[Hallicrafters] Hallicrafters HT-33A

[Carl]

You also didnt check the HV requirements either.

As far as 8122's go, a pair of those would often cost more than a PL-172 
and they would be running about 500V above their max. Even more if the 
rectifiers were changed to SS.

Carl
KM1H


----- Original Message ----- 
From: "Charlie" <pincon at erols.com>
To: <hallicrafters at mailman.qth.net>
Sent: Friday, September 19, 2008 8:03 AM
Subject: Re: [Hallicrafters] Hallicrafters HT-33A


> It would seem to me that a pair of grid driven 8122 tetrodes would be 
> a good choice.  They're still made by Burle (Spelling?) Industries in 
> PA and are currently in use in many medical applications.  It would 
> take a little metal work but they use the same simple socket as the 
> 8874's.  As for chimneys, some red silicon rubber sheet glued in a 
> cylinder works fine. (It was good enough for Alpha)
>
> If you really want to go cheap, how about a couple 4CX-250's ? 
> They're cheap and the sockets readily available surplus.
>
> I haven't checked the filament requirements on any of these which of 
> course is a concern.
>
> 73' Charlie k3ICH
>
>
> ----- Original Message ----- 
> From: "Roger (K8RI)" <hallicraftersgroup at rogerhalstead.com>
> To: "Carl" <km1h at jeremy.mv.com>
> Cc: <hallicrafters at mailman.qth.net>; <gzook at yahoo.com>
> Sent: Friday, September 19, 2008 12:09 AM
> Subject: Re: [Hallicrafters] Hallicrafters HT-33A
>
>
>> Carl wrote:
>>> There are several choices from the USA, China, and Svetlana 
>>> depending on work involved and acceptable expense.
>>>
>>> 4CX1000A, 4CX1500A & B, 4CX1600B, 5CX1500A & B.
>>>
>>> There are also numerous Russian triodes as well as the USA 3CX1000A7 
>>> and the 8877.
>>>
>> If you hunt there are PL-172s and 8295A out there, BUT it may take 
>> some work to find a good one. Most, or many of the PL172s are gassy. 
>> If the guys would stick them in the amps and let them cook every few 
>> months there'd be more good ones.  8295A tubes are the most desirable 
>> and although the PL-172 has a "/8295A" on it a true 8295A is a 
>> ceramic and metal Pentode while the PL172 is glass and metal. The 
>> 8295A is about a 1/2" taller than the PL172 but there's plenty of 
>> room in the HT-33A and B. If you can find either tube guaranteed it's 
>> worth a small fortune and considerably more than the amps sell for 
>> with the 8295As going for about twice the price of a PL172.  Most 
>> pull out 8295As aren't very expensive, nor are the PL172s. The 
>> problem with those 172s is as I stated before, so many of them are 
>> gassy.  I've picked up two HT-33Bs over the years for about $300 to 
>> $350.
>>
>> I don't know of any that are direct "plug-in replacements. The 8877 
>> although rated at 50% more power is considerably smaller than the 
>> PL172/8295A and takes a much better cooling arrangement than what the 
>> HT33 A and B has. That was one of the nice things about the original 
>> tubes. They only needed a fan blowing air up around the tube and 
>> socket.  That fan didn't even have a shroud.
>>
>> I don't know about the other tubes but converting to an 8877 takes 
>> some physical mods with a bit of care to make it look good.  I think 
>> the others are also smaller in diameter.
>>
>> I don't know about the "A" model, but the "B" easily puts out the 
>> legal limit with my voice characteristics even with that 110 volt 
>> primary.  It does take a good hefty (short) run of #10 for the AC 
>> power if you don't want to see excessive voltage drop.
>>
>> 73
>>
>> Roger (K8RI)
>>> Carl
>>> KM1H
>>>
>>>
>>> ----- Original Message ----- From: "Glen Zook" <gzook at yahoo.com>
>>> To: <hallicrafters at mailman.qth.net>
>>> Sent: Thursday, September 18, 2008 8:31 PM
>>> Subject: [Hallicrafters] Hallicrafters HT-33A
>>>
>>>
>>>> I just obtained a Hallicrafters HT-33A linear with a bad final 
>>>> (PL-172). I believe that there have been some articles on changing 
>>>> out the tube with a more readily available tube.  However, I have 
>>>> been looking on the Internet and just cannot find any.  In this 
>>>> case google is not my friend!
>>>>
>>>> Does anyone have a suggestion as to where I might locate this 
>>>> information?
>>>>
>>>> Glen, K9STH
>>>>
>>>> Website:  http://k9sth.com
>>>>
>>>>
>>>>
>>>> ______________________________________________________________
>>>>
>>>
>>> ______________________________________________________________
>>>
>>
>> ______________________________________________________________
>>
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