Simracing Wheel thrustmaster tx ferrari 458 italia (t300) totaly dead

[dbach1958]

Hello Forum, it's my first post here.
I bought a used Thrustmaster TX Steering wheel as non working.
It's completely dead, not even the power indicator lights up.
Many times the issue is with the optocoppler (FOD4216) activated by 5 (3.3V) from USB, which triggers a triac to open the circuit to the PCB.
I bridged it, and this part of the power supply seems to work.
What I have read so far the normal DC voltage are 25V.
What surprises me is the fact,  that my PS output reads 32V DC and more surprising as a negative voltage (no I haven't swapped the cable :-) ).
Also I have realised, even disconnecting the power cable, the voltage stays quite a while, slowly falling.
Unfortunately I haven't any external 25V power supply at my disposition.
Any advice is very welcomed.