[Amps] 432 Cavity Amps; Thomson TH 331

[Patrick Barthelow]

Friends,

After being offered for free, a Working Pull complete Tetrode cavity TV amplifier on 470mhz,  (Sans power supplies which would have to be built)  and with possible plans to make a moonbounce Amp, I checked on Pricing/Availability of spares, specifically the Thomson  TH 331 power tube.  The Amp is capable of operation far above the legal limit; ~ 7.5KW, so I wanted to know if it is easy to run at a  reduced  1500 watts out.   

Then I would be more comfortable with a Spare Tube around, and checked a vendor to find that the   Large  Thomson TH 331 is no longer made, and the vendor could find no equivelant tube, that was still made.  A surprise to me also was the last price list with the tube, in 2006 showed a price of $8700 list, ea.  Ouch.

My question is,  It it possible to find a similar power tube to  with matching Critical Anode, and other  dimensions that will swap into the matching cavity system, and make cavity tuning changes to accommodate different tube RF circuit  requirements?   Or... maybe impossible with new replacement tube.  Perhaps a lot of TH 331s are out there used?    

If this is not practical to use/modify for Amateur radio Moonbounce use, it is likely to be donated to a Large Dish installation for their use.   I am guessing interplanetary radar use.  Is 7.5 KW output at 432, useful in, say Moon Radar mapping studies? 

Here are photos of the tube, and Cavity cabinet: 
https://skydrive.live.com/?cid=2eb5c45df634a712#cid=2EB5C45DF634A712&id=2EB5C45DF634A712%21783 


73,    Best Regards,       AA6EG,  Pat Barthelow