When I wrote 'filter types' above I meant the filter envelope type sliders (IL, AL, A, D, R) should be fully down.
Also note that bobbins CP2 and CP7 on the M cards are the same thing (they are connected through the wire harness) likewise CP3 and CP8 are connected and carry the same signal.
You have to read either CP2 or CP7 when setting up the HPF. The manual says CP3, that is incorrect for the HPF, but is correct for the LPF.?
If you're trying to read levels at CP3 for the HPF, you're never get the right reading, it's a typo error in the manual.