Vector 4 - Page 135

VECTOR GRAPHIC, INC.
L2 Check Floppy VCO Center Frequency
Using oscilloscope or frequency counter, measure frequency at pin 7 of
Ul. '
If oscilloscope or frequency counter shows clean square 500 kHz wave (2
micro-second period) with 50% duty-cycle, floppy VCO is o.k. Go to 1.3,
below,
If wave is not as deseribed, continue.
Using small standard serewdriver, adjust right-hand potentiometer R15
until oscillosecope or frequency counter shows wave pattern described
above,
If no amount of adjusting will bring wave pattern within desired range,
replace disk controller board.
If system uses floppy drives only, go to 1.4, below.
In the following step, refer to Section III 3.1, DISKTEST Commands Used In
Alignment, for a brief explanation of some of the commands available to the
DISKTEST program.
de
1 1-2
Enter the command DISKTEST [RETURN)]. When the screen prompt
appears, enter Y to continue, then select § to check hard disk. When
the screen offers the following prompt, enter the underlined response:
SELECT OPERATION (? FOR HELP): RD
Then press the [RETURN] key for each following prompt. This will cause
the disk read/write head to access the disk surface continually, allowing
the oscilloscope to obtain the necessary pattern.
Using oscilloscope or frequency counter, measure frequency at pin 10 of
Ul.
If oscilloscope or frequency counter shows 10 MHz square wave (100
nanosecond period) with 50% duty-cyele, hard disk VCO center frequency
is o.ke Go to 1.4, below.
If wave is not as deseribed, continue.
7200-0001 09-01-82