I did the same thing to one of the Heath LMO's, just shoved the FET leads right into the correct tube socket contacts, applied +12vdc to the B+ input on the LMO and it worked great! very stable!! (but no glow
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I have a VF1 here that someone had solidstated using a mpf 102 ( I might have the FET letters mixed up). I did not use the voltage divider network or power from a rig but used an 18 volt wall wart ( transformer ) with extra filtering and it works great. Max drift about 50 cycles. The dope on this was in an old QST but I don't know what year.I'm going to do another one just for the fun of it.
73