@ Poita: I glanced through the X9 service manual and it seems to have the same test point as the 5xx-6xx laserdisc players located on the main board. It should be labeled CN106. It has 11 pins. Pin 3 should be RF out and pin 8 is GND. Here’s a few pictures of my modded s315. It should be just about the same procedure for you to tap your x9. BTW, the test point probably terminates at 50 ohms so you can use a normal BNC connector and 50 ohm coax for all of the connections.

The housing I used is a 10 pin AMP MOD II housing with 2.54mm pitch and AWG 26-22 pin connectors…