[AMRadio] GK500 OTA almost


Don Rasmussen don.kd2fo at gmail.com
Thu Jan 5 22:21:56 EST 2017


I believe you may need to NEUTRALIZE the final.     Any grid driven Class C
final will need to be neutralized.     Sometimes you can avoid
re-neutralizing going to new final , but maybe not.

To neutralize you need to REMOVE BOTH PLATE & SCREEN VOLTAGE.....then
listen with a sensitive device coupled to the GK-500 plate circuit, while
applying normal grid drive.....up o the 10 or 15 meter band.      There is
a neutralizing capacitor which should be tuned for MINIMUM RF
"FEED-THROUGH"​ on your sensitive device (i.e. rcvr s-meter reading)
coupled to the temporarily disable RF plate circuit.

When the procedure is finished , re-connect both PLATE and SCREEN vooltages
to the tube for normal operation.

CAUTION.....IF PLATE VOLTAGE IS REMOVED WITHOUT DISCONNECTING SCREEN
VOLTAGE.....YOU WILL BURN UP THE SCREEN INSTANTLY.

I am the owner of a GK-500A (currently running a 4-400A) and you have my
opinion.....even if there is some other issue, for best NON-OSCILLATING
operation of the final.....it SHOULD BE NEUTRALIZED.      A badly out of
neutralization final will OSCILLATE.....it sounds like this is possibly
your problem.

73, Don KD2FO


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