[Amps] SB-220 Output Network

[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 <nss at mwt.net> Date: 8/12/21  1:42 PM  (GMT-05:00) To: Nidhog <robrk at nidhog.net> Cc: Amps group <amps at 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 at 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>>>> _______________________________________________>> Amps mailing list>> Amps at contesting.com>> http://lists.contesting.com/mailman/listinfo/amps_______________________________________________Amps mailing listAmps at contesting.comhttp://lists.contesting.com/mailman/listinfo/amps