Have a few 4E27A transmitter tetrodes in my collection and am trying to figure out whether there is any way of making them play tunes.
Triode mode maybe? max screen voltage is 750 although plate is rated for 4000!! Does anyone know how well these tubes work in triode mode? I only have plate curves as tetrodes. Was considering 700v with 5k transformers.
Plate curves when operated as a tetrode look quite nice for 2000v / 250mA load line. Obviously there would be huge safety issues to consider and I'm not really planning to build this one but... Could it be done? what about output transformer design, rf oscillation etc ?
It would be good to hear from anyone who has tried this sort of tube.
Triode mode maybe? max screen voltage is 750 although plate is rated for 4000!! Does anyone know how well these tubes work in triode mode? I only have plate curves as tetrodes. Was considering 700v with 5k transformers.
Plate curves when operated as a tetrode look quite nice for 2000v / 250mA load line. Obviously there would be huge safety issues to consider and I'm not really planning to build this one but... Could it be done? what about output transformer design, rf oscillation etc ?
It would be good to hear from anyone who has tried this sort of tube.
http://www.mif.pg.gda.pl/homepages/frank/sheets/049/4/4E27A.pdf
Let's see... screen around 4-500V would do it. 1kV 125mA is max., but that's a bit low on current so maybe 800V plate. At 500Vs, you'll want around -45V grid bias, for 150mA Ip. Call saturation 1 or 200V, that's delta 600V, peak about 300mA = delta 150mA, or 4k load resistance. Distortion doesn't look bad, although you'll get the usual odd harmonics... but you need to use NFB anyway. Far end of loadline is around 1300V 20mA, for a full length of delta 1100V 280mA - 38W? Not bad.
Tim
Let's see... screen around 4-500V would do it. 1kV 125mA is max., but that's a bit low on current so maybe 800V plate. At 500Vs, you'll want around -45V grid bias, for 150mA Ip. Call saturation 1 or 200V, that's delta 600V, peak about 300mA = delta 150mA, or 4k load resistance. Distortion doesn't look bad, although you'll get the usual odd harmonics... but you need to use NFB anyway. Far end of loadline is around 1300V 20mA, for a full length of delta 1100V 280mA - 38W? Not bad.
Tim
Thanks for all the information. Unfortunately I was a bit premature in saying that the 4E27s were part of my collection. I had bought them as part of a lot but was waiting on delivery. Sadly 3 out of the four didn't survive the journey damn!
Would still like to try some audio experiments with transmitter tubes though so might be having another look on ebay.
Would still like to try some audio experiments with transmitter tubes though so might be having another look on ebay.
4E27A triode data
Hi, I have measured the triode characteristics for 4E27A. g2 and g3 was tied together and connested to plate with a 100 ohm resistor. Perhaps someone might find the data useful.
Cheers
Alex
Hi, I have measured the triode characteristics for 4E27A. g2 and g3 was tied together and connested to plate with a 100 ohm resistor. Perhaps someone might find the data useful.
Cheers
Alex
Wow indeed. A 5V filament (could work well with AC.) Plate resistance in the 1200 ohm range (could work well with 5k load - a lot of big transmitting tubes won't.)
And Antique Electronic Supply is selling them for only $216 each! 🙁
-- Dave
And Antique Electronic Supply is selling them for only $216 each! 🙁
-- Dave
4e27a
There seems to have been a slight interest in the triode data I uploaded. As I am slightly new to tube amp designing, I was wondering what is the opinion of people here on the forum to the 4E27A (triode coupled) versus the GM70 for constructing a 10-20 W SE amp.
I did not measure the 4E27A with grid more negative than -150 Volt since that was the limit of my power supply.
Cheers
Alex
There seems to have been a slight interest in the triode data I uploaded. As I am slightly new to tube amp designing, I was wondering what is the opinion of people here on the forum to the 4E27A (triode coupled) versus the GM70 for constructing a 10-20 W SE amp.
I did not measure the 4E27A with grid more negative than -150 Volt since that was the limit of my power supply.
Cheers
Alex
I am interested. BTW these are plentiful for 50$ on epay. Its the 4e27 that I am interested in that are more scarce. I would like to understand the differences in op points more. One for 4e27 is 100ma 750 volts 5 k 20 watts the 4e27 is 70pd and the A 125 watts. Which is the better choice? I chose the smaller because of the easier to find output trans but.. The a's are so much cheaper to find on epay. Which is more linear ? the only thing that really matters I guess especially in triode and at a sensible voltage.
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