Yes, the picture on the left side is the standard board inside the pendant. The two screw terminals with the wires coming from the cable should be the 24V inputs.
When you check out the diagram for the MAX831 IC you will note the following information which will help you trouble shoot the pendant.
Voltage Input to the regulator (24V) should be seen on pins 1,2,3,4
Voltage Ouput should be (5VDC) found on pins 13,14,15,16
Ground is on pins 5,7,10,12
MAX831
http://pdf1.alldatasheet.com/datasheet-pdf/view/73816/MAXIM/MAX831CWE.htmlI would first check the voltage across the two screw terminals in the pendant and make sure you see the 24VDC.
The check the voltage on the regulator to determine if it is working correctly. If you see 5V coming out of the regulator you have a bigger problem.
I will see if there is a compatible chip that can be used as a replacement.
Russ