That answers a lot of questions... I doubt cathode current would ever reach
one amp.
So, essentially adding a DC bucking winding is an academic exercise is and
not needed,
I added the neutralization windings in case they were needed--some earlier
designs did
include neutralization in two tube designs. I may try it just to see bridge
neutralization
produces a null in this amp. The project is a winter pass time and a test
bed to try out
some of my off the wall ideas
The added ferrite bar choke is relatively small and wouldn't work for the
filaments.
Thank you for your time and effort.
On Thu, Jan 4, 2018 at 10:08 AM, <amps-request@contesting.com> wrote:
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> Today's Topics:
>
> 1. Collins 30S-1 Amplifier For Sale (Bob Sullivan)
> 2. Re: Plate Choke Issue (mark bitterlich)
> 3. Toroidal filament choke and DC current (Jim Thomson)
> 4. Plate Choke Issue (Jim Thomson)
> 5. Re: Defining CCS (Bill Turner)
> 6. Re: Toroidal filament choke and DC current (Manfred Mornhinweg)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Wed, 3 Jan 2018 16:12:57 -0500
> From: Bob Sullivan <robert@isquare.com>
> To: "Amps@contesting.com" <amps@contesting.com>
> Subject: [Amps] Collins 30S-1 Amplifier For Sale
> Message-ID: <2CC82404-B435-4B3B-BA0D-6FF7C3D88902@isquare.com>
> Content-Type: text/plain; charset=utf-8
>
> 30S-1 for sale, pickup only in Great Falls, VA.
> See details here (scroll to bottom of page);
> http://www.isquare.com/personal_pages/forsale.htm
>
> Thank you!
>
> 73, Bob
> W?YVA
> http://www.isquare.com/personal_pages/ras-hardware.htm
>
> ------------------------------
>
> Message: 2
> Date: Wed, 03 Jan 2018 17:31:54 -0500
> From: mark bitterlich <markbitterlich@embarqmail.com>
> To: Manfred Mornhinweg <manfred@ludens.cl>, amps@contesting.com
> Subject: Re: [Amps] Plate Choke Issue
> Message-ID: <29.82.30255.CD95D4A5@smtp02.onyx.dfw.sync.lan>
> Content-Type: text/plain; charset=utf-8
>
> I would offer that using an IR temp measurement device (gun), would be
> safer and easier. I've used them for lots of measurements in amps, power on
> in fact. You can stay well away from HV and get accurate measurements. My 2
> cents.
> Wa3jpy
> -------- Original message --------From: Manfred Mornhinweg <
> manfred@ludens.cl> Date: 1/3/18 2:01 PM (GMT-05:00) To:
> amps@contesting.com Subject: Re: [Amps] Plate Choke Issue
> Hi AJ,
>
> > What am I missing?
>
> Let's try.
>
> RF heating?
>
> I just did the maths. With ~30?H and no stray effects you should be
> getting a bit more than 1A of RF current in that choke. The RF
> resistance of the wire at 14MHz is around 4?. So, maybe 6W of heating
> from RF, in addition to some smaller heating from the DC. Not enough to
> blow up a ceramic insulator, I would say. So it's not this.
>
> You said you "looked for any series". I understand you mean that you
> checked for series resonances and didn't find any in the band. But
> that's not the whole story. Did you actually measure the impedance of
> that choke (magnitude and phase) at 14MHz? If not, then try to do so.
>
> I would not be surprised to find such a choke having its main resonance
> far below 14MHz. Which means that at 14MHz it would have a capacitive
> reactance, and possibly a rather low one. In that case the RF current in
> it would be much larger than 1A, and the heating from RF current would
> be correspondingly higher (I?R). That could well make the insulator
> burst from thermal stress.
>
> I assume the ceramic you are using is fine for RF work. If not, it could
> be so lossy that it heats up from the inside. You can detect this by the
> choke measuring a reasonable inductance but a low Q. Or on an impedance
> meter, a reactance in the area of a few kiloohm in series with a
> resistance of more than 10? or so. And when sliding the coil off the
> insulator, the Q gets much better, or the series resistance getting much
> lower. If that's happening, look for a more suitable insulator.
>
> By the way, a longish closewound coil like that one can hardly have a Q
> much higher than 200. Probably less. At 3kV and 1A in it, the reactive
> power in that choke is around 3kW, assuming it's not higher from
> parasitic capacitance. At a Q of 200 that means 15W of RF dissipation,
> and that's pretty much a best-case assumption! If the actual impedance
> is lower due to capacitance, the dissipation will be larger. And if the
> Q is lower than 200, the dissipation will be higher too.
>
> You very likely need a better choke.
>
> Can you measure the choke's temperature after a two minutes transmitting
> or so? Either with a non-contact IR thermometer, or else VERY CAREFULLY
> by quickly shutting down the amp after transmitting, making ABSOLUTELY
> sure all high voltage has been discharged, and then opening the lid and
> touching the choke with your finger. If it smokes and smells like
> barbecue, and you find yourself in dire need of practising your
> vocabulary, you know you have too high loss in that choke. But do this
> finger test ONLY if you have a completely safe discharge system there.
> In the heat of the battle it's just too easy to do something stupid, and
> if you take your time to triple check that the high voltage has drained
> off, the choke will have cooled off too.
>
> The recipe to survival of the choke is very likely a better choke. One
> that has lower RF loss, if possible, and which is large enough to safely
> dissipate that loss. A sharp airflow around the choke would help too.
>
> Manfred
>
> ========================
> Visit my hobby homepage!
> http://ludens.cl
> ========================
>
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> ------------------------------
>
> Message: 3
> Date: Wed, 3 Jan 2018 18:56:14 -0800
> From: "Jim Thomson" <jim.thom@telus.net>
> To: <amps@contesting.com>
> Subject: [Amps] Toroidal filament choke and DC current
> Message-ID: <8F344A0B20374E859E6E51CD7F88A07C@JimPC>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Date: Wed, 3 Jan 2018 14:51:23 -0500
> From: Peter Bertini <radioconnection@gmail.com>
> To: Amps@contesting.com
> Subject: [Amps] Toroidal filament choke and DC current
>
> <I'm building a four tube 813 amplifier and I am planning to use a 240-43
> toroid core for the filament choke.
>
> I've seen some concerns about core saturation due to the DC cathode current
> involved in this application.
>
> I was planning to add a third winding (trifiliar) to allow bringing the
> filament transformer CT back to the top of the windings, thus cancelling
> the DC field. I'd have to add a second ferrite rod choke to fully decouple
> the third winding, but it would be a trivial task.
>
> I was also going use the core to provide a bifiliar winding for
> neutralization, if needed. All windings are 7 turns, which yield about 50
> uH and over 500 ohms Z at 160 meters. Core is wound and ready to go.
>
> Any advice, encouragement, or warnings?
>
> Pete k1zjh
>
> ## A looong time ago I had a hb 4 x 813 GG amp. But it used a .5 inch
> x 7.5 long ferrite rod for the bifilar. Wound with 12 ga magnet wire to
> handle
> the 20 A CCS of fil current. Then a 10 vac at 20A fil xfmr, with CT.
> Zero issues
> with rod saturation with the dc component. Of course there will be zero
> issues with the
> 20A component, since current is always flowing in opposite directions
> due to the bifilar
> design. The magnetic fields cancel.
>
> ## What bands are u using it on ? 50 uh is more than ample even for
> 160m.
> A buddy has a 3x6 metal tube in GG..and 24 uh used for the fil
> choke...zero issues
> on 160m. The 3 Amp dc current component is also a non issue. But in
> this case, 2 x
> identical bifilar rods are used. Any one winding of rod A..is in parallel
> with any one winding
> of rod B.. This is done at the tops and bottoms of each bifilar rod
> assy. 8 gauge magnet
> wire used. Uh does not drop exactly in half either, but a little over
> one half..go figure. Done
> this way, since 8 gauge magnet wire will handle 40A CCS..and 2 of em in
> parallel will handle
> the 80A CCS required by that tube.
>
> ## I use the identical setup on my hb 3CX-3000A7 fil assy, except 10 ga
> magnet wire used.
> 10 gauge will handle 30A CCS, and 2 in parallel will handle 60A. Tube
> fil sucks 50A CCS.
> Plate current is between 1.5 to 2.5 A. I have also seen similar setups
> used on even bigger tubes,
> with 5+ amps of plate current
>
> ## IMO, I cant see even a single 240-43 core saturating from the plate
> current of 4 x 813s, but dont
> quote me on that, as I have no experience using a 240-43 core as a
> bifilar. A buddy used type 43
> torroid cores on his hb 3CX-3000A7 fil setup, using 6 gauge magnet wire.
> Dunno how big in diam the
> core was, or how many used. Dunno if it was used on 160m or not.
>
> ## You could always use 2 x 240-43 cores in a stack, and even less than
> your 7 turns, to get the same uh.
> provided you have the room for the 2 x stacked cores.
>
> Jim VE7RF
>
>
>
> ------------------------------
>
> Message: 4
> Date: Wed, 3 Jan 2018 19:26:52 -0800
> From: "Jim Thomson" <jim.thom@telus.net>
> To: <amps@contesting.com>
> Subject: [Amps] Plate Choke Issue
> Message-ID: <01FC456036B4496080579ED9CBCABB1A@JimPC>
> Content-Type: text/plain; charset="utf-8"
>
> Date: Thu, 4 Jan 2018 07:21:37 +1300
> From: Steve Wright <stevewrightnz@gmail.com>
> To: amps@contesting.com
> Subject: Re: [Amps] Plate Choke Issue
>
>
> On 04/01/18 04:28, AJ wrote:
> > This time I was able to measure where it blew apart, ~20 uh from end to
> > end. I slid the wire off the broken ceramic and slid it onto a new one
> > mounted it in the amp to measure. I am referring to RFC-1
>
> <Well, 20uH in series with the tubes output capacitance is resonant on
> <about 6-8 MHz.? That might be worth exploring..
>
> <S
>
> ## Nope. Tube output capacitance between anode and grounded grid is
> in PARALLEL with the plate choke, NOT in series with it.
>
> ## There is no way in hell a 27 / 31.8 uh choke will have its 1st
> series resonance
> in any HF band. A 50 uh choke, regardless of length to diam ratio,
> will always
> have its 1st series resonance at 35 mhz, well above the 10m band.
>
> ## Henry radio, in its 8 K ultra, using the 3CX-3000A7 tube, used a 2
> piece plate
> choke setup. Large choke was 180 uh, wound with 24 gauge wire. Small
> choke
> was just 20 uh, and wound with 18 gauge wire. Last production units made
> used
> a different 2 choke setup. The original 180 + 20 uh plate choke setup
> was goofy at best.
>
> ## a tube arc on any of the 4 x 3CPX-800?s would not cause the
> destruction of the
> ceramic form he has the smaller choke wound on.
>
> ## His larger choke really requires 2-3 x 4700 pf ceramic bypass caps.
> His smaller choke should have its uh increased to 50 uh. The smaller
> choke
> should ideally use 1-2 x 500 pf doorknob style bypass caps, like a
> HT-50
> or HT-58 series, which are available in 5 kv..and also 7.5 kv.
>
> ## I would like to know what bands each choke is used on, and what type
> of relay he is using to toggle between chokes.
>
> Jim VE7RF
>
>
>
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 4 Jan 2018 07:19:20 +0000
> From: Bill Turner <dezrat@outlook.com>
> To: Amps group <amps@contesting.com>
> Subject: Re: [Amps] Defining CCS
> Message-ID:
> <DM2PR03MB560C74DC20C4ABFC8505001C01F0@DM2PR03MB560.
> namprd03.prod.outlook.com>
>
> Content-Type: text/plain; charset="us-ascii"
>
> ------------ ORIGINAL MESSAGE ------------(may be snipped)
>
> On Sun, 31 Dec 2017 13:40:21 -0600, W7RY wrote:
>
> >
> >Tapped tank circuits are a problem.
>
> REPLY:
>
> The solution is not to tap them. Wind a separate coil for each band
> and orient them 90 degrees to each adjacent coil. Takes up only a
> little more space than a tapped coil and avoids the problem of
> unwanted coupling within the coil.
>
> Join them together on a series of ceramic standoffs and run the joined
> point to the bandswitch. Put the ten meter coil closest to the
> bandswitch of course. Works like a charm.
>
> In my homebrew 8877 amp I used #4 solid copper wire for each coil. Big
> enough to never overheat and rigid enough to be self supporting
> without any kind of braces except for 160 meters. The 160 meter coil
> was so long I did add a third standoff in the center for support.
>
> 73, Bill W6WRT
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 04 Jan 2018 14:49:09 +0000
> From: Manfred Mornhinweg <manfred@ludens.cl>
> To: amps@contesting.com
> Subject: Re: [Amps] Toroidal filament choke and DC current
> Message-ID: <5A4E3EE5.2040501@ludens.cl>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Pete,
>
> > I've seen some concerns about core saturation due to the DC cathode
> current
> > involved in this application.
>
> I just did the maths. Unless I messed up while typing numbers into my
> trusty old Sharp calculator, the choke you describe would run at a flux
> density of 45mT for every ampere of cathode current. This is just a
> first-order calculation, not including nonlinear effects in the ferrite.
>
> Material 43 has a somewhat nasty behaviour with moderate to high DC
> flux, that varies a lot with temperature, so don't try to push it near
> its saturation flux density. But 2A of cathode current would very likely
> be safe with that choke, and I doubt your 813's will pull more than
> that. Probably even 4A would work as long as the core is kept cool, so
> that the more nasty area of that material's behaviour isn't reached.
>
> > I was planning to add a third winding (trifiliar) to allow bringing the
> > filament transformer CT back to the top of the windings, thus cancelling
> > the DC field.
>
> As far as I can see, that would negate the usefulness of that choke!
>
> > I'd have to add a second ferrite rod choke to fully decouple
> > the third winding, but it would be a trivial task.
>
> In that case you could as well wind the whole choke on the rod, and save
> the toroid.
>
> > I was also going use the core to provide a bifiliar winding for
> > neutralization, if needed.
>
> I can't claim being an expert in the field of tubes, but I understand
> that you can use an 813 either in its intended configuration, with
> grounded cathode, grid drive, and high gain, or in grounded-grid
> pseudo-triode configuration, at low gain. If you use grounded cathode,
> you don't need a filament choke, and if you use grounded grid, you
> shouldn't need neutralization. So I don't think you will need that
> additional winding...
>
> Manfred
>
> ========================
> Visit my hobby homepage!
> http://ludens.cl
> ========================
>
>
> ------------------------------
>
> Subject: Digest Footer
>
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> ------------------------------
>
> End of Amps Digest, Vol 181, Issue 8
> ************************************
>
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