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_ ADJUSTMENTS
The information in this chapter pertains to the HP 9153A and HP 9154A with S/N prefix of 2515A and
lower.
There are no adjustments required for any products with S/N prefix 2702A or higher or for the HP
9153B/54B.
[1] INTRODUCTION
There are no adjustments for the Winchester Disc Drive.
The adjustments explained below refer to the 3
1/2-inch flexible disc drive in the 9153A (S/N prefix 2515A and below only). There are no adjustments on
the HP 9153/54A S/N prefix 2702A and above as well as the HP 9153/54B.
The Phase Lock Loop (PLL),
Read
Pulse Width (RPW), and Write Pulse Width
(WPW)
adjustments
for the 3 1/2-inch
flexible drive
should be performed at an authorized Hewlett-Packard Repair Center and not in the field.
The following procedures and associated test points are provided to help isolate a failure to the 3 1/2-inch
flexible disc drive or Controller PCA.
[2] PREPARATION
FOR
ADJUSTMENTS
(HP 9153A S/N prefix 2515A and lower)
To gain access to the components for the adjustments, perform the following steps:
1. Remove the top cover as stated in Chapter 6, subsection [2].
2. Remove the DC power connector from the flexible disc drive.
3. Lift the flat ribbon cable from between the disc drives and disconnect it from the flexible disc
drive.
4. Remove the screw that secures the drive mounting assembly to the mainframe.
5. Set the assembly down so that it rests on the side of the Winchester disc drive with the mount-
ing plate next to the front of the chassis.
6. Reconnect the power and flat ribbon cable connector to the flexible disc drive.
All the adjustable components are accessible through cutouts in the controller mounting assembly.
[3] ADJUSTMENTS
(HP 9153A S/N 2515A and below)
PHASE-LOCK
LOOP ADJUSTMENT
The PLL, as well as the RPW and WPW
adjustments require the FDC chip to warm up prior to adjustment.
Perform the following procedures at an ambient temperature of 25° C (77° F) in the order specified.
Use Figure 7-1 for locating test points.
The PLL adjustment should be performed when the flexible disc drive exhibits read/verify errors or fails
the "VERIFY"
test (Test 7).
7-1
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