Trouble shooting an E.S.C.

I was flying the Cardinal and didn't get too far when the motor quit. I didn't know if the battery was dead or some other part had failed. I installed another battery and it flew like normal which pointed me towards the battery. I flew another battery and it worked normal. At home I checked the remaining voltage in the suspect battery and it was about what i figured it should be given the short flight. I installed a forth battery and ran it on the ground. It didn't even start this time which now points me towards the electronic speed controller or E.S.C. I had a new one and installed it on the plane and ran it for a minute and it worked fine. The next day I went to the park and got in 4 flights with the new parts and everything worke perfectly. Back at home I removed the shrink wrap from the suspect E.S.C. and gave it a 5X inspection. I found what looked like some dirt of some kind on one of the processor connections. I cleaned it off and installed the E.S.C. back on the test mule plane. At the field I lew it 4 times with no problems. I'll keep testing it more before trusting it on a more important plane. I did order another new one from Brodak. At the field today I got in more flights with the suspect E.S.C. and a quirk with the timer bugged me. It ads power in several stages during the flight. Back at the shop I removed the timer (FM 0c Hubin) and put a programmable timer on a FM9 hubin timer. Tomorrow I'll try that combo. This timer and E.S.C. should give me a steady rpm throughout the flight. P.S. I flew the new set up this morning. I had to increase the rpm to 10500 to get a 5.3 sec. per lap time. I used 3 batteries to arrive at that time and one full pattern flight. It gave a nice steady rpm throughout the flights. Success at last.