Something I read here many years ago became valuable today.

I have Comcast X1 satellite box in basement. I'm controlling it via MX980 through MRX1. Had a bit of trial and error to get emitter power level tuned. All the sudden it stops working. After a few minutes, realized all that had occurred was turning off light in area where cable box has attached emitter. Sure enough light on and it worked -- light off and nothing. Could not adjust emitter power to satisfy both.

Cut small hole in black electrical tape and adjusted with lights on -- it now works with both. Damn this stuff can be sensitive.

Not sure where I read about tape pin prick method but thanks to all :-)