I have had my X-10 stuff working for years with no issues. I use house codes A, B, & C. I control lights, arm/disarm alarm system, and the garage door/gate. A week or so ago, I left arming and returned, disarmed the alarm, an hour or so later started to leave and it wouldn't arm. After some checking realized that nothing worked. No new items or changes have been made. After some checking I found that if I disconnected the bridge (coil & cap) A-10 & A11 worked but nothing else.
Any ideas or suggestions, I don't have any test equip. I have the TM751 & RR 501s. Using HR12As and SS13As, I have lamp modules and wall switches. I can make the TM751 or RR501 "click" as unit 1, but no signal is transmitted to a module even when plugged into the same strip.