PCC D3400 - 5.7 Temperature Compensation Pcba

5.7 TEMPERATURE COMPENSATION PCBA
The Temperature Compensation PCBA is installed in 200 tpi 03000 Disk Drives. The PCBA
is located adjacent to the Read/Write PCBA and is approximately 203.2 mm (8 inches)
long by 101.6 mm (4 inches) high. The Temperature Compensation PCBA operates in
conjunction with one externally mounted termistor to provide
thermal compensation to
200 tpi models. Refer to Schematic No. 103976 (sheet 3 only) and Assembly No. 103977.
Figure 5-8 illustrates the placement of the five molex connectors located on the
Temperature Compensation
PCBA. These connectors provide power to the PCBA in
addition to providing input and output signal paths between this PCBA and the Logic
PCBA, the Servo PCBA, and the externally mounted thermister. Refer to Schematic No.
103976 (sheet 3 only) for the following discussion.
Capacitors
C1 , C2 (zone E7), and C4, C5, ca, C7 (zone H7) are employed for power supply
decoupling.
The internal temperature sensing thermister, RT2, is mounted on the
positioner baseplate
and is connected to the input of amplifier U6 (zone C7) via pin 1 of
J505. R12 is used for linearization of the input; R13, R14, and R15 are used for scaling the
closed-loop gain of U6 as monitored at TP3.
The output of amplifier U6 (zone C7) is applied to pin 2 of amplifier U8 (zone C6). The
second input to U8 is applied to pin 3 and is provided from R16. U8 is a X1 gain difference
amplifier whose output is proportional to the difference between the output of
U6 and the
reference voltage generated from
R16.
TPI20
15 ClOSED-LOOP GAIN ADJUST
Rib AMPLIFIER GAIN
DIFFERENCE ADJUST
TP6
o
TP7
0
OTPS
mO
TPll
0
0
TP8
0
TP10
Figure 5-8. Temperature Compensation PCBA, Test Point and Connector Placement
1921
630D