[Hallicrafters] Prices of Hallicrafters gear

Tue Jun 6 12:10:23 EDT 2006

> At 11:50 PM 6/5/2006, you wrote:
>>Hallicrafters HT 33A amplifier, less PL 172 tube,
>
> John,
>
> Please be seated.
>
> If you look for new PL-172's you will find prices in the $800 each range. 
> Most likely, they will have been made in Russia or some such place, and 
> likely will perform just fine.

I don't believe the Russians ever made an equivelant for the PL172/8295A or 
that there are any new manufactured PL172s or 8295A tubes available.  They 
did make a 5CX something but as I recall the physical dimensions were 
different than the PL-172.

>
> Some years ago, I had a chance to buy an HT-33 at a hamfest. It seemed as 
> if I could have had it for around $300. I passed it up because they weigh 
> well over a hundred pounds, and my car was a long way off. I'm now glad I 
> did not buy it.
>
> The "PL", of course, means Pent Labs, the originator of the tube type and 
> apparently the only manufacturer of it at that time.  At:
> http://www.eham.net/classifieds/detail/171141
> I find an ad from a year ago offering a new Penta Lab tube for $375.
>
The new tubes are usually refer to New NOS or New Old Stock. IOW they are 
presumeably unused original PL172s.

> At contesting dot com,
> http://lists.contesting.com/pipermail/amps/1998-August/006091.html
> I find a discussion about alternate tube type number (PL-8295 ), and 
> mention that it was used only in the HT-33. This is not quite true, 
> because

You need to be careful here. Is this an HT33, HT33A, or HT33B?  The HT33 
uses a pair of 4CX-300s as I recall.  It's a tall, skinny, bayonet base tube 
and a pair run about half the power of the 33A and B which use the PL-172.

If you look at a PL172 it will have the numbers 8295 stamped on it after the 
PL-172.  IOW they are the same tube.  There is an 8295A which is a metal 
ceramic version of the same tube.
With both the amp and the tube the suffix is important.

> the TMC company used it in one or two of their transmitters (the PAL-1K, 
> perhaps, and the driver section of their 10 kw transmitter).  This poster 
> mentions that there are "west coast dealers" who can sell you new or 
> tested used tubes.  He goes on to comment on possibly converting the amp 
> to

Radio Parts has, or did have both the PL-172 and 8295A for sale guranteed to 
be good. IOW if it's gassy you send it back, but like all things there is a 
price. The last time I checed they were out of both tubes. Previously they 
were getting around $1,200 USD for the PL172 and twice that for the 8295A.

The PL:-172 is glass and metal while the 8295A is ceramic and metal.  If 
they haven't been used the PL-172s tend to get gassy which is usually not a 
problem with the 8295A.  There are quite a few of the PL-172s out there and 
it's not unusual fot find them for $300 or less, but many tend to be gassy 
which is why the guranteed ones are so expensive.

> another tube: "The conversion is quite the job requiring a new socket and 
> tube. What your doing is just using the shell and ps for another amplifier 
> you design into the cab (-inet)."
> He quite rightly indicates that you are undertaking the design of a new

Maybe so and maybe not. If you put a tube in there running the same plate 
voltage and current then the tank circuit is fine as is. The grid circuit is 
what they call "swamped grid" or just a dummy load wrapped around the socket 
with the voltage used to drive the grid.  There is a good chance the grid 
bias and screen voltage will need to be changed as well as the filament 
voltage.  I see the conversion (depending on the tube) as more one requiring 
complex and quite possibly difficult, mechanical changes rather than 
electrical.

However the biggest problem is the size and mechanical design of the 
PL-172/8295.  It's larger in diameter than today's standard tubes and uses a 
very coarse fin structure allowing the tube to be cooled using a normal fan 
blowing up through and around the socket.  Although it'd take a new socket 
and chimney the 4CX1600B would make a good replacement with the exception of 
cooling. The 4CX1600B takes more air and at a higher back pressure that is 
unlikely to be within the capabilities of the fan under the socket. OTOH if 
you can find the space a muffin fan used to pressurize the tube socket 
compartment should work. It also might be possible to add a squirrel cage 
blower to the side of that compartment. Of course that would be a dead 
giveaway as to being modified.

The stock chimney is large enough that a spacer ring could be added at the 
top and a ring of silicon rubber forming a tube (as in the Alpha 76) for a 
chimney inside a chimney helping to keep the stock look.

> amplifier if you change tubes.  This is not for the faint of heart or for 
> the beginner in RF amplifier design, construction, and testing.
>
>>SR 500 Tornado transceiver WITHOUT power supply.
>
> You are in a similar situation with trying to build a power supply. I am 
> not familiar with the Tornado, but I would expect that building a supply 
> for it would be much simpler than converting the HT-33 to a different 
> tube.
>
The PS 150 is a simple design and I believe the one for the SR500 is just a 
heavier version.

> In the case of the TMC PAL-350 that I have one of without supply, there is 
> a lot of important function lodged in the supply.  Plate and screen over 
> current protection, bias supply, supply voltage switching for different

As I recall there is no over protection in the power supplies for the SR 
series with the possible exception of the SR2000

> modes,  and warm-up time delay are some I can think of.  The PAL-350 
> supply

Nor any delay circuitry with the possible exception of the SR2000.

> *looks* simple enough from the front, but there is a lot of stuff in 
> there.
>
>>  Electrical condition unknown and being sold "as is".
>
> If I were considering these radios, I would decide on my dollar offer from 
> the attitude that I was buying a collection of spare parts in the case of 
> the HT-33, and an interesting challenge in the case of the Tornado.  Note 
> that AES wants $81 each for the 8236  tubes but is out of stock!  (Does it 
> use four of them?)

Two.

73

Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com
>
> I hope these thoughts help you in deciding what to do.
>
> Roy
>
> - Roy Morgan, K1LKY since 1959 - Keep 'em Glowing!
> 7130 Panorama Drive, Derwood MD 20855
> Home: 301-330-8828 Cell 301-928-7794
> Work: Voice: 301-975-3254,  Fax: 301-948-6213
> roy.morgan at nist.gov --
>
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