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GU39B-1

wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,404
1,268
173
Any one ever seen any schematics or info on this Russian made transmitting tube?

I did find the spec sheet.

Looking for schematics and info on using it in GG if it can be done.

thanks
 

Johnnybgood

New Member
Nov 15, 2013
40
1
8
Hope you got a beefy psu to power that tube ? I would rather get a QY5-500...HI or a pair of them.

GU39B-1
Type tetrode
Cathode type tugsten,carbidized,direct heating
Application field power amplification in SW transmitters
Brief application amplification
Envelope glass to metall
Cooling method forced air
Dimensions 293mmx128mm
Mass 8 kg
Filament voltage 6.3 V
Filament current 85 - 105 A
Mutual conductance 20 to 28 mA/V
Gain coefficient 6 to 9
Output power 8 kW
Maximum anode voltage 12 kV
Maximum operating frequency 30 MHz
 

wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,404
1,268
173
Got a pole pig, power transformer, also have all the bias ps it is basically built per say.

Previous owner stopped on the project and sold it

Where he found that 6.3v 150 amp filament tr I have no idea but it is a monster.


In GG if it can be done the filament choke would be a monster to handle the amperage.
 

Crusher

Well-Known Member
May 12, 2007
838
370
73
LOL. At that point, operator may as well run a 3cx10,000a7 and be done. If its the tube I am thinking of, good luck finding a socket. But I will say, it is cheap. Think I seen one on ebay awhile back, around $300.
 

wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,404
1,268
173
LOL. At that point, operator may as well run a 3cx10,000a7 and be done. If its the tube I am thinking of, good luck finding a socket. But I will say, it is cheap. Think I seen one on ebay awhile back, around $300.

I have the socket have all but it is in a tetrode arramgement, and of course most of it is burned up.

Previous builder had issues with it.

so it fell into my shop and I am looking at trying it in GG.
 

Johnnybgood

New Member
Nov 15, 2013
40
1
8
The big issue will be to have adequate control measures in place to stop it taking off and also to shut it down when a problem occurs. Best bet is to try and find another op using that tube and gleem some info from them on how they control it.
 

Shockwave

Sr. Member
Sep 19, 2009
3,780
3,280
273
That tube is going to require a good deal of drive if it can be run in grounded grid. Some tetrodes do not like this and can have problems with the screen grid over dissipating. It's more common in smaller tubes like the 4CX250B even though there are people running them in GG. The best thing you can do is figure out what's wrong with the existing circuit since the basic supplies for tetrode operation are there.

Tetrodes burn up different sh*t for different reasons and the symptoms it demonstrated just before it let the smoke out can tell you allot. Did it pass the DC bias tests? Can you apply all supply voltages and confirm it's in cutoff during RX and properly biased during TX? Did it ever make RF output? Did it suddenly take off and show excessive output just before the failure or a slow steady climb in output?

If it doesn't bias, remove the tube and plate voltage and test at the socket to find the incorrect voltage. If output slowly climbed until failure, you have a weak screen supply that either needs much more resistive loading to handle the negative screen current or the better approach of shunt regulation. Shunt regulators for any voltage can easily be made from common high power NPN transistors with a zener diode across the base collector terminals. Series as many as needed to reach your voltage.

Instant and severe power increases are related to oscillations within the amp. The tube should have a VHF parasitic suppressor in the RF path either in the plate circuit or control grid circuit. The screen grid MUST be well bypassed to RF ground. Four, 500 pf doorknobs equally spaced around the screen ring with high voltage .01 uf ceramic disks across each doorknob does the trick. Neutralization will be 100% required on this tube and is NOT optional. The construction of the tube with long internal leads and a maximum frequency of 30 Mhz. will oscillate for sure without neutralization.

The input circuit should be a parallel tuned type raised slightly above RF ground. Using a capacitor around 470 pf to provide this ground path will keep it slightly off RF ground and allow an easy place to inject the neutralization signal where it will get the needed 180 degree phase inversion. You don't need to purchase expensive neutralizing caps either. You can make your own adjustable cap easily enough.

Just poke a hole through the RF deck close to the anode where you can put a grommet and copper wire through. Keep enough distance to prevent arcing to the plate. About 1.5 inches will work at this plate voltage. How much wire you push through the grommet will control the capacitance. "Care and feeding of power grid tubes" by Eimac outlines a simple cold test procedure for neutralizing.

If you don't have the test equipment they mention, replace the RF generator with a radio turned down to just under 1 watt. The sensitive RF detector can be a cheap field strength meter. Pull the antenna off it and attach coax. The center wire to where the antenna was and solder the braid to the metal case. Place a 47 ohm carbon resistor across the center wire and braid to load the meter too.

Special consideration to glitch resistors should be used with tetrodes. The plate glitch MUST be able to handle the full brunt of that pole pig in a fault condition WITHOUT opening up. If it opens, an arc will form across the open and allow full current to flow just long enough to do damage. Then to add insult to injury, the open plate supply will now force the screen grid to over dissipate into rapid self destruction.

The screen should also have a glitch resistor. That can be a simple 47 to 100 ohm 2 watt carbon. If it opens, the tube will be cutoff. Using an MOV on the screen terminal of the socket will prevent the screen from ever reaching the voltage where it could arc internally.
 
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wavrider

W9WDX Amateur Radio Club Member
Jun 2, 2009
3,404
1,268
173
Shockwave,

Thanks for the input and construction hints.

The previous owner/builder said it did work on 20 meters??

I dunno was not there and do not know the guy.

I will have to reverse engineer what he has built, no schematics per say,then repair/rebuild what is necessary to get it back up and running.

Should be an interesting project.
 

Shockwave

Sr. Member
Sep 19, 2009
3,780
3,280
273
That will drop a good deal of the RF drive right across the filament transformer. Making the secondary leads radiate RF including the bias center tap that could cause RF to get into the bias circuit. The unchoked transformer secondary will also place additional loading on the cathode circuit. Making it more difficult to drive the lower impedance.

I have seen examples where well over 100 amps was choked using about 6 inches of #43 ferrite beads on each lead close to the tube and good RF bypassing caps on the transformer side of the choke. In the absence of any screen voltage most tetrodes will have lower gain than a hi mu triode for the same application. They usually function more like a medium mu triode and would struggle to reach 10db of gain.
 

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