Apple ProFile General Maintenance

Inside the ProFile (Apple owner's manual, 1983)

Handling, opening and Apple's mechanical checks for the Apple ProFile, from Apple's 1983 owner's manual and the Level II service manual. The head disk assembly (HDA) is sealed and was never meant to be opened in the field; Apple's procedures stop at the speed, index, brake and track 0 adjustments on its outside.

Handling

Apple calls the HDA "a very expensive and fragile device". The owner's manual warns that dropping or sharply jarring the drive, or letting something heavy fall on it, can damage it.

• To move the drive even a short distance, strap on the foam end caps and carry it in its small carrying container; ship it only in the original carton and packing.
• Switch off the computer first, never switch the ProFile off while the Ready light is flashing, and wait until the light has been steady for at least 4 seconds before switching off, so that the heads are parked outside the data area.
• Keep the vents on the bottom of the cabinet clear. Do not enclose the drive or stand it on thick carpet.

Safety

The power supply runs from the mains and is set for 115 or 230 V by a jumper on its board. Unplug the drive before taking the cover off. The Astec supply component lists include four 47 µF 250 V electrolytics (C6-C9); treat them as charged until you have measured them.

Opening the cabinet

From the Level II service manual:

1. Switch the ProFile off and disconnect the power cord and the interface cable.
2. Turn the drive over onto a protective pad and remove the three Phillips screws under the front panel.
3. Turn it right way up and loosen, but do not remove, the four screws on the back.
4. Pull out the lip at the bottom of the cover to free it from the frame, and lift the cover carefully, without pulling on the LED cable, resting it on the far side of the case.
5. Unplug the LED cable from the controller board.

To refit, connect the LED cable so that it leaves the board downwards and away from it, slide the four slots at the back of the cover between the inner and outer rear plates over the loosened screws, pull the cover gently forward and down, check the LED cable is not trapped, tighten the rear screws and refit the three front screws.

Power supply

With the cover off, disconnect the LED cable and remove the controller board, unplug the small white plug between the power supply and the HDA, turn the drive over and remove the four screws holding the supply to the bottom of the case. Then, with the drive right way up, remove the longer outer rear plate (two screws) and the four screws holding the supply to the inner rear plate, and lift it out. When refitting, the two cables face the HDA and the two-pronged power cable reconnects behind the orange Mylar cable.

Checks and adjustments

Apple's Level II procedures include four checks on the HDA: spindle speed, index sensor, brake and track 0.

Spindle speed

You need a frequency counter.

1. Remove the cover. Connect the counter's ground lead to a ground point on the analog board and its signal lead to TP1 on the controller board, set to read period.
2. Switch on and allow 30 seconds for the motor to reach speed. The period should be within 1% of 16.667 ms, that is 16.500 to 16.832 ms (3,600 rpm).
3. If it is out of range, remove the HDA assembly, reconnect the HDA ribbon cable to P2 on the controller board and the power connector P4 from the supply, and adjust the trimmer potentiometer on the analog board near the ground strap by P4, letting the speed settle after each turn.
4. Lock the trimmer with anti-sabotage sealant (Apple's example is Glyptol) and refit the HDA and cover.

Brake

This applies only to the older motor control board, which stops the spindle with a solenoid brake; the newer board stops it by reverse-biasing the motor. With the HDA out and the analog board removed, a 0.010-inch feeler gauge should fit snugly but slide easily between the solenoid body and the plunger plate. To adjust, Apple's procedure coats the mounting screw threads with thread locker, runs the screw in until snug, backs it off a quarter turn and sets the gap with the gauge, using a 5/64-inch hex driver.

Firmware upgrade

Early controller boards carry the Z8's program in a ROM piggybacked on top of the Z8. Apple found that heat expansion made the piggyback ROM's leads lose contact intermittently, which could make the drive write while seeking and destroy sector headers, so that the fault looked like a bad HDA. Apple's fix was to fit a Z8 with masked ROM; check for it before condemning the HDA.

Capacitors

The power supply electrolytics are listed, from Apple's Astec service package, on Apple ProFile Capacitor Replacement Guide.

Related pages

• Apple ProFile
• Apple ProFile Troubleshooting Guide
• Apple ProFile Capacitor Replacement Guide
• Hard Drive Maintenance and Repair