HP 8970B - Driver Assembly Modifications

4-4 HP 8970B Option 020 Service Manual Supplement
Board Differences
Driver Assembly (08970-60089)
Driver Assembly (08970-60089)
The 08970-60089 assembly has been created from the 08970-60034 assembly with the
following changes:
1. R25, 26, 27, R39, R40 and R41 change from 214.2 Ω (0699-1911) to 121 Ω (0699-
3460)
2. Q2 is deleted and a wire is place between U33 pin 14 and the base of Q3.
Figure 4-2: Schematic differences in 08970-60089
1
1.Differences are highlighted with a shaded background.
R25
121 Ω
C28
1 uF
Q3
U33D
+
-
12
13
14
3
3
L
C55
1000 pF
VR2
13V
R24
3060 Ω
3
R26
121 Ω
3
R27
121 Ω
3
R39
121 Ω
3
R40
121 Ω
3
R41
3
19
8
1ST LO
DRIVE
1ST LO
GND
R57
100 Ω
C58
6.8 uF
5
V (F1)
-5 VOLT
REGULATOR
3
+
(SEE NOTE 9)
G
D
S
121 Ω