We were tying to prep for Nellis and had an aircraft where rudder kept failing BIT test, PCU and fairy kit had been to the bay several times, hyd bay test set even used on the aircraft and it passed. I was new ( but the chief and had heard of some incompatibility problems). As the jet had to go I made the guys rob a PCU from another aircraft and it worked OK, we then took the PCU that we had removed and fitted it to the robbed aircraft and that worked OK as well ..... bloody electronics. I also made myself unpopular in Goose bay a ‘leccie’ came to me with a popping circuit breaker he thought it was a bit of ‘rigger kit’ that was causing it but he did not know what it was and the riggers he was showing did not understand ‘electric string’, fortunately I loved the stuff so he and the new boy went to look. 15 mins later returned with the news that it was a duff solenoid on the HLWSCU and it could not be replaced in situ. Suddenly no one wanted to believe the new guy!, even when I showed the guys that electrically disconnecting just that one solenoid stopped the CB popping one of them still wanted to try the e box fist ..,..just in case.