[Hallicrafters] Hallicrafters HT-33A

[Carl]

And the 3CX1000A7 requires 30A. I included those in the list as the 
quick heating tubes are desirable to some and they are also almost 
impossible to hurt. I use the 3CX1000A7 in HB 144 and 222 mHz 1500W amps 
and they are like the Energizer Bunny.

There is also something to be said for triodes in the low IMD 
department. And the 8877 socket is simple and cheap compared to the 
rest. If you keep the output within reason a good muffin fan should 
provide sufficient cooling.  The early DTR-2000 used that method and 
went to a regular blower later due to the horizontal tube and excessive 
back pressure. Use a thermal switch in the output air to control a Hi-Lo 
speed.

To get the best IMD out of the multi grid tubes the grid and screen 
supplies must be regulated and the simplistic route of VR tubes or 
zeners isnt sufficient for that. G3SEK offers a nice regulator board and 
its available thru Down East Microwave in the USA. Ive used the board in 
retrofits of several commercial tetrode amps and the A/B results on the 
spectrum analyzer are very impressive.

Triodes will also require a tuned input. Luckily there are relay 
controlled assemblies available that can either be fitted somewhere 
inside or mounted externally. You will need some way to switch them with 
12VDC.

Since the HT-33 series will arguably never attain cult status a well 
crafted update will probably add to its value.

Carl
KM1H



----- Original Message ----- 
From: "David C. Hallam" <dhallam at rapidsys.com>
To: "Carl" <km1h at jeremy.mv.com>; <gzook at yahoo.com>; 
<hallicrafters at mailman.qth.net>
Sent: Friday, September 19, 2008 7:27 AM
Subject: RE: [Hallicrafters] Hallicrafters HT-33A


> While the 4CX1500A and 5CX1500A are excellent tubes and rugged as 
> hell, they
> have one draw back.  They require 40 amps for the filament.  I have a 
> HB
> linear with a 4CX1500A running grid driven like the HT-33A.
>
> David
> KC2JD/4
>
>> -----Original Message-----
>> From: hallicrafters-bounces at mailman.qth.net
>> [mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Carl
>> Sent: Thursday, September 18, 2008 10:08 PM
>> To: gzook at yahoo.com; hallicrafters at mailman.qth.net
>> Subject: Re: [Hallicrafters] Hallicrafters HT-33A
>>
>>
>> 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.
>>
>> 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
>> >
>> >
>> >
>> > ______________________________________________________________
>> >
>>
>> ______________________________________________________________
>>
>>
>>
>>
>
>
>