Hello everybody!

I tried to replace belt on my Sony WM-F701C but could not open the cover

Removed all screws

Uplifted cover from battery adapter side, but the cover did not uplifted in the corner near the door lock (or minus contact of battery adaptor).

I am afraid to put a lot of force because of player in mint condition.

When I replaced belt for Sony wm-702 the cover opened without any issues.

May be some "secret" is for wm-701? 

You have to remove the small spring that holds the door latch on place first, use tweezers and don't lose it.  Remember what way it came out ( I like to take pictures before I take a walkman apart) , then remove the screw and push the latch ( the metal piece that the screw goes into) into the battery compartment.  Once you do that it should just open up for you.  Make sure you slowly open it toward the headphone jack breaking it free from the little claws on the side.  I have 3 of these and they all opened the same as the 702 if I remember right!

  lot of thanks to Minty and martymcfly!

I opened 701c by using bank plastic card  Nail was brocken  There is a small difference between 701c and 702 - different door lock system. In 701C there is small metall thing which holding door lock. The screw inserted in this thing in the 701C . when you remoove screw, this small thing became free and change own position/ So required more power to disassemble back cover.