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4CX250K - RF Cafe Forums

Because of the high maintenance needed to monitor and filter spammers from the RF Cafe Forums, I decided that it would be best to just archive the pages to make all the good information posted in the past available for review. It is unfortunate that the scumbags of the world ruin an otherwise useful venue for people wanting to exchanged useful ideas and views. It seems that the more formal social media like Facebook pretty much dominate this kind of venue anymore anyway, so if you would like to post something on RF Cafe's Facebook page, please do.

Below are all of the forum threads, including all the responses to the original posts.

 Post subject: 4CX250K
Posted: Mon Feb 19, 2007 9:47 am 
User avatar

Joined: Fri Feb 17, 2006 12:07 pm
Posts: 343
Location: London UK
Does anyone have a complete datasheet for the coaxial tetrode tube 4CX250K?
Everyman and his dog on the web can sell me any quatity, but no-one gives a datasheet showing which electrode is which.
BTW I have tried the Eimac web site without success, as they just give a photo image and the basic characteristics. I am really looking for the full data, preferably with circuit design graphs.


 Post subject:
Posted: Mon Feb 19, 2007 10:58 am 
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Joined: Tue Dec 26, 2006 5:39 pm
Posts: 58
4cx250 K ? Cannot find that. Here is 4cx250B
The load-line graph is a scan that is not very high quality.

 Post subject:
Posted: Mon Feb 19, 2007 11:10 am 
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Joined: Fri Feb 17, 2006 12:07 pm
Posts: 343
Location: London UK
The 4CX250K is the same as the 250B electrically, but mechanically it is fully coaxial, and so does not use the same B8F/SK610 8pin base. It has annulus rings like the 2C39BA.
However, I cannot find anywhere which rings are the screen grid, which the control grid and which the cathode.
The heater rings are obvious enough -doh.

 Post subject: 4CX250K connections
Posted: Wed Feb 28, 2007 4:00 am 
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Joined: Wed Feb 22, 2006 3:51 pm
Posts: 120

It's simple - you can't cross concentric circles without shorting or breaking them.

So after the heater, going out from the center, you have the cathode, the control grid, the screen grid, and of course the upper enclosure is the plate. They can't come in any other order, because they're rings - cylinders - and the structure of a vacuum tube determines the positioning of the electrodes and their connections.

Good Luck!
Fred AC7--

 Post subject:
Posted: Thu Mar 01, 2007 4:48 pm 
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Joined: Fri Feb 17, 2006 12:07 pm
Posts: 343
Location: London UK
I had not appreciated the internal construction as well as the outside was entirely planar concentric cylinders.
Alimentary, my dear Watnot 8-)

Thanks Fred

 Post subject:
Posted: Wed Sep 12, 2007 7:02 am 
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Joined: Thu Jan 11, 2007 12:59 pm
Posts: 23

I have found a datasheet for the 4CX250K tube, but it's in "paper-format". Are you still interested? I'll can scan it and mail it to you directly.

 Post subject:
Posted: Fri Oct 05, 2007 7:07 am 
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Joined: Fri Feb 17, 2006 12:07 pm
Posts: 343
Location: London UK
Hi Jens
Sorry for late reply. I have been on vacation and away from internet access.
(Difficult to achieve these days.)
I have now found the data sheets thanks. All is clear.

Posted  11/12/2012
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