[Hallicrafters] Hallicrafters HT-33A

[Charlie]

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
>>>
>>>
>>>
>>> ______________________________________________________________
>>>
>>
>> ______________________________________________________________
>>
>
> ______________________________________________________________
>