stepper-conn.jpg

Here's a picture where you can see the basics of the operation of the wheel.
Depending on the inputs A and B, the exits of P2 are 0 volt or 9 Volt dc.

Maybe one channel is working and gives a lower reading because of the high-speed pulsing,
and the channel other is stuck to 0 and 9 volts.

In that case, one of the data inputs could have bad connection.

With some reservation because I have no Scared Stiff or stepperPCB to verify.

D10 and D9 are in serie and should measure about the same.
Resistor 100K reading 60K, is that R13 ? That one is for Opto-receiver and not motor-control. does opto work?

During the spider motor test, PDB J110-4 and J110-5 are pulsing at high speed from high to low.
This signal is connected to steppermotorcontrolboard J1-4 and J1-5.
High = 12Volt Low = 0Volt. If there's no pulse, possible U3 of PowerDriverBoard is bad

If there is a pulse signal, you could perform this test to find out if the stepperPCB is working:
-machine on
-disconnect PDB J110
-jumper J1-7 (GND) to J1-4 (input A). Does the motor move 1 step ? and/or
-jumper J1-7 (GND) to J1-5 (input B). Does the motor move 1 step ?

You mention you hear the motor humming so I assume settings A.2 30 is set to "NO"

Help is on the way, but it's almost sleeping time over here but will first finish my drink.
What's the problem with the spider ?

Ok, will look there