Ok.. Since the only difference between the extender and the connector inside the mainframe is “Option 12” connected to pins 27A’s and 28A’s, I removed all the 6 coax from the back of the connectors to the 6 BNC’s at the back of the unit.
Everything behaves as expected... Baffling to me...
Now I can turn my attention to the DC505A which is counting gibberish if at all, and to the DC503 that, all of a sudden, just stopped counting altogether. Then I’ll turn my attention to the SC502 that came with the TM506.
Thinking out loud: I guess this is what you have to go through when you buy a lot of things at the same time....
A lot of troubleshooting!!
A big thank you to ALL of you for bearing with me.