[Hallicrafters] Re: HT33B and output

[Carl]

That amp really needs to run on 240VAC.

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?

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.

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
> ______________________________________________________________
>