We have a VMC & in that 24VDC power supply was dropping down (LED on SMPS was getting OFF)
There are two Operator panel IO PCBs ( A20B-2002-0520 AND A20B-2002-0521)
Pin number A1 is M (ie Minus of Power Supply), B1 is 2L+ (Ie positive polarity of power supply), A24,A25, B24,B25 are 1L+
In A20B-2002-0521, resistance between A1,B1 is 246 ohms, A1- A25 is 0 ohms and A1-B25 = 0 ohms, due to 0 ohms, we are suspecting, this IO PCB got short and need replacement with new one
A20B-2002-0520, resistance between A1,B1 is 2465 ohms, A1- A25 is infinity ohms and A1-B3 = infinity ohms