[Hallicrafters] Replacement for a PL-172 in HT-33A?

[Roger (K8RI)]

Carl wrote:
> That is correct and was used in the HT-33B and is interchangable with the 
> glass version.
>
> TMC was a big user of the 8295A.
>
> The biggest problem with swaps is finding a socket and reworking the sheet 
> metal. The Eimac 5CX1500A and B is readily available. Another problem is the 
> cooling, the amp has barely adequate cooling for the original tube and the 
> back pressure is more for any swap.
>
> This is the reason that those amps can be had for $200-250 on a regular 
> basis.
>   
The reason many are low priced is the scarcity of finding a good 
PL-172.  Many of the ones available died a slow death still in an 
unopened box as it slowly went gassy.  Had they plugged them in and 
warmed them up every few months they'd probably still be good. That 
hasn't been a problem with the 8295A, or at least not as much so.  With 
a good working 172, the the 33 A & B models are worth more. With a good 
working 8295A they are worth a lot more.  I never had a problem cooling 
either the stock PL-172 or an 8295A when run within ratings. Users keep 
forgetting this amps was designed for no more than 1 KW DC input and of 
course you tune it like a Tetrode. 

73

Roger (K8RI)
> Carl
> KM1H
>
>
>
> ----- Original Message ----- 
> From: "David C. Hallam" <dhallam at rapidsys.com>
> To: "jack m" <oldvette at hotmail.com>
> Cc: <hallicrafters at mailman.qth.net>
> Sent: Wednesday, February 03, 2010 5:57 AM
> Subject: Re: [Hallicrafters] Replacement for a PL-172 in HT-33A?
>
>
>   
>> There is a metal/ceramic replacement for the PL-172.  I think the number
>> is 8295A.  Later on today when I can get to my Eimac information I will
>> verify the number.
>>
>> David
>> KW4DH
>>
>> jack m wrote:
>>     
>>> Hi - I'm new to this list.
>>>
>>>
>>>
>>> I am tired of looking for a tube for my HT-33A.  Has anyone ever rewired 
>>> their unit, or modified it using a different tube?
>>>
>>>
>>>
>>> Nice as mine is physically, I would like to use it with my 32A/101A and 
>>> I've given up on finding a tube for the prices people expect for a 
>>> probable bad one.  I'm afraid of taking a chance on an Ebay tube.
>>>
>>>
>>>
>>> I though I'd check to see if someone else has gone before me.  I'd sure 
>>> like to hear some details!
>>>
>>>
>>>
>>> Thanks - Jack
>>>
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>>
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