[Hallicrafters] HT-33A PL-172A Tube substitute modification

[w7apm at mtaonline.net]

Jack,

I suppose you know about the 8295A Eimac? Direct replacement and ceramic instead of glass. I was given a homebrew PL-172 amp at one time from a elmer and got it on the air. (He was scared of it) It worked well and at 2,700 watts out I quit turning up the drive although the amp was willing!
Anyway, I got 4-5 PL-172 tubes with it and only had one fail when I applied the High Voltage. I got impatient and didn't "Getter" it long enough. I still have one of the tubes and thinking maybe some day I will find a use for it. There is an arcticle in the March 1958 QST on homebrewing with the PL-172...

--...  ...--
Marty/KL7AM

--- oldvette at hotmail.com wrote:

From: jack m <oldvette at hotmail.com>
To: <hallicrafters at mailman.qth.net>
Subject: [Hallicrafters] HT-33A PL-172A Tube substitute modification
Date: Sat, 5 Nov 2011 21:56:35 +0000


Hello group,
 
For 5 years, I have patiently searched for a useable PL-172A tube for my HT-33A amp.  3 EBay used PL-172A "wins" have been - well, you guessed right.
 
The PL-172 market is getting worse!  In favor of a winter boat-anchor project this year, I've decided to give up looking.   
 
As much as I would like to keep this near-mint amp original, the desire to actually use it with my HT-32A has won out.  I was discussing this on the air this past week, and the ham on the other end recalled another ham who had converted his HT-33A rig to run one of the ceramic tubes, but he was not a boat anchor afficianado and did not have any details.  He did recall that ham as stating that the socket and chimney/air cooling system, as well as the various voltage supplies, were not all that difficult or complicated to modify and adapt to the HT-33A chassis or design power supplies.
 
Is there anyone out there who knows of this mod, and where could I find the details?  As a "purist", I would prefer to be able to de-modify it in case the PL-172 market improves sometime in the future.
 
Thanks
 
Jack W3RU  		 	   		  
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