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4-400A pentode as solid state
4-400A pentode as solid state
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Old 4th January 2018, 03:02 AM   #1
Oneminde is offline Oneminde
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Default 4-400A pentode as solid state

Hello. If anyone can solve or point me in the right direction, that would be make my day.

Basically, what the heck does one need to do or look at in order to make a 4-400A equivalent solid state version which mimics this tetrode in terms of electrical in- and output as well as performance. Since I have no idea, I figured why not reach out for help.

Last edited by Oneminde; 4th January 2018 at 07:14 AM.
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Old 4th January 2018, 06:51 AM   #2
6A3sUMMER is offline 6A3sUMMER  United States
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They would make a lot of people's day if they could.
And I believe it is a real Tetrode, not a Pentode.
Anybody?
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Old 4th January 2018, 01:27 PM   #3
Oneminde is offline Oneminde
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You are right, tetrode not pentode.. sorry
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Old 4th January 2018, 01:47 PM   #4
hpeter is offline hpeter  Slovakia
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any fet has much more steepness that this tube , but this can do 100mhz or more and capable of 4kv...
not sure what parameter exactly you want to mimic
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Old 4th January 2018, 02:48 PM   #5
6A3sUMMER is offline 6A3sUMMER  United States
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hpeter asked a good question.
Do you want to use this for Hi Fi or Guitar amplifier service?
Is power the criteria?
Is sound the criteria?
Is it the ability to draw lots of grid current?

The 4-400A is a beautiful tube. When I went to the local 250 Watt low power AM station as a kid, I believe they used a pair of 4-400As for the modulator amp (push pull) and for the RF output amplifier. The plates were all glowing orange.

The control grid can dissipate 10 Watts (lots of current for a control grid), the screen grid can dissipate 35 Watts. Just the filament alone takes 72.5 Watts and glows like an incandescent light bulb. As a modulator, the plates can take up to 400 Watt dissipation, and as the AM modulated RF class C amplifier 270W plate dissipation.

I once built a stereo single ended amplifier using 4-65 tetrode tubes. All of these direct heated tubes of this family (4-xx, 4-xxx) use thoriated tungsten filaments, and light up very well. I did not have enough voltage and current in the tube to make the plates glow orange-red. The next tube I considered using was a 4-125, but I never tried one; it just takes too much effort for my cup of tea.
The other tube in this series is the 4-250.

Last edited by 6A3sUMMER; 4th January 2018 at 02:51 PM.
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Old 4th January 2018, 02:49 PM   #6
ErikdeBest is offline ErikdeBest  Switzerland
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4-400A pentode as solid state
also curious

Accomplishing 400W dissipation in such a small package will be difficult...
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Old 4th January 2018, 05:27 PM   #7
Oneminde is offline Oneminde
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Quote:
Originally Posted by hpeter View Post
any fet has much more steepness that this tube , but this can do 100mhz or more and capable of 4kv...
not sure what parameter exactly you want to mimic
I can do better and show you parts of the circuit.
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File Type: jpg Plasma Circuit.jpg (96.0 KB, 135 views)
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Old 4th January 2018, 05:30 PM   #8
Oneminde is offline Oneminde
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Quote:
Originally Posted by 6A3sUMMER View Post
hpeter asked a good question.
Do you want to use this for Hi Fi or Guitar amplifier service?
Is power the criteria?
Is sound the criteria?
Is it the ability to draw lots of grid current?

The 4-400A is a beautiful tube. When I went to the local 250 Watt low power AM station as a kid, I believe they used a pair of 4-400As for the modulator amp (push pull) and for the RF output amplifier. The plates were all glowing orange.

The control grid can dissipate 10 Watts (lots of current for a control grid), the screen grid can dissipate 35 Watts. Just the filament alone takes 72.5 Watts and glows like an incandescent light bulb. As a modulator, the plates can take up to 400 Watt dissipation, and as the AM modulated RF class C amplifier 270W plate dissipation.

I once built a stereo single ended amplifier using 4-65 tetrode tubes. All of these direct heated tubes of this family (4-xx, 4-xxx) use thoriated tungsten filaments, and light up very well. I did not have enough voltage and current in the tube to make the plates glow orange-red. The next tube I considered using was a 4-125, but I never tried one; it just takes too much effort for my cup of tea.
The other tube in this series is the 4-250.
See attached circuit. Its a HF high power (RF output amplifier) and it will be used to oscillate at several MHz which is supplied by a carrier signal in the audio spectrum.
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Old 4th January 2018, 06:06 PM   #9
6A3sUMMER is offline 6A3sUMMER  United States
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It looks like a light show that follows the music (entertainment purposes?).
Or it is for some kind of scientific experiment.

In either case it is an AM transmitter, and one that has many watts of radiated power.
The laws of transmitted electric fields are controlled by the country where the transmitter is located.
It would have trouble with meeting EMI regulations if it is to be a commercial product.
There are different regulations for intentional than for non-intentional electromagnetic radiation.

In a properly screened room it may have to meet other regulations, including safety.

The way to build such a device with solid state parts (probably in parallel) is to use more current at less voltage, and then use a voltage step up transformation. Either a resonant pi network,
or an RF autotransformer. This will require a complete re-design of the circuit.
You are right, a search will not find an equivalent part. Even if there were such a solid state device, it would probably be hard to purchase in limited quantity, and would cost much more than the 4-400 that it replaces.

Last edited by 6A3sUMMER; 4th January 2018 at 06:10 PM.
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Old 4th January 2018, 06:40 PM   #10
Matt BH is offline Matt BH  United Kingdom
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Plasma tweeter?
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