[Elecraft] KAT500 ANT1 problem

[Andy Durbin]

"The secondary toroid of the directional coupler has a direct path to ground. That means there is no straight-through DC path."

I may have misunderstood the schematics.  What I see is a DC path between J1 input and "ATU".  If K20, K21 and K18 are all in the NC state there will be a low impedance DC path between "ATU" and ANT-1.  If any of these relays is faulty and not closed the DC path will be open.  Sure, there is a DC path between J1 and ground through the coupler but I don't see how that changes the path to ANT-1.

If ANT-1 is open circuit to XMTR isn't it likely that K18, K21, or K20 is faulty?

I realize this is now just a mental challenge as the OP's problem has already been solved.

73,
Andy, k3wyc