Head loading modification installed and tested

CONSTRUCTION AND INSTALLATION OF THE STOP ON HEAD LOADING MECHANISM

I bought a small bracket to install on the drive. It is needed to add a small fixed pre-movement of the load mechanism at all times, which will permit the arm to be moved in and out even when the heads are not loaded down on the disk. 

The solenoid that loads the heads down on the disk surface pulls a rod that pivots a structure and removes a wedge that holds the heads up high of the surface. The spring loaded structure lowers them down and keeps a fixed downward pressure as they fly. A bent lever on the structure contacts a microswitch when it has pivoted all the way to the point where the heads are down on the disk surface.

That bent lever moves to its full rest position when the solenoid is not activated, then is pulled to the other extreme as the pivoting structure loads heads. When in full rest position, the structure has a ridge that blocks the disk arm from moving out from its retracted "home" position. 

Since my scheme blocks the solenoid from activating, thus blocking the heads from lowering on to the disk surface, I want the arm to move freely without head contact. I discovered that a vary small amount of rotation of the pivoting structure clears the block on arm movement but does not begin to lower the heads at all. 

The bracket I bought was fastened on the mechanism to hold the bent lever slightly in from its rest position, enough so that the arm can move. It fits to the rear of the bracket holding the solenoid and microswitch, bent over to fit behind the bent tab which operates the microswitch. 

Top view

Side view

TESTING THE PRELOAD TO ALLOW ARM MOVEMENT

With the bracket in place, I tested the free movement of the arm assembly to position the heads to any of the 203 cylinder positions radially towards the center of the spindle. Everything checked out well. A future test will verify that with the switch installed and set to the Virtual 2315 position, we can get the drive to go Ready without the heads down on the disc surface. 

Arm fully forward past cylinder 203 position

Arm in its retracted Home position - cylinder 0