[Heathkit] HG-10B/DX-60 Keying question

[Curt]

My HG-10B stopped keying correctly. With DX-60B using a crystal, HG-10B NE-2 
lamp shows -59 VDC in standby and lit. Switch to tune, key transmitter 
causes light to go out, key up and lamp back on.

Using VFO position, -59 VDC in standby and lit. Switch to tune, key 
transmitter, lamp goes out and stays out, VFO continues to run at key up. 
Voltage on NE-02 goes to -76 VDC but NE02 stays off (?!). Switch to standby, 
voltage drops to -59 VDC and lamp turns back on.

Warming up the DX-60B with the HG-10B unplugged, then plugging in the HG-10B 
the NE-02 behaves correctly until the HG-10B has warmed up and the 6CH8 
actually begins to oscillate.  Seems like a tube in the HG-10B?

Both the 6CH8 and 0B2 test ok on my Eico 625, still I am suspecting the 
6CH8.  I haven't found this emission tester to be very good at identifying a 
problem tube unless it is totally dead or shorted.  Unfortunately I don't 
have another 6CH8 to try.

Any ideas would be appreciated.

73, Curt KB5JO