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

[Carl]

I wonder how hard it would be to adapt a 4CX1000A/1500B?
Tubes are readily available NOS military surplus and sockets at a resonable 
cost show up at times.
The FU-728F will also work in the 1000A/1500B socket with a simple mod.

The 4CX-1500A is another candidate if the PS area is modified to allow a big 
filament transformer. The 5CX1500A/B and sockets also show up at times.

Ive also heard a few on the air with 8877's.

Carl
KM1H



----- Original Message ----- 
From: <w7apm at mtaonline.net>
To: "jack m" <oldvette at hotmail.com>
Cc: <hallicrafters at mailman.qth.net>
Sent: Saturday, November 05, 2011 7:38 PM
Subject: Re: [Hallicrafters] HT-33A PL-172A Tube substitute modification


> 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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