[GreenKeys] ST6 not spacing?

[Eugene Hertz]

Hello all! I am hoping this is a real quick fix. My brother in law is coming to visit in about 1 hour and he's never seen my shack (they live in iowa, I am in new york).  I am dying to show him the M28ASR/KSRs in action. For some reason my ST6 decided not to work. It had been working great on the bench for several weeks (and several years prior to that).

Problem seems to be I cannot get a space out of it. It is in constant mark state.  Even though the standby light goes out when a signal comes in (as it should).  I drive 2125 and 2295 into it, the meter shows peaking (when I sweep) but I cannot get the loop current to space.  

In an attempt to trouble shoot, I have removed all boards except 1-170, 2-170, lp/keyer and the power supply. I have also swapped all of these boards with other that I have that are known to work (or at least were known to work as of 2 weeks go. 

What could I possibly be doing wrong here? One thing I will note is that my receive lamp seems to be out.  Could someone tell me if my space lamp were broken for some reason, could this prevent the loop from spacing?

Any suggestions welcome. 
thanks
Eugene