[Amps] Power transformer...

Sun Jan 25 09:11:54 EST 2009

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 at btinternet.com>
To: "robert briggs" <vk3zl at bigpond.com>
Cc: <amps at 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 at btinternet.com> wrote:
> From: DAVE WHITE <mausoptik at btinternet.com>
> Subject: Re: [Amps] Power transformer...
> To: "robert briggs" <vk3zl at bigpond.com>
> Cc: amps at 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 at bigpond.com> wrote:
> From: robert briggs <vk3zl at bigpond.com>
> Subject: [Amps] Power transformer...
> To: amps at 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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