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Re: [Amps] SB-220 Output Network

To: Richard Solomon <>,
Subject: Re: [Amps] SB-220 Output Network
From: Mark Bitterlich <>
Date: Thu, 12 Aug 2021 18:29:18 -0400
List-post: <>
Of course the Henry was a Pi-L tank, but the tune cap was a split stator 29-145 
pf cap at 4500 vdc. 
-------- Original message --------From: Richard Solomon <> 
Date: 8/12/21  6:21 PM  (GMT-05:00) To:  Cc: Amps group <> 
Subject: Re: [Amps] SB-220 Output Network With the increase in Plate Voltage 
you will need a bigger (spacing) TuneCap also.73, Dick, W1KSZOn Thu, Aug 12, 
2021, 3:15 PM Mark Bitterlich <>wrote:> 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 
 mailing listAmps@contesting.comhttp://>> 
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