I live nearby one of FU-81's(Chinese GU-81M) maunfacturer, the distance
only 300 mtrs , they made FU-81 in end of 1950s or early 1960s. Stop in
1980s.
all materials /dies are missed . In 1990s , a businessman invest to re-open
the product line , as FU-81's request. New FU-81F quote about $130.
stop in 2007 again.In that time , Russian GU-81M quote only few $$. But
clearly, neither Russian nor Chinese know this information.
They made socket too, quote $35(retail price), new socket.They should have
some new tubes and sockets in stock.
FU-81 mainly use in China Force TYPE62 250W SSB transmitter in end of
1950s. but from 1970s, it widely use in some medical equipment.
73!Hsu
-----原始邮件-----
From: Carl
Sent: Tuesday, February 28, 2012 7:01 AM
To: Hsu
Cc: amps@contesting.com
Subject: Re: [Amps] 833A/GU-48 x4 Amp support
Sockets that cost 2X the tube are ridiculous, especially Russian surplus.
Carl
KM1H
----- Original Message -----
From: "Hsu" <hsu4qro@gmail.com>
To: "Carl" <km1h@jeremy.mv.com>
Cc: <amps@contesting.com>
Sent: Monday, February 27, 2012 5:24 PM
Subject: Re: [Amps] 833A/GU-48 x4 Amp support
> $35 is inexpensive?
>
> -----原始邮件-----
> From: Carl
> Sent: Tuesday, February 28, 2012 5:45 AM
> To: Fuqua, Bill L ; Roger (K8RI) ; amps@contesting.com
> Subject: Re: [Amps] 833A/GU-48 x4 Amp support
>
> Tubes are cheap but not even my son who travels all over Eastern Europe
> cant
> find cheap sockets.
>
> Carl
> KM1H
>
>
> ----- Original Message -----
> From: "Fuqua, Bill L" <wlfuqu00@uky.edu>
> To: "Roger (K8RI)" <k8ri@rogerhalstead.com>; <amps@contesting.com>
> Sent: Monday, February 27, 2012 4:08 PM
> Subject: Re: [Amps] 833A/GU-48 x4 Amp support
>
>
>> My vote is for the GU-81 grounded grid. Looks like folks have been runing
>> them that way.
>> Where can I get some cheap? Sounds like a good project.
>> 73
>> Bill wa4lav
>>
>> ________________________________________
>> From: amps-bounces@contesting.com [amps-bounces@contesting.com] On Behalf
>> Of Roger (K8RI) [k8ri@rogerhalstead.com]
>> Sent: Monday, February 27, 2012 3:34 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] 833A/GU-48 x4 Amp support
>>
>> On 2/27/2012 3:03 AM, Fuqua, Bill L wrote:
>>> I believe he wants 4 glowing plates. Larger the better.
>>> 4x 250th would work but a bit expensive compared to the Russan 833.
>>> I once ran 2x 250th in grounded grid driven by a pair of 6146Bs on 20
>>> meters.
>>> So 4 should work.
>>
>> The GU-81 is, or was, very popular in Europe, particularly running a
>> pair of them. I think you'll find it's a Pentode, not a Tetrode. Of
>> course it still requires the same power supplies as a Tetrode as the
>> suppressor is grounded. They are rated to 50 Mhz but at substantially
>> reduced power. Dr Alex http://www.nd2x.net/ur4ll.html lists a pair of
>> them running 3KW without forced air.
>> http://www.nd2x.net/ur4ll/gu81-skem.gif Nice thing about them is they
>> can be run without forced air. Other than the two connectors on top, to
>> me they don't look much like an 833. The audio guys have pushed the
>> price of 833s well out of reason as far as I'm concerned.
>>
>> I should have picked a few more up when they were running less than
>> $20USD each. The ones I purchased were $18 each. Now they are averaging
>> more than twice that and the sockets are running close to $50 each.
>> (Prices vary widely) I've often thought I'd like to build monobanders
>> for 160, 75, and 40. *Apparently* they are a tube that can be "abused"
>> and run well beyond its official ratings. I have no idea as to it's IM
>> characteristics, but I did hear a couple groups using a pair of them as
>> drivers. <:-))
>>
>> OTOH getting four of the rather massive graphite plates to run a
>> substantial glow might be pushing a fair amount of power out.
>>
>>
>> 73
>>
>> Roger (K8RI)
>>>
>>> 73
>>> Bill wa4lav
>>
>>
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