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Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.
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I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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Hi Billy, I'm not an amplifier guru. I've studied & repaired a few. There's a notion in the RF amplifier camp that says "if your amplifier needs more than one tube, you need a different design." I agree with that line of thinking.? If you're going to make the leap from triode to tetrode at the 400 watt /tube?dissipation?level, consider the 4CX400 or Russian GS-36b. They can be had for ~$100 each. Look into the mods online for the AM-6154 / AM-6155 FAA amplifiers as a starting point.
Thanks,
Robin Midgett K4IDC
On Fri, Dec 27, 2024 at 8:03?PM Billy Pickering via <pickeringw= [email protected]> wrote: Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.
?
I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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I would get the 3CX800 checked out and if good go with that. Socket is the same, filament voltage would need changed and maybe the bias. That should be it. Look at all the Alpha amps that have been changed from 400 to the 800 tubes. Must be a good reason.
Hi Billy, I'm not an amplifier guru. I've studied & repaired a few. There's a notion in the RF amplifier camp that says "if your amplifier needs more than one tube, you need a different design." I agree with that line of thinking.? If you're going to make the leap from triode to tetrode at the 400 watt /tube?dissipation?level, consider the 4CX400 or Russian GS-36b. They can be had for ~$100 each. Look into the mods online for the AM-6154 / AM-6155 FAA amplifiers as a starting point.
Thanks,
Robin Midgett K4IDC
On Fri, Dec 27, 2024 at 8:03?PM Billy Pickering via <pickeringw= [email protected]> wrote: Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.
?
I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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I cut my teeth bringing an old Johnson Thunderbolt back from the grave.
(2) 4-400A tetrodes in parallel....learned a lot.
Key to that whole applicaiton is the neutralization....and the fact
if the gains of the tubes are so far off theres not really a perfect way to neutralize,
merely adjust the cap for "best effect" so there is no self osc, and max power out.
I believe ALL the RF transmitting tubes on the market are now made in Chyna,
and they always mass produce with sub-par materials from a "copied" sample
to cut their expenses as much as possible.
They seem to be also renumbering some tubes as "High performance",
merely giving the same tube a different part number with higher price
meanwhile theres no history of that part number tube or a datasheet.
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
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----- Original Message ----- From: "Robin Midgett via groups.io" <RobinK4IDC@...> To: < [email protected]> Sent: Saturday, December 28, 2024 10:21 AM Subject: Re: [ham-amplifiers] Amp modification Hi Billy, I'm not an amplifier guru. I've studied & repaired a few. There's a notion in the RF amplifier camp that says "if your amplifier needs more than one tube, you need a different design." I agree with that line of thinking. If you're going to make the leap from triode to tetrode at the 400 watt /tube dissipation level, consider the 4CX400 or Russian GS-36b. They can be had for ~$100 each. Look into the mods online for the AM-6154 / AM-6155 FAA amplifiers as a starting point. Thanks, Robin Midgett K4IDC On Fri, Dec 27, 2024 at 8:03?PM Billy Pickering via groups.io <pickeringw= [email protected]> wrote: Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have
any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into
modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have
screen power for these tubes, and was wondering if anyone was currently
making the GM3SEK tetrode control boards. I guess we could come up with
something from scratch, but those boards are really nice.
I guess if it really come down to it, we could modify to run the single
3CX800A7 we have, but not sure if the tube is any good as it was pulled
from a commercial unit.
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Main reason for looking into the 4CX250 is I have a ton of them, like 10-12 of them, sockets and chimneys as well.
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My father-in-law who is also my elmer built an amp around the RF deck of a KWS-1 that had been destroyed in shipping which is why we have so many of those tubes. The Henry has the power supply in it and everything else, just not the tubes.
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Sell your 4CX250's and purchase the 3CX400's ?
Main reason for looking into the 4CX250 is I have a ton of them, like 10-12 of them, sockets and chimneys as well.
?
My father-in-law who is also my elmer built an amp around the RF deck of a KWS-1 that had been destroyed in shipping which is why we have so many of those tubes. The Henry has the power supply in it and everything else, just not the tubes.
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Can't beat the simplicity of a triode amplifier.
Sell your 4CX250's and purchase the 3CX400's ?
Main reason for looking into the 4CX250 is I have a ton of them, like 10-12 of them, sockets and chimneys as well.
?
My father-in-law who is also my elmer built an amp around the RF deck of a KWS-1 that had been destroyed in shipping which is why we have so many of those tubes. The Henry has the power supply in it and everything else, just not the tubes.
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The tetrode boards aren’t particularly complicated if you only implement the screen current trip. On my tetrode amplifier, I eliminated the control grid current trip and ALC circuitry. Their primary purpose is providing regulated screen voltage with most of the larger components placed off the boards. The schematic diagrams are still available on G3SEK’s website so spinning up an equivalent set of PCBs — perhaps just one PCB is all that’s needed — should not be difficult.
Mike WB2FKO
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On Dec 27, 2024, at 9:03?PM, Billy Pickering via groups.io <pickeringw@...> wrote:
? Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.
?
I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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I have ran into a couple of those online. Wanted to put one in my Thunderbolt,
as it uses the gas filled tubes to regulate the screen, but I was gonna try a string of Zeners
soldered into an old tube socket as an experiment.
Then I learned if you over drive the input of the amp with too much RF,
you will get screen current and the result is IMD splatter.
The new fancy amps seem to be able to detect this, and they disable the tube
somehow - probably by putting the tube into cutoff via the control grid I guess.
--
Steve Hearns [ KA2PTE ]
Technotronic Dimensions, VT [USA]
WWW.TECHNOTRONIC-DIMENSIONS.COM
E-Mail: Steve@...
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----- Original Message ----- From: "Mike WB2FKO" <mph@...> To: < [email protected]> Sent: Friday, December 27, 2024 10:19 PM Subject: Re: [ham-amplifiers] Amp modification The tetrode boards aren?�?t particularly complicated if you only implement the screen current trip. On my tetrode amplifier, I eliminated the control grid current trip and ALC circuitry. Their primary purpose is providing regulated screen voltage with most of the larger components placed off the boards. The schematic diagrams are still available on G3SEK?�?s website so spinning up an equivalent set of PCBs ?�” perhaps just one PCB is all that?�?s needed ?�” should not be difficult. Mike WB2FKO On Dec 27, 2024, at 9:03?�?PM, Billy Pickering via groups.io <pickeringw@...> wrote: ??? Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice. I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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Hi,? Would anyone have the G3SEK schematic and PCB drawings for download?
The link seems to be broken for me:
Cheers, Mike Peace VK6ADA
The tetrode boards aren’t particularly complicated if you only implement the screen current trip. On my tetrode amplifier, I eliminated the control grid current trip and ALC circuitry. Their primary purpose is providing regulated screen voltage with most of the larger components placed off the boards. The schematic diagrams are still available on G3SEK’s website so spinning up an equivalent set of PCBs — perhaps just one PCB is all that’s needed — should not be difficult.
Mike WB2FKO On Dec 27, 2024, at 9:03?PM, Billy Pickering via <pickeringw=[email protected]> wrote:
? Well, I was lucky enough to pick up a Henry Tempo 2006 that did not have any tubes. Yes, 3CX400A7 tubes are expensive so we were looking into modifying it to run 2 or 3 4CX250B tubes instead. I know we need to have screen power for these tubes, and was wondering if anyone was currently making the GM3SEK tetrode control boards. I guess we could come up with something from scratch, but those boards are really nice.
?
I guess if it really come down to it, we could modify to run the single 3CX800A7 we have, but not sure if the tube is any good as it was pulled from a commercial unit.
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http://www.ifwtech.co.uk/g3sek/
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Well, I picked up the amp and it looks pretty much complete minus the tubes and vacuum variable which I have already found one.?
I was looking at some of the Russian tubes and found that they have a 3CX300A1 with the same pin configuration that I can get for around 80 plus shipping. Just need to look at the specs closer and run the numbers.
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An 'A1' triode is a Low Mu Tube and will NOT work as an amplifier at Radio Frequencies. Like Medium Mu Triodes, designation ending in A3 and A5 also will not work in RF Amplifier service They are used as oscillators. Power Grid Triodes used for Amplifiers have designations ending in A7.
BTW Russian 3CX300A1 make very nice audio Amplifiers tubes for High End Stereo Systems.
On Thu, Jan 2, 2025, 5:53?PM Billy Pickering via <pickeringw= [email protected]> wrote: Well, I picked up the amp and it looks pretty much complete minus the tubes and vacuum variable which I have already found one.?
I was looking at some of the Russian tubes and found that they have a 3CX300A1 with the same pin configuration that I can get for around 80 plus shipping. Just need to look at the specs closer and run the numbers.
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Low mu triodes are useless for GG.? ?Reason is...... they require a stupid high amount of bias V? to obtain normal idle current.? ?You can see that effect asap, by looking at the constant current chart.?
And with obscene amounts of bias used........ you then require? sky high? amounts of drive power..... to overcome the sky high bias V? used.? ?The total gain of the tube is reduced to minuscule.
On a side note, bigger metal Eimac triodes like the H3 versions ( socketless,? and instead used a big grid flange and a pair of cathode lugs)? can be sent to Econco...... where they can replace the low mu grid with a high mu grid.?
Ok, then you have the ultimate, high Mu triode...sans the megabuck socket.?
Econco was recently bought out.? Dunno if the new owners still offer the? conversion service.?
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Robin Midgett
Technotronic Dimensions
Mike Peace