Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: 4X150 compared to 4CX250?  (Read 24335 times)
G0KSC
Member

Posts: 8




Ignore
« on: December 09, 2007, 11:14:08 AM »

Hi, I do not have a lot of knowledge aout valves amps but have just bought a well made amplifier for 6M using 2x 4x150s I understand that 4CX250's are a direct replacement, is this true? also, is there much in the way of a power gain in doing a change? Currently the amp gives a little over 600 watts out.

Thans in advance!

JJ G0KSC
Logged
K0BG
Member

Posts: 9832


WWW

Ignore
« Reply #1 on: December 09, 2007, 12:00:30 PM »

4x150s are glass enveloped, the CXs are ceramic. They will indeed plug into the same socket, but that's about the end of the similarities. If you have an RSGB or ARRL Handbook, you can look up the differences.

At 600 watts out of a pair, undoubtedly the amp is class C, and unsuitable for SSB.

Alan, KØBG
www.k0bg.com
Logged

G0KSC
Member

Posts: 8




Ignore
« Reply #2 on: December 09, 2007, 12:31:56 PM »

Thanks for the reply. I had read somewhere that they coudl be swapped with minimum adjustment...
Logged
N3JBH
Member

Posts: 2358




Ignore
« Reply #3 on: December 09, 2007, 03:10:38 PM »

Alan i would be happy to argue that comment with you. they should indeed be inter changable. it would  be like folks adding 572-B tubes in  a 30L-1 amp.

Look up the 2 tubes he suggested and see for your self please. there is know reason why he could not do it. ok sure it may tune  differantly as far as settings but not by a whole lot. here is links to the sheet's to help too see if i am wrong. Jeff

http://datasheets.electron-tube.net/sheets/088/4/4X150A.pdf


http://datasheets.electron-tube.net/sheets/049/7/7203.pdf
Logged
WB2WIK
Member

Posts: 20537




Ignore
« Reply #4 on: December 09, 2007, 05:03:51 PM »

Very interchangeable.  Heater current, interelectrode capacitances and pretty much everything else are the same.  

However, there's a difference between the 4X150 (very old tube!) and the 7034/4X150A.  The 7034/4X150A is rated 2000V Ep, just like a 7203/4CX250B is.  The very old, original 4X150 was a lower voltage tube, only rated about 1200V or so.  I rarely see these in use any more, since they haven't been made in probably 40 years -- or longer.

The primary difference between the 4X150A and the 4CX250B, other than the glass vs. ceramic envelope, is the 4CX250B has a more efficient anode cooler which has a lower Rthj-a, making it easier to cool; as such, the 4CX250B is rated 250W anode dissipation, while the 4X150A was rated only 150W anode dissipation.  But the "guts" of the two tubes are very similar.

I've used them interchangeably in VHF-UHF amps for 40 years now, and even a pair of 4X150As will easily produce 600W output on VHF.  A pair of 4CX250Bs will produce 1kW PEP on VHF, on 144 and 222 MHz, and just a bit less on 432 MHz, in Class AB1 (almost no grid current), with 2kV Ep and 350V Eg2, and do so within their ratings.

My 144 MHz homebrew PP 4CX250B amp will run 1kW PEP output with 6W drive.  It's the circuit from the early sixties ARRL Handbook, "A Plumber's Delight Kilowatt Amplifier for Two Meters."

WB2WIK/6

Logged
G0KSC
Member

Posts: 8




Ignore
« Reply #5 on: December 09, 2007, 11:56:18 PM »

N3JBH, WB2WIK/6,

Thank guys for very constructive comments, I have not received the amp yet but will have a look atthe diagram and power supply voltagesto acertain what is what here and perhaps remove the tubes and take a look to seeif they are 4X150A's.

I am not familiar with a lot of the 'short codes' (eg2 etc)but can fill in the gaps. This one is for 6 meters. However, is there a good on-line resource for home brew amp building?
Thanks again,

JJ
Logged
WA9SVD
Member

Posts: 2201




Ignore
« Reply #6 on: December 13, 2007, 08:28:13 PM »

The 4CX250 series are rated for 2000 Volts @ 250 mA power input, (500 Watts) EACH, so with 1000 Watts DC power input to two tubes, it's hardly unreasonable to expect 600 Watts PEP output in Class AB2.  (Class C would probably yield 700-750 Watts)
    60% efficiency is hardly an unreasonable value for a linear amp with the 4CX250 series of tubes.
Logged
G0KSC
Member

Posts: 8




Ignore
« Reply #7 on: December 13, 2007, 11:34:55 PM »

And in Push Pull??
Logged
WB2WIK
Member

Posts: 20537




Ignore
« Reply #8 on: December 14, 2007, 08:02:48 AM »

Push pull output is the same; in my experience, with enough air you can easily run a 4CX250B at 300mA Ip, and frankly my own power supplies provide 2200Vdc key-down (full load), so I can run one tube at 660Wdc input power.  At 60% efficiency (AB2), that's 396W output, and anode dissipation of 264W, just a slight bit (5%)over the actual tube dissipation rating.

I've run PP VHF amps like this for 30 years and generally they still have the original tubes in them!

Due to the low duty cycle nature of SSB, I have routinely run a pair of 4CX250Bs at 1kW PEP output (AB2) power and see no ill effects; however I haven't specifically measured IMD products, which may be higher than I'd like.

WB2WIK/6
Logged
WA9SVD
Member

Posts: 2201




Ignore
« Reply #9 on: December 16, 2007, 01:36:55 PM »

As Steve said, there should be no difference in output power for parallel, or push-pull arrangements with the same power input for the same number of tubes; as long as  the output circuitry does not introduce significant loss, which can occur in either parallel or push-pull arrangements.  So (staying within the manufacturer's ratings) if each tube can take 1000 Watts DC input, you can expect 300 watts (+/-) for each tube, with 60% efficiency, whether the tubes are connected in parallel or push-pull.  Claims to the contrary, are pretty much "snake oil."  (Of course, inefficient, high loss output circuitry CAN be designed for both parallel and push-pull configurations.)  Push-pull designs CAN be more desirable at higher frequencies, since parallel configurations can lead to (additive) input and output capacitances that are almost impossible to accomodate.
Logged
WA9SVD
Member

Posts: 2201




Ignore
« Reply #10 on: December 17, 2007, 06:38:38 AM »

OOPS!  In the above, make that 500 Watts DC inoput PER TUBE, not 1000 Watts.  1000 Watts input would be for TWO tubes, (although some people push the tubes a bit past that value.)
    600 Watts output for two tubes, whether in parallel or push-pull, is not an unreasonable value for linear operation.
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!