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 <nss@mwt.net> Date: 8/12/21 1:42
PM (GMT-05:00) To: Nidhog <robrk@nidhog.net> Cc: Amps group
<amps@contesting.com> 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.>
http://www.ifwtech.co.uk/g3sek/ <http://www.ifwtech.co.uk/g3sek/>>>> Sent from
my iPad>>> On Aug 12, 2021, at 12:57, Joe <nss@mwt.net> 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>>>>
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