Hello, filter well or monochromator which rotate to change the wavelength inicialization by optocuppler. You need to go inside and chech fist the optocuppler which responsible for counting rotation. Second reason can be photodiode which responsible for detecting filter position.

Hello,

Thank you @Karen A. Darbinyan.

Is it possible, if it's the case, to change the photodiode ?

And do know where the optocoupler is located ?

Does the photodiode need to be soldered to the detector board?

Depends from PCB. Any wheel or rotation should has counter or position indicator. Filter Wheel initialization fail means system can not find location or relocate the filter wheel. The most common reason is optocoupler problems.

The position indicator or optocouplers can looks like in attached pictures.

OK, thanks for your help

I hope it will work

If I get any problems, can I turn back to you ?

Mine looks like this :