[Hallicrafters] Re: HT33B and output

[David C. Hallam]

There was an article published in the June 1961 QST "Understanding Tetrode
Screen Current"  by David D. Meacham W6EMD and included in the 4th edition
of the ARRL handbook "Single Sideband for the Radio Amateur".  It explains
the reading of the screen current meter of a RF amplifier and how to tune
one for proper operation.

It should be required reading for anyone with a grid driven tetrode or
pentode linear.

David
KC2JD/4

> -----Original Message-----
> From: hallicrafters-bounces at mailman.qth.net
> [mailto:hallicrafters-bounces at mailman.qth.net]On Behalf Of Carl
> Sent: Saturday, September 20, 2008 9:47 AM
> To: Mark Shaum; hallicrafters at mailman.qth.net
> Subject: Re: [Hallicrafters] Re: HT33B and output
>
>
> 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
> > ______________________________________________________________
> >
>
> ______________________________________________________________
>
>
>
>