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Author Topic: Russian Tetrodes  (Read 5039 times)
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KD1SH
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« on: September 24, 2020, 12:11:50 PM »

  Anyone have any experience with the Rusky tetrodes like the GU-84B? As far as transmitting tube prices go, they're practically giving these things away with Happy Meals. 2500 watt plate diss; obviously few us will ever own mod iron to fully utilize such a beast, but you could screen modulate that tube and still get a kilowatt carrier. Not that any of us legal hams would ever do that, of course, but it's fun to fantasize. Svetlana 4CX-400's are cheaper than dirt, too.
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« Reply #1 on: September 28, 2020, 04:24:10 PM »

Where are you finding these Russian bargains and are there sources for the sockets as well?

Phil
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KD1SH
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« Reply #2 on: September 28, 2020, 04:44:16 PM »

https://qro-parts.com/

Where are you finding these Russian bargains and are there sources for the sockets as well?

Phil
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KD1SH
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« Reply #3 on: September 28, 2020, 04:57:06 PM »

Only $99.50 for the 4CX-400A, and I think they can use the same sockets as the 4CX-250 series.
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KC4VWU
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« Reply #4 on: September 29, 2020, 08:36:18 AM »

I picked up a few of the GI-21b triodes for a rainy day project in the future. Might be a good conversion for a junker Viking I that's been sitting here a while. They are a coaxially mounted type, but a planar socket modifies nicely to fit. They're Cheeeeep too! Now all I need to do is find that round tuit.
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KC2ZFA
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« Reply #5 on: September 29, 2020, 09:27:47 AM »

is there any class C info on the 4cx400a ? seems there痴 only
Svetlana data out there. Searched for eimac data but zip, the
400a is apparently a totally ruskie tube.
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KD6VXI
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« Reply #6 on: September 29, 2020, 11:37:06 AM »

Be wary of the Russian (Svetlana to be more exact) ratings.

The "4CX800"......  That was a rebadged tube that Daughters (IIRC) imported as he was the American contact for Svetlana.

Once the data sheet was properly translated, it was fou d that it's a 600 Watt PDiss tube.

Run as such, all the short failures inside the tube magically stopped happening NEAR as much.

The Russian tubes are pretty hot, as far as gain and peak emissions go. But they don't last long like that.

I've built quite a few Russian tube amps over the years.  Run sanely, they are a great deal.  But they are no Eimac tube!  Nor Amperex.. 

If you build something out of one, buy a pair, so you have a spare.  Stocks are depleting and once they are gone....  Ask the people who bought original Emtrons what they had to do.....

--Shane
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KD1SH
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« Reply #7 on: September 29, 2020, 12:00:18 PM »

I've heard likewise about the GU-84/4CX-2500A - more like 1600 watt plate dissipation than 2500.


Be wary of the Russian (Svetlana to be more exact) ratings.

The "4CX800"......  That was a rebadged tube that Daughters (IIRC) imported as he was the American contact for Svetlana.

Once the data sheet was properly translated, it was fou d that it's a 600 Watt PDiss tube.

Run as such, all the short failures inside the tube magically stopped happening NEAR as much.

The Russian tubes are pretty hot, as far as gain and peak emissions go. But they don't last long like that.

I've built quite a few Russian tube amps over the years.  Run sanely, they are a great deal.  But they are no Eimac tube!  Nor Amperex.. 

If you build something out of one, buy a pair, so you have a spare.  Stocks are depleting and once they are gone....  Ask the people who bought original Emtrons what they had to do.....

--Shane
KD6VXI
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K1JJ
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« Reply #8 on: September 29, 2020, 12:24:53 PM »

If you can find one, an Eimac YC-156 or YC-179 is probably the cleanest linear tube out there. There were a lot of MRI pulls around at one time.  5 KW plate dissipation and the filament is indirectly heated pulling only 15 V @15A = 225 watts.

https://www.wv7u.com/yc156amp/qa/YC156DATA.pdf

Simple GG triode.  This tube is worth looking and waiting for if you're gonna build a big, clean linear amp.

T
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KD1SH
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« Reply #9 on: September 29, 2020, 01:21:48 PM »

After around a year of soul searching, I'm starting to lean in that direction.
I love glass tubes, but the bigger ones are getting harder and harder to find, and most new ones are made in China. Likewise glass chimneys and air-system sockets.
The Russian tubes: cheap but specs are often over-promised.
Tetrodes have nice gain, but are electrically more fragile and require more careful tuning and monitoring of screen current.
Nothing like a big, rugged, grounded grid triode.
Only issue with the MRI tubes is that new ones are unaffordium for any of us; we have to buy pulls. But how many of us will even come close to taxing a tube like that?


If you can find one, an Eimac YC-156 or YC-179 is probably the cleanest linear tube out there. There were a lot of MRI pulls around at one time.  5 KW plate dissipation and the filament is indirectly heated pulling only 15 V @15A = 225 watts.

https://www.wv7u.com/yc156amp/qa/YC156DATA.pdf

This tube is worth looking and waiting for if you're gonna build a big, clean linear amp.

T

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« Reply #10 on: September 29, 2020, 03:03:13 PM »

Yep, no socket needed, -30 V grid bias in the form of a string of diodes in the cathode.   Pulls are usually very FB cuz they are replaced by the number of hours run.   15 V fil.  Big emission.     3-4KV is a good voltage for ham use and you're on the air.  Run it lower power and the IMD is even cleaner. I have measured upwards of -45 to -50 dB  3rd order.   No need to beat it with the recommended 5-6KV.   They are like an 8877 in many ways but four times the dissipation.  Amplification factor of 200.

My favorite tube for QRO linear use by far.  They are the pinnacle of power grid design, used in refined MRI machines. They will probably stay at the top since everything has gone solid state since.

** Important point:  Because the anode and fin spacing is so big, the air runs very quiet thru the tube compared to smaller tubes. Compare it to a 4CX-250 in a mil rig and it is amazing. A big, slow blower mounted on the back of a small  sub-chassis is the quietest and most efficient way to go -  other than a remote system.

T
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« Reply #11 on: September 29, 2020, 03:32:07 PM »

The yc156 is a 3cx15000 internals with a 5kw cooler.

Great tube, but nowhere near the affordable end they where years ago.

The socket less 3cx6k and 3cx3k are also great tubes.

Then of course, there are guys running things like this....

This is a 3x10 for 160 recently pulled from an SK contesting station.  Guess he wanted 100 pct duty cycle am.

--Shane
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« Reply #12 on: September 30, 2020, 01:39:23 PM »

"Put a brick on the key and go on vacation" type of amp.

Too bad QRO doens't acept bitcoin.
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