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Full Version: HEATHKIT SG-8 SIGNAL GENERATOR unknown mod?
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I have a heathkit sg-8 that some one has modified
They put a 8 pin socket on the right upper side.

Pin 5  goes to pin 1 of the 12AU7
Pin 6  goes to RF out jack
Pin 7  goes to ground 
Pin 8  goes to 6.3 Vac 

I ask to find out if any knows of this mod?
 If so what tube should I get?
My guess is this tube is amplifying the RF.
This is the front of the SG-8
This is the back
I doubt it's a socket for an additional tube, probably for some sort of accessory. Maybe an 100kc calibrator.
With the signal gen  hooked up you could monitor rf plate voltage on the 12AU7 and filaments for stability?
HEATHKIT SG-8 now up and going