MPG not working with mesa 7i77

Hello,

I recently wired up a MPG (PoPendant) to a mesa 7i77 and for some reason it's not working. When I hook up an external 5V power supply to the MPG and I measure between ground and A, A/, B or B/ I get a changing 0V to 3.8V signal when turning the wheel slowly. However once I wire the ground and the +5V to the Mesa card the voltage drops to 4.5V and I get no signal at all when turning the handwheel. The strange thing is that when I lower the external 5V power supply to 4.5V it does work. (I still don't get a signal on the hallscope though.)

It doesn't seem to matter if I change the encoder connectors. The 5V power supply to the mesa card is external from a PC power supply (wich isn't used for anything else).

Does someone know what could cause this? I cant find anything else myself.

Thanks in advance

How do you have the MPG connected to the 7I77? (which TB and pins)

I probably found the problem. I was checking everything the entire time on my own wiring diagram. I didn't notice I made a mistake in the diagram itself.

This is probably solved. Too bad I lost 3 days trying to figure out the problem as well as cutting and resoldering some connections.

I should mention that you might be better off with the 7I77s built-in MPG inputs
(inputs 16,17,18,19 of the field I/O) These have the advantage that
they support a 1X mode, so a 100 PPT MPG outputs 100 pulses per turn
instead of 400.

I'm out of inputs on the 7I77 so that's not an option.
The MPG does seem to give 100 pulses per turn. When the speed is set to x1 i get 1µm movement per "click" (indent) on the handwheel, x10 and x100 work correctly as well.