[Amps] Henry 2k-4 HV inductor

Thu Dec 14 13:46:56 EST 2017

Alright, there were some really interesting comments on this question,
thank you all!

If I were to ditch the HV choke and keep the plate transformer, can I
simply add additional caps in parallel with the existing 20uF cap? Will an
extra 20-40uF do the trick? I see a lot on eBay coming out of Russia.

Also, should I be worried about the increase of inrush on power-on?

I like the idea of ditching the choke, it really does seem unnecessary.

Thanks,

--E
W6EL

On Thu, Dec 14, 2017 at 9:56 AM, Jim Thomson <jim.thom at telus.net> wrote:

> Date: Wed, 13 Dec 2017 21:16:22 -0500
> From: Ron Youvan <ka4inm at gmail.com>
> To: amps <amps at contesting.com>
> Subject: Re: [Amps] Henry 2k-4 HV inductor
>
> <   On 12/13/2017 01:15 PM, Jim Thomson wrote:
>
>   /* snip */
> > ##  Although the  tuned choke concept works, it really is a throwback to
> the
> > 1950s.  IF the choke and parallel resonating cap just happen to resonate
> at 120 hz,
> > the peak V across that parallel tuned choke will skyrocket, and both the
> cap and choke
> > will explode.   Typ the choke is resonated just a bit higher than 120
> hz, like 123 to 124 hz.
> > When u start sucking loads of plate current, the inductance of the choke
> will DECREASE a bit,
> > and the resonance of the choke + resonating cap combo will  INCREASE
> some more, like now
> > up to 124-130 hz.
>   /* snip */
>
>   < I must have been taught all wrong, I was taught the capacitor (to
> <ground) is in series with the series inductor forming a series resonant
> <circuit that conducts the 120 Hz to ground, instead of storing energy
> <like the "brute force" large capacitor. (bank)
> --
>   < Ron  KA4INM -
>
> ##  Nope, the small resonating cap is wired  directly in parallel with the
> choke.  That forms a
> parallel tuned circuit, killing the 120 hz component. Any cap after that,
> that is wired from B+  to
> B- just kills any residual 120 hz components, plus harmonics of 120 hz.
> HV filter caps are not wired
> from B+ to chassis, they are wired directly between the B+ and B-.   Any
> HV meter is also wired
> directly between B+ and  B-.  Old ARRL handbooks will depict HV meters
> wired between  B+  and chassis,
> which is incorrect..and more fubar.
>
> ##  John lyles designed a HV supply for a FM broadcast TX.  For the
> resonating cap, he used the
> .9 uf at 5 kv rated small oil cap  you will typ see in any microwave
> oven.    He used 2 of em in series,
> so  .45 uf at 10 kv.   Both caps sent to the choke maker..who builds the
> resonant choke around the
> .45 uf combo.   On any single phase setup, the component you are trying to
> get rid of is always 2F,
> or in north america, 2 x 60 hz  = 120 hz.    In japan, UK, etc, its  2 x
> 50 hz  = 100 hz.   For 3 phase
> setups, it now becomes 6 F, or  300 hz in the UK and  360 hz  in north
> america.
>
> ##  resonate the choke at 120 hz, and the caps will explode every time, it
> has to resonate just above
> 120 hz.   Ask anybody who has tried it.
>
> ##  the typ NON resonant choke setups back in the day consisted of a pair
> of tube rectifiers, then
> into the swinging choke, then into the fixed choke, followed by a pair of
> paralleled small value oil caps..then the huge bleeder assy.
>
> ##  back in the day, typ HV oil caps were like  2 uf, 4 uf, and  6 uf for
> a big oil cap.   Plate xfmrs back then were high Z types,
> not made for the high peak currents of a high C filter setup.  Typ high Z
> plate xfmrs had a lot of  DC resistance  across the sec windings.
> They also used a CT, since the tube rectifier setup consisted of a FWCT
> config.   The B+ came off of the CT of the fil xfmr.
>
> ##  It isnt 1957 anymore.  Tube rectifiers, high Z, centered tapped plate
> xfmrs, tube fil xfmrs with the HV CT, real small value oil caps,
> fixed chokes, swinging chokes, and resonant chokes have gone the way of
> the do-do bird.   The big hypersil + loads of filter C is the
> ticket. Buddy with the 2 x GS35B on 6m... the B+ only drops 50 vdc under a
> full load of   4.1 kv  and 2A.    Then another 100 vdc drop cuz
> of the 50 ohm glitch assy, which is a necessary evil.
>
> ##  Even the plate xfmr used in my drake amps only has 9-10 ohms across
> its  940 vac sec.
> Its a FWDoubler.  2650 on RX... 2600 on idle, keyed, with no drive, and
> 2520 vdc  with a 800 ma load.
> Its aprx a 850 va CCS xfmr, nothing special.     120 lb pole pigs with a
> 4800 sec typ have a 19 ohm sec.
> My even bigger dahl is just 6 ohms across its  5200 highest tap, and only
>  2.65 ohms across it lowest tap
> at 2300 vac.  My 46 lb dahl is 24 ohms across its  2700 vac highest tap.
>
> ##  I have caseloads of  2100 uf at 450 vdc lytics, and also 2300 uf, and
> also 10,000 uf.   These surplus
> large value lytics are the ticket when used in conjunction with a low Z
> plate xfmr.  HV meter barely flickers on
> ssb.   IMO, henry radio wasted a lot of effort pursuing their FWB +
> resonant  choke   HV supplies.   They ended up
> with heavy console units that typ weighed in at 185 lbs.   The henry 8K
> combo RF deck + pwr supply weigh in at
> 350 lbs, yet the supply is only good for 2 kw CCS rf output.   Heavy yes,
> heavy duty, no.
>
> Jim  VE7RF
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