HP 7925D Service Manual page 127

Troubleshooting 7925
Table 4-4. Motherboard PCA-A7 Signal Distribution List (Continued)
COMMENTS
From UNIT SELECT switch - S3. Also,
to Unit Select Display via Indicator PCA
pin A11J1-16.
To Fault Indicator PCA pin A12J1-5.
To Fault Indicator PCA pin A12J1-4.
From UNIT SELECT switch - S3. Also,
to Unit Select Display via Indicator PCA
pin A11J1-15.
To Power and Motor Regulator PCA pin
A9J 1-26. Source from + SV supply.
From UNIT SELECT switch - S3. Also,
to Unit Select Display via Indicator PCA
pin A11J1-17.
J3
A7
J2
MOTHERBOARD PCA
J1
18
4
E
R
o
XA6P1
A6
R/W
PREAMPLIFIER PCA
XA5P2
A5
TRACK
FOLLOWER PCA
XA5P1 J2 J1
K
A4
XA4P2
DRIVE CONTROLPCA
XA4P1
XA3P2
A3
SERVO PCA
XA3P1 J1
A2
A
I/O SECTOR PCA
XA2P1
K
XA1P2
A1
HEAD
ALIGNMENT PCA
XA1P1
DEFINITION
Unselected Read Gate
Unit Select Bit 1
Unit Select Bit
a
SIGNAL
MNEMONIC
US2 Unit Select Bit 2
17
UWG Unselected Write Gate
9 9
WAFL "Not" Write with No AC Fault LED
WDT
Write Data
GOT
Ground Data
WEN Write Enable
H
WENT Write Enable Toggle
WRFL "Not" Write with Access Not Ready
Fault LED
+SVRS + SV Remote Sense
US1
URG
usa
DENOTES SIGNAL SOURCE DENOTES BIDIRECTIONAL SIGNAL
4-60