Issue with Amada VIPROS QUEEN PHMC error (2050)

Good morning/afternoon gentlemen,

I have an issue with an AMADA vipros QUEEN equipped with a YUKEN LSV.
We've had an error 2050 (PHNC error) on this machine lately. The pressure measures 0 kn when the hydraulic pump is running.

We sent the LVDT and LSV amp to be checked but the error still goes on.

Here is what I've done:
- I first thought the pressure sensor could be faulty. I sent an analog signal to simulate around 70kN of pressure. The error would not trigger, but the striker won't move, the machine ill just fly to its various cordinates without punching, as if the punching key was on "OFF". What I find odd is the absence of error since the striker is expected to move but ultimately doesn't.
- I checked cylinder FB signals: I have about 5VAC going to the cylinder sensor, 3V AC coming back to the LVDT and 3V DC going to the LSV amp.
- I measured voltage and intensity in the out port of the LSV amp: when unplugged, I have around 19V DC, but as soon as my valve is plugged in, the voltage falls back to 0. Is it normal ? During a cycle, no tension or intensity going to the servo can be measured. Impedance of the valve is around 3 ohms, and insulation between coils and ground is good.
- I ultimately tried to actuate the valve by unplugging the LSV amp and sending an analog signal to the valve. I was able to operate the valve by nearing 16-17 V (can't remember the intensity though). The machine went Estop almost instantly, so I assume the system can read the cylinder position correctly and compare it to the command ?)

I'm thinking either the LSV amp has not been repaired correctly, or the conrol loop is faulty. I couldn't find the reference voltage sent by the PHNC board to control it, does someone has this info ?
What is your take on this issue ? What would you suggest we look into ?

Thank you for your help !

Update:
Apparently, you can try to control the cylinder position by moving the switch "Loop pos" to off, and moving the potentiometer Null -1 on the LSV amp.

In theory, you should be able to actuate the valve with this and control the cylnder's movement by monitoring the voltage on the "check" pins on the LVDT. -3V DC is the top dead position, -2.7V DC should be the expected position of the cylinder under normal conditions.

In my case, moving the potentiometer while by-passing the position control loopback still results in zero movement.
What do you make of it ?

Regards.

You can turn off the pressure transducer in the machine parameters. That might tell you something.