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Old 7th June 2004, 09:42 PM   #1
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Default 4E27A monster se amp??

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.
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Old 30th September 2004, 05:15 PM   #2
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Martin,

here's a link (i hope) with a little 4E27 info. we use these tubes at work in a 30 year old RF modulator. if you need the data sheets, let me know.

Johnathan...
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Old 30th September 2004, 10:23 PM   #3
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http://www.mif.pg.gda.pl/homepages/f...49/4/4E27A.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
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Old 6th October 2004, 11:25 AM   #4
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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.
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Old 6th October 2004, 11:56 AM   #5
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Quote:
Originally posted by martinab2
.......3 out of the four didn't survive the journey......
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Old 16th October 2006, 12:09 AM   #6
6146 is offline 6146  Norway
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Default 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
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Old 17th October 2006, 11:34 AM   #7
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Default Re: 4E27A triode data

Hi Alex,

Quote:
Originally posted by 6146
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.
Yeah, sure! Thank you for sharing

Tom
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Old 17th October 2006, 08:33 PM   #8
rdf is offline rdf  Canada
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Wow!
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Old 18th October 2006, 12:51 AM   #9
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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
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Old 18th October 2006, 01:24 AM   #10
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Hey $216 is a bargain, thats like what... 1/4 of a 300B?
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