!pr2
About Disk Drive Pressure Pads.............Bob Sander-Cederlof

After you have used your disk drive for six months or so, it will probably develop a scary noise or two.  I know mine have.

My oldest drive is serial 1901 (the Shugart mechanics inside the box have a number somewhere in the low 400's).  Every once and a while it will make the most dangerous sounding noise you ever heard, something like dragging rusty chains across the road.  I have read in various magazines and newsletters that these noises are almost always caused by a dirty pressure pad.

The pressure pad rides on the top surface of the disk, pressing the disk surface down against the recording head.  It is a 1/8 inch circle of felt glued to a slightly larger plastic stud.  The shaft of the stud is split and tapered, so it will fit through a hole and lock in place.  You can easily remove the pad and stud by pressing on the split end.

But where do you get new ones?  Maybe at a computer store, but they sure don't keep them on display.  I decided to try a little home maintenance, and it worked.  I gently scraped the felt surface with the blade of my pocket knife, and all the old caked oxide turned to powder and fell off.  Then I rubbed the oxide on a piece of paper, to smooth out the felt.  After putting the drive all back together, it ran quietly.

It worked so well, I performed the operation on two more drives.  And surprisingly, one drive which had been giving lots of errors was working accurately again.

A few other disk maintenance tips:

!lm+5
One particularly noisy drive a few years ago had loose screws trying to hold the drive motor down.  A few wrist twists and all was well.

If a drive can read, but writes garbage, it is probably the 74LS125 on the analog board inside the drive.  Replace that chip for 25 cents or so, and you have saved $60 in repair bills.

!lm-5
