This tube was called in FU-81 and FU-80.
The Fu-81 is very popular in China, it used in medical equipment now.
And re-manufacture in our city from 2005 or 2006 to now.
73!Hsu
----- Original Message -----
From: "DAVE WHITE" <mausoptik@btinternet.com>
To: "robert briggs" <vk3zl@bigpond.com>
Cc: <amps@contesting.com>
Sent: Sunday, January 25, 2009 7:37 PM
Subject: Re: [Amps] Power transformer...
> Having said that GU81Ms are cheap, I just saw some on ebay for $74 plus
> shipping from Ukraine. Either they've shot up in price or this seller is a
> rip-off.
>
> They're 45 Euros on this site, which seems a bit more like it, but I'll bet
> there are some around for 25 euros at Friedrichshafen this year:
>
> http://www.zeitmann-tubes.com/MilitarySurplus/NosRussianMilitaryTubes/GU81M.htm
>
>
> Slide-in sockets are a bit rarer, though I've seen plenty about over the
> years. Someone may know where to get them, perhaps Andreas DL9USA near
> Berlin? You could always get away with fabricating some clips from finger
> stock, though
>
> cheers
>
> Dave G0OIL
>
> --- On Sun, 25/1/09, DAVE WHITE <mausoptik@btinternet.com> wrote:
> From: DAVE WHITE <mausoptik@btinternet.com>
> Subject: Re: [Amps] Power transformer...
> To: "robert briggs" <vk3zl@bigpond.com>
> Cc: amps@contesting.com
> Date: Sunday, 25 January, 2009, 11:06 AM
>
> Hi Bob
>
> Whatever you're using now certainly puts a decent signal into Europe on
> 160! (thanks for the QSL, by the way)
>
> Personally I'd put the Yaesu transformer on ebay, get something really big
> and use a large tetrode with handles......but that's just me.
>
> Have you thought of a GU43B?
>
> Your HT might be a bit on the low side, because the tube's rated to 3.3kv,
> but it's a 1kw plate dissipation tetrode and is quoted as giving 1.6kW out
> with a plate voltate of 3kv, screen at 350v and anode current of 0.9A.
>
> I bought a box of about 6 of these at Weinheim a few years ago along with a
> few
> sockets, but so far haven't got around to doing anything with them. There
> are usually lots floating around hamfests in Europe.
>
> I guess running it at 2500v on the plate it'd pretty much coast along at
> about 800w-1kw out
>
> I do have a book of all the older military Russian tube data sheets in English
> so can scan the relevant pages and email them to you if you need them.
>
> Maybe also you could try a big glass bottle like a GU81M? These are usually
> dirt cheap. At one time I was going to build a 160m amp with some of these - I
> got them for about DM20 each - but eventually sold them to a local Tesla coil
> builder. Those tubes would go like stink on 160m, they're just a bit on
> the big side physically. One would certainly do the trick for you. According
> to my book, they're quoted as plate voltage up to 3kv at < 6MHz,
> specified as giving greater then 700W out at 2kv plate voltage, screen at
> 600v,
> grid at -200v, grid drive voltage amplitude 300v, min anode current 450mA, max
> grid 1 current 20mA, max screen current 220mA. The lower the frequency, the
> greater the efficiency with this tube (it's a pentode like a big, fat 813)
> but the data sheet doesn't specify the frequency of that spec. There are
> also sites around with some good designs - they're all in Russian but
> Babelfish did a decent translation and I can send
> you the translated copies of the webpages offline if you want them. I also
> have a full datasheet for the GU81M as tranlsated by a Russian lady I knew at
> a
> client's office who allowed herself to be bribed with coffee for a
> translation! - I can also scan and email this if you're interested. I need
> to do this for Hsu in China anyway who subscribes to this list - I've just
> remembered!
>
> cheers Dave G0OIL
>
> --- On Sun, 25/1/09, robert briggs <vk3zl@bigpond.com> wrote:
> From: robert briggs <vk3zl@bigpond.com>
> Subject: [Amps] Power transformer...
> To: amps@contesting.com
> Date: Sunday, 25 January, 2009, 6:41 AM
>
> Hi all....I have just received a power transformer salvaged from a Yaesu
> FL dx2500 linear...I have checked it out and it appears in excellent
> condition....I am about to build another monoband 160 meter CW only
> amplifier and would prefer to use a single tube rather than pairs of
> GI-7BT....I already have two linears with the 7B tubes.....I am
> wondering if this transformer would handle a GS-31B say to 800 watts
> output CW....The primary is 850 volts ac with about 17ohms DC resistance
> through the secondary....According to Yaesu it is rated to 1
> amp...Voltage doubled it would give around 2500volts....I know the 31B
> would only be coasting at this power level and cooling wouldn't be a
> problem..
>
> I do have a second new twin C core transformer which is heavier but it
> was built for running a pair of 813's and has a heavy filament winding,
> useless to me...The secondary also has around 17ohms resistance and
> produces 2900 voltsdc but running a pair of 4/240A tubes it only
> produces around 800 watts CW....
>
> What would be your pick ?? I will build the case large enough to
> accommodate either transformer....
>
> Regards to all.....Bob VK3ZL....
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