Thanks, I tried to upload the photos from PC again, as well as from phone, but unfortunately it keeps giving error at the end of the upload, I don't know if it's a problem with my photos, even if they are Jpeg and with dimensions less than 14 Mb! However the situation is that my nms 1515/00 recorder does not have the two neighboring white gears circled in the image on the first page of this post, I think this is not correct, considering that when I press REW and FF the white support moves but no gear carries the movement required. 
Thanks guys, actually the gears were missing ..
Now the FF and Rew functions work! Unfortunately, during the assembly I have ruined the double gear .. I have already placed a new order from the seller on ebay ..