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[Amps] 4cx1500b amp conversion

Subject: [Amps] 4cx1500b amp conversion
From: Felipe Ceglia - PY1NB <>
Date: Mon, 27 Aug 2007 08:10:08 +0000
List-post: <>
Hello fellows,

I am finishing the process of converting an JRC NAF-521 HF amplifier, 
which originally came with a pair of 8122  to use a 4cx1500b tube.

It seems like it is self-oscilating on VHF frequencies as the anti 
parasitic choke got hot, and the resistors even got unsoldered with heat.

It is in grid driven configuration, and I am wondering about putting it 
to a grounded-grid configuration, but in other hand I would not feel 
very good about it, as I already have in hands a nice power supply to 
run it from.

You may see the tube part of its diagram and rf deck photos at:

Would you suggest anything, another configuration?

73 and thank you,

Felipe - PY1NB
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