Test LinuxCNC without motors and encoders connected

I have 0.87, even when i wiggle the shaft in both ways.
And I only have one encoder dismounted from the CNC machine.
But I'm pretty sure that the encoder is still working.
I've started the CNC just before the dismounting, and it was working fine.

What does LD5-12 means ?

As far as I could understand the encoder signal mode was 9 = LD5-12 (probably line driver 5-12)

I would verify your wiring, perhaps just supplying 5V to the encoder and checking the unconnected output pins

Ok, I've done a test. I've disconnected the encoder from the 7i77
When I supply 5V to the encoder, I measure 3.7V on the output pins
When I turn the encoder, the value changes.
By 10V, I get 8.7V and by 4.7V there's 3.2V on the outputs.

Then I used the onboard 4.7V, and the output was also 3.2V.
But when the outputs are connected to the 7i77, there's 0.87V

If (with 5V power) you measure across A, /A, is the voltage +3.2V in one state and
-3.2 in the other state?

If not, the outputs are not differential

With 5V I measure 3.5 V. While turning the encoder, I'm not able to read the output. It changes constantly.
But after I turned the encoder to the left or to the right, I see -3.7 or +3.7. But it is unpredictable. I mean.. after turning left, it could be + or -.
In de description of the encoder i could read that it is a incremental encoder. But I don't know what the difference is between incremental and differential....

Peterdeleu wrote: But I don't know what the difference is between incremental and differential....

It seems likely that your encoder is both incremental _and_ differential.

An incremental encoder outputs a quadrature signal
AB
aB
ab
Ab
AB
and so on.

A differential encoder sends the signals as +ve and -ve differential voltages on two wires per phase

A+ B+
A- B+
A- B-
A+ B-

A single ended encoder sends the signal as 0V or 5V relative to ground on just one wire per phase

A5V B5V
A0V B5V
A0V B0V
A5V B0V

Depending on exactly where you stop turning the encoder you can see any of these states. So you would expect to not be able to predict the output when turning by hand.