Home Projects Tubes   500w 4X150A/7034 Tube 26-30MHz VHF output amplifier

 

 

500w 4X150A/7034 Tube 26-30MHz VHF output amplifier

 

 

The more information about tube 7034 can be found at this address http://www.g8wrb.org/data/Svetlana/pdf/4X150A.pdf Shortly: The heater voltage 6v 2.6Amp. You can see the yellow light in it. All metal/ceramic construction. First apply the 6v heater voltage 30 second before the anod voltage. Sufficient cooling must be provided for the anode. The best is to use an anode chimney. Air-flow is in the base-to anode direction.

Use  20-cm wire for coil L2.  L1 and  L3 similar bobbins . If it is not a good dummy load use a bulb 220v 150w. C9 and C10 high voltage vacuum-dielectric, air-gap capacitors. Otherwise plastic variable capacitors easily will melt in a short time. The main different at this device from the others is the coil L2 and the  capacitor C1. Coil L2 increases the power and also audio modulations. Use C1 like a gain control unit. More gain can cause parasitic oscillations.  Don't exceed the power limit. The limit is the place what begins a small arching  on  tube'g1. And you may hear a small ugly sound. Don't wait, decrease the power immediately. Otherwise the tube can easily be damaged forever. Always stay at under the maximum power. If you feel no gain increasing, insert the opposite terminal of coil L2

You see this amplifier is a special grounded grid configuration. This makes the 7034 a little harder to drive.  If it is no a good dummy load use a bulb 220v 150w.  C11 not a main factor at this device, but it makes some gain control too. Short-cut the leads if you want. This can cause some power decreasing. R1 is interested in receiver. It prevents unexpected parasitic signal to go in.

WARNING!  DON'T BUILT THIS DEVICE, IF YOU ARE NOT AUTHORIZED,  OR QUALIFIED PERSON,  ALL DANGERS

BY LAW AND THE LETHAL HIGH VOLTAGE

 

 

 
 

 

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