I have a US 1220 job that keeps blowing U41 on the A2 card. This is a transceiver chip that controls four multiplexed signals to the car top. The entire set of car top boards have been swapped with another car. The A1 and A2 boards have been swapped on the controller with another car. The 5 volt power supply reads perfect with not a hint of ripple. The +- 12 volt signals look great as well. It is strange to me to keep blowing the same chip on the A2 Mpu card given that this is pretty deep into the signal chain. Any US pros out there. I am dreading the possible backplane switch.
