Lay the unit face down.
Look at the top center from the rear of the unit.
You will see a gray metal arm (see photo).
I call it the Head Retraction Control Arm, because if you look on the
left side, you will see two white plastic assemblies.
They go up and down and push and release this arm.
If you push this arm with your finger, you will see the heads go up and
down. But mostly, I call it that
because it sounds good…lol. Anyway,
this control arm needs to come out.
Remove the metal retainer ring with a small screwdriver, being very careful that it doesn’t fly across the room.
Stand the unit upright and look down from the top.
The control arm meets another gray metal lever.
You’ll need to push down slightly on this other lever as you remove the
control arm. The control arm will
then slide straight out from the rear.