[Hallicrafters] Re: HT33B and output

[Roger (K8RI)]

Carl wrote:
> That amp really needs to run on 240VAC.

Amen!
As it is fully capable of running the legal limit that is a 
heap-and-a-bunch of current through that Rhomex.
>
> Ive been running the antique 3500VAC @ 1.2A (175 Lbs !!) transformer 
> in my vintage AM station off a 5KVA 240/120; 220/440 transformer I 
> found at a surplus electrical shop for $40.
>
> Since there are already several dedicated 240V lines wired into the 
> basement shack I wasnt about to mess with adding a 120V run of #8.
>
> 1200W out is what is the norm for a 2000W PEP input amp of the 60's.
>
> The PL-172 seems to be rather fragile or is it something to do with 
> the HT-33A design? Or cockpit era?
>
I think it's more the problem you mention below. That and the PL172 does 
have a tendency to go gassy with that glass to metal seal. Then the guys 
that have spares put them on the "unused" shelf so they can say they've 
never been used.  Those things should be cooked for an hour or two every 
few months, or at least twice a year.  The straight 8295A is much 
better, but still not immune to just setting around.

If you can beat them as hard as I have they must be a reasonably good tube.

> My long experience with the National NCL-2000, from the initial design 
> to present, convinced me that most hams are incompetent to run a grid 
> driven tetrode. Trying to teach them to use the screen current as a 
> tuning indicator and ignore the plate meter usually resulted in glassy 
> eyed stares! I  have 1967 date code tubes in the one I use with the 
> HT-32B and SX-115 and it still puts out almost 1200W.
>

73

Roger (K8RI)

> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Mark Shaum" <k9tr at dtnspeed.net>
> To: <hallicrafters at mailman.qth.net>
> Sent: Friday, September 19, 2008 10:43 PM
> Subject: [Hallicrafters] Re: HT33B and output
>
>
>>> From: Glen Zook <gzook at yahoo.com>
>>> Subject: Re: [Hallicrafters] Hallicrafters HT-33A
>>
>> On my 33A, the best of my three used PL-172's would manage about 900 
>> to 1000 peak watts output, measured on 40 meters as I recall.  I 
>> picked up a NOS 8295A and that output jumped up to 1200 watts.  If 
>> you want to maximize the potential of the amp you will need to add 
>> some positive suppressor grid voltage.  I kludged in a bypass 
>> capacitor ring and with 75 volts on the suppressor grid output went 
>> easily over 1500 watts with no other changes. The tube manuals will 
>> indicate the recommended suppressor grid voltage.  I returned mine to 
>> ground as I didn't want to overstress anything else in this fine 
>> hernia generator of an amp.  And you better have a stiff 120V supply, 
>> with the added output I was popping the internal 22 amp breaker on CW 
>> tests.
>>
>> Mark K9TR
>> ______________________________________________________________
>>
>
> ______________________________________________________________
>