Apple Disk II Technical Procedures

F. COMPARATOR OFFSET ADJUSTMENT:The comparator offset adjustment should be done if the Analog board isreplaced.It ensures that a "one" stored on the disk will be read as a one, and a"zero" as a zero.Materials needed:1. Apple ][ system with known-good disk drive and interface.2. Disk Calibration Diskette (P/N 686-0006)orDisk Alignment Aid diskette (P/N 652-0199)3. Scratch (expendable) diskette4. Drive to be tested5. Oscilloscope6. #2 Philips screwdriverTo run the Amplitude Test:Apple and Drive Set-up:1. Turn the Apple ][ f s power off.2. Install the known good Disk Interface card in slot 6.3. Connect the known good drive to the Drive 1 position of theInterface card.4. Remove the cover from the drive to be tested. Connect the drive tothe Drive 2 position on the Interface card.Oscilloscope Set-up:5. Set the oscilloscope controls as follows:SECONDS(or TIME)/DIV = .5 uSEC/DIVV0LTS(or AMPLITUDE)/DIV = 1 V/DIV (.1 V/DIV for 10X probe)Trigger source (INT/EXT) - INTTrigger slope (POS/NEG) = NEGInput (AC/DC/GND) = ACDisplay (CH1/CH2 or A/B) = CHI or ASweep Mode (AUTO/NORM) - AUTOPower (ON/OFF) - ONINTENSITY and FOCUS for a clear sweep display6. Connect the probe cable to the channel 1 (or A) input of theoscilloscope.CONTINUED ON NEXT PAGEDisk Drive Calibration rev. 09/10/82 page 3.20