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Chapter 5
Adjustments
This chapter describes how to adjust the servo offset and the seek speed circuits. These
adjustments should always be performed when a new sealed head/disk module or a new
logic and servo PCB has been installed. Adjustments can also be performed as part of a
preventive maintenance routine.
5.1 REQUIRED TOOLS
Use the following tools to perform the adjustments described in this chapter.
• small straight-tip screwdriver
• oscilloscope
• strapping wire
• voltmeter
A diagnostic panel is recommended.
5.2 SERVO OFFSET ADJUSTMENT
Adjust the servo offset circuit whenever a new sealed head/disk module or a new G9QST
logic and servo PCB has been installed. Follow these steps to adjust the servo offset
circuit.
1. Place the D2246 in the vertical position (see Section 2.5).
2. Insure that segment 7 of the installation switch assembly is set to 1 (see Section
2.5).
3. Turn on power to the drive and wait until the Ready (RDY) light emitting diode
(LED) lights.
4. Connect TP9 to ground (see Figure 5-1).
5. Trigger the oscilloscope at TPI-5.
6. Perform a repeat seek operation between cylinder 000 and cylinder 691, using
either the diagnostic panel (see Appendix C) or the procedure described in
Section 3.6.1.
7. Observe the waveform at TP7.
8. Adjust potentiometer RV4 (see Figure 5-1) to achieve the signal levels shown in
Figure 5-2.
5-1
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