Author Topic: Need help identifying tube  (Read 1257 times)

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Offline profdc9

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Need help identifying tube
« on: August 18, 2022, 07:02:56 pm »
I am trying to identify a tube, in particular, if there is now a source of such a tube from China or Russia as these are likely not made anymore in the USA.

The tube is from a 10 kHz - 250 MHz, 2500 W Amplifier Research Model 2500L MII amplifier. It is one of eighteen tubes in the amplifier finals. The tubes are oil cooled as can be seen by the nipples on the top. The amplifier itself dates from the early 1990s.

The tube is marked

"Amplifier Research"
1003787 - 101C

I have also included the schematic. I was not able to find the item in the BOM corresponding to these tubes however.

Are any similar tubes used in amateur or broadcast amplifiers?


Offline geggi1

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Re: Need help identifying tube
« Reply #1 on: August 18, 2022, 08:32:59 pm »
Have a look at this site.
And this one.
It could be 4cx250 with some kind of liquid cooling device.

Offline Wallace Gasiewicz

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Re: Need help identifying tube
« Reply #2 on: August 21, 2022, 12:35:01 pm »
I agree probably a 250 or even a 350.
Does not look like the "cooler" can be easily removed, for a look at the tube itself

There are several linears that use these tubes but a lot of them have too much amplification to meet the FCC standard for ham amplifiers
I have an old military radio that uses two 250 or 350 tubes in the final (depends on the model)
« Last Edit: August 21, 2022, 12:44:45 pm by Wallace Gasiewicz »

Offline mag_therm

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Re: Need help identifying tube
« Reply #3 on: August 21, 2022, 03:10:12 pm »
Licensed amateurs can build or modify amplifiers "without concern for the certification rules" that manufacturers and dealers have to follow. Such non certified amplifiers can also be resold by dealers but only to licensed amateurs.
Reference: Extra Class License Manual section 3.6 and exam questions E1f03 and E1f12

However operation still has to be within all of the  license class, output power and spurious  emission limits applicable to the band and mode.

Edit Above is for USA, .Other countries may differ.
« Last Edit: August 21, 2022, 03:19:48 pm by mag_therm »

Online T3sl4co1l

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Re: Need help identifying tube
« Reply #4 on: August 22, 2022, 01:44:35 am »

Does seem to be a conduction cooled variant.

Also, holy shit, splitter into matched delay lines into 6x grid lines each, all feeding one common plate line in order?  Amazing; that thing must've been a terrific pain to tune (or design)!

« Last Edit: August 22, 2022, 01:47:42 am by T3sl4co1l »
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Offline CaptDon

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Re: Need help identifying tube
« Reply #5 on: August 22, 2022, 02:30:50 pm »
That 11-pin version came in thermal link conduction cooled versions also. There is a water cooled version of the 4CX250 but the pinout is not the 11-pin version like yours. I think the National NCL-2000 linear amplifier used a pair of the 11-pin air cooled versions. The cost of tube replacement far exceeds the value of the amplifier in today's marketplace and I think you would play hell even finding replacements except through A.R. and they will surely charge 10X their original purchase price from Eimac or Amperex. The A.R. stuff was really untuned broadband and often used in military labs and E.M.I. testing labs where 'Cost was no object'. I was never sure why Eimac changed the basing of the 4CX600 series??? It is physically the same base as the smaller brothers (4X150, 4CX250, 4CX350) but with a different pinout requiring a special socket only available through Eimac. Naturally the Collins military gear used the 4CX600JB tubes with their astronomical price tag!!!! It would have been far cheaper to use 4CX1000 or 4CX1500 variants!!! The first economical water cooled variant across the Eimac line was the 4CW20000.

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Offline coppercone2

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Re: Need help identifying tube
« Reply #6 on: August 23, 2022, 08:38:17 pm »
the air heat exchanger might be able to be modified for oil since the specific heat of oil kinda sucks anyway

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