[Elecraft] K3: Keying problem on CAT line

[Fred Jensen]

Hi,

I've been using N1MM logger with the K3 for some time now, using RTS for 
PTT and DTR for keying on the serial line using a USB adapter I got from 
Elecraft.  In the RAC Winter contest, all was going well last night, but 
this AM when I turned things back on, N1MM wouldn't key the radio.  PTT 
is OK, and I can hear the keying in the monitor as a bunch of clicks [at 
the start of each element] I think.  My breakout box indicates that DTR 
is sending real CW keying.  The internal K3 keyer works fine, as does 
the hand key jack, and the radio works normally in all other respects. 
I've tried two other USB-Serial adapters, one of which is totally 
different from the Elecraft version, and they all do the same thing.

Couple of questions:

1.  Does DTR key the radio by going low or high?

2.  Is there some diagnostic thing I can do [maybe via K3 Utility?] to 
pin down the location of the problem?

I dropped off digest mode so I can see individual replies.

Thanks and Merry Christmas to all,

Fred K6DGW
Auburn CA 95603