[Heathkit] DX-60B Mysteries

[Curt]

My DX-60B when used with an HG-10B stopped working correctly.  The VFO continues to run once keyed, until the DX-60B is put in standby.  It seems that the grid bias line isn't returning to a large enough negative voltage to cutoff the 6CH8.  On further investigation, there is a 20 RMS AC signal on that appears on the bias line when the key is closed, the AC signal continues until the DX-60B is placed in standby.  The NE-2 in the HG-10 is lit with key up, goes out with key closure, and remains off when key is opened.  I'm thinking the AC signal is why it stays off.

The bias supply in the DX-60B has no AC on it.  There is AC at the oscillator and driver bias supply when key is closed, even with both tubes pulled (!?), and the HG-10B unplugged.  All of this behavior is with the DX-60B in Tune ( no plate voltage to the 6146 ).  I just can't figure out what is going on here!  Anyone with a clue?

73, Curt KB5JO