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Re: [Amps] SB-220 Output Network

Subject: Re: [Amps] SB-220 Output Network
From: Richard Solomon <>
Date: Thu, 12 Aug 2021 15:21:15 -0700
List-post: <>
With the increase in Plate Voltage you will need a bigger (spacing) Tune
Cap also.

73, Dick, W1KSZ

On Thu, Aug 12, 2021, 3:15 PM Mark Bitterlich <>

> You might consider looking at the network design values of the Henry 3k
> that used a pair of 3-500's. Both the 3k and 3k-A ran those tubes with
> about the same plate voltage you mention. They could exceed 2K key down
> output with a lot of drive, but were also were probably into distortion.
> It's just a thought, but why reinvent the wheel?
> -------- Original message --------From: Joe <> Date: 8/12/21
> 1:42 PM  (GMT-05:00) To: Nidhog <> Cc: Amps group <
>> Subject: Re: [Amps] SB-220 Output Network
> Thanks,Will check it out.It's all working and has worked perfectly without
> any issues of any kind for over 2 years now. No arc's nothing at all. it is
> just to make it have a well you know the load cap is in a good spot you
> have to run 1400+ watts.And want to finally be able not to have to.Joe
> WB9SBDOn 8/12/2021 12:28 PM, Nidhog wrote:> You are trying to put a 427 in
> a Vega.> Go read a handbook or go here.> I don’t have a Microslop computer
> to do the software.> Mouse down and do his Pi net design.> Bet there’s
> others, on the net.> <
>>>>> Sent from my iPad>>> On Aug 12, 2021,
> at 12:57, Joe <> wrote:>>>> Hopefully some of you here may
> remember my adventures with this SB-220.>>>> I'm the one that ran RTTY at
> full power in a RTTY Contest and >> literally melted down the HV
> transformer.>> And in the process toasted a LOT of other stuff with it.>>>>
> So a complete re-build and change of the HV section was needed.>>>> So
> after looking at what a Pair of 3-500Z's can actually do, I >> decided to
> try to get all I can from them.>> Think like a Big Henry Amp.>>>> I looked
> at the Eimac data sheets. And found a suitable HV transformer.>>>> This amp
> now has 3800 volts at rest on the plates and at full load >> 3600 to 3700
> volts.>>>> Problem is, running this much higher voltage has changed the
> values >> of the output network components needed to be to obtain a match
> now.>>>> It was discovered that on EVERY Band, until the amp is making 1400
> >> watts or MORE the load control wants to be fully meshed, max amount >>
> of "C" available.>>>> Once it gets above 1400 watts, then you can get a
> peak on output >> power when adjusting it.>> But it is still a very small
> less "C" like 5% less than maxed out.>>>> So a simple thought was add more
> "C" so added a nice variable in >> parallel with the load cap.>> This cap
> was about 1/2 the value of the main load cap, so thought >> this should be
> plenty.>>>> I was amazed to see that if it made any change at all, it was
> very >> minimal.>>>> So with discussions with many on this group and
> elsewhere, it was >> decided that because of the higher voltage, this amp
> needs more "L".>>>> That is a major re-do for sure so I set that on the
> side. So >> continued to use the amp at 1400 watts or more.>>>> Thats been
> geez 2 years now? The AMP is still running great! But >> often I did not
> need or want to run 1400+ watts, So I bit the bullet >> and decided to try
> to add the More "L">>>> Now I "CAN" just do a poke and not do anything
> Scientifically.>>>> Like on the 10/15 coil, just move the 10 meter tap 1
> turn longer.>> looking at the 80/40/20, coil, It actually looks like I can
> add in >> the coil form up to 7 or 8 more turns! The grooves in the form
> are there.>>>> Give like 15 meters one more turn,>>>> 20 meters 1 turn>> 40
> 2 turns>> 80 3 turns>>>> And just see what happens?>>>> Or is anyone here
> great with all that math stuff that I probably >> learned when I took my
> extra exam in 1980 or so, but have long forgot >> how to do this kind of
> work to calculate the needed components.>>>> But thinking Ok here is a
> stock SB-220  a pair of 3-500Z's>> Stock voltage is what? 2500 & 3000
> volts>>>> With stock caps and the pair of 3-500Z's How much "L" is needed
> on >> each band.>> I would assume that is how much "L" was designed in the
> Kit.>>>> Now raise the voltage to 3600 to 3800 volts.>>>> Now how much "L"
> is needed with the rest still stock?>> for each band?>>>> and using the
> stock 1.75" coil form, how many turns should be the >> best chance of
> working for each band segment?>>>> Anyone willing to try a gander at
> this?>>>> Joe WB9SBD>>>> _______________________________________________>>
> Amps mailing list>>>>
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