PCC D3400 - Read Decode Circuit Adjustments; Read Pulse Narrow (RPN) Pulsewidth Adjustment

830D
6.12 READ DECODE CIRCUIT ADJUSTMENTS
Read decode test and adjustment procedures (Read /Wrlte Assembly No. 103751) are
contained in Paragraphs 6.12.1 through 6.123.
NOTE
The oscilloscope time base must be calibrated either via
exterior calibration device
or using the 10 MHz oscillator
on the Logic PCBA.
6.12.1 READ PULSE NARROW (RPN) PULSEWIDTH ADJUSTMENT
6.12.1.1 Test Configuration
(1) Remove the interface connector and Terminator PCBA from connector J101 and
J1 02 on the Logic PCBA.
(2) Connect a disk exerciser having read/write capability to J101 or J102 on the Logic
PCBA.
(3) Apply power to the exerciser and the disk drive. Observe that the READY indicator
is illuminated;
allow a 5-minute warm up period.
(4) Write
an all-zeros pattern via the disk exerciser.
(5) Connect
oscilloscope Channel 1 probe to TP25. Connect the test probe ground
clip to ground reference TP17.
(6) Set sync to internal, normal mode.
(7) Set oscilloscope to trigger on the position slope of RPN.
6.12.1.2 Test Procedure
(1) Establish test configuration described in Paragraph 6.12.1.1.
(2) Observe
RPN waveform on oscilloscope Channel 1 (TP25), shown in Figure 6-19.
(3) Measure RPN pulsewidth at the 50 percent points (on oscilloscope center line).
(4) Acceptable Limits
• 40 nanoseconds (minimum)
• 45 nanoseconds (maximum)
6.12.1
.3 Adjustment Procedure
When the acceptable
limits are exceeded, the following adjustment is performed.
(1) Establish test configuration detailed in Paragraph 6.12.1.1.
(2) Adjust R157 on the Read/Write PCBA to 42 nanoseconds.
T~25 R~N ___ ....;.;50.;.;;.%-==-0 ____ _
I
j I \--=:- 50%
T~3 -----~I.~· I~--~~------
ALL ONES
I '
i 'ONES' WINDOW I
r-----ADJUS TED---i
INTERVAL
Figure 6-19. Read Pulse Narrow I 'Ones' Window
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