the amplifier has this writing on it: "14405
FERRODYNE 13821" Does anyone have a reference for what the intended value
actually is? Other Henry amplifiers in this line (2k-x, 2k-classic, etc)
have 8 Henry, so I am inclined to believe that 8 Henry is correct, but a
reference back to the original part would be pretty good evidence.

And more ancillary question, the original is rated for 700 mA. Would that
likely be intermittent or continuous?

Thanks very much (and great mailing list!),

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