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PIN
NO.
1
2
3
4
5
6
7
8
9
10
11
Troubleshooting and Diagnostics
7936 and 7937
Table 8-3. Servo System Test Connector AU3, Mnemonics
(l
of 4)
MNEMONIC
SSRVPT
DEMOD-L
TEST1
ACUR
TER1-L
EXT
INPUT
lOB
SEEK CC
DLVL
ERRSIG
TF INPUT
SIGNAL
Sampled
Servo,
Positive,
Test
Sampled
Servo
Demodulation
Pulse
Test I
Actuator
Current
Timing
Error 1
External
Input
Integrated
Dibits
Seek
Current
Control
Dedicated
Level
Error Signal
Transfer
Function
Input
DESCRIPTION
Amplified sampled servo code A and B
dibits.
A versus B pulse clock (W rite clock
divided by 24).
High input disables transistor enable; low
input
enables
transistor
enable.
CAUTION: Can damage actuator/servo
PCA-Al if other faults exist.
Voltage
indication
of
current
flow
through the actuator. Scale is 0.5A/volt.
Overall timing error caused by SOS-L gap
not occurring at a designated time.
Used to increase/decrease level to triangle
wave comparator.
CAUTION: If this
level is too high/low, it can pin the ac-
tuator to a crash stop and cause HDA
damage.
Dibits which are integrated.
Test point for examining output of nega-
tive and positive acceleration pulses, in-
tegrated. Does not include external input
or internal feedback.
Sum of dedicated servo code A
&
B
dibits. Used for dedicated AGC.
Test point for looking at level into
amplifier drive triangle wave comparator.
CAUTION: Not an input - can cause
fuse/FET damage on servo PCA-AI.
Test point where an external noise source
can be connected in order to measure
the transfer function of the servo system.
8-41
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