In very old robots, similar problems arise due to the contactor. Because life is 10 years. Some factories change the maintenance frame once every 3 years. You will see 3 contactors on the right side of the zone you are pictured. Measure the main phases with a multimeter. you need 260-277 volts between the two phases. First measure the input of the K1 contactor, if the voltage is correct, press the motor on button from the control and then measure the output. Verify voltages K1, K2 and K3. If the main phases are correct, measure 24V from terminals 7 and 8 of contacts K1, K2 and K3. If they are correct then verify the auxiliary contacts on the upper floors. I've uploaded the page with the contactors in addition to help you. Good Luck.
Replace K3 contactor. This is common when a weak K3 contactor does not pull down all the way. The resistors are used to limit the in-rush current to the rectifier (DC-Link) when K1 & K2 are enabled, but motors are not yet engaged. Contactor K3 pulls in to release the brakes and also bypasses the resistor to provide the necessary current to the rectifier. When the contactor does not bypass resistor, all the current flows thru the resistor and it quickly overheats. Dirt/dust and age are the enemy with these contactors.
We automatically replace all 3 contactors (and aux contacts on top) on refurbs/sales and highly recommend it when found during service.
If the resistors have been overheated, you may have to replace them too.
The DC-Link low error could be the resistors have opened or the circuit breaker tripped.
