HP 8112A, Operating, Programming And Servicing Manual

Page: 237 / 406

Transition Mode and
Output Control Signals
Shaper IC
Amplitude-vernier
Control-voltage
Shaper IC Reference
Current
Shaper IC
Current-mirror
Pre-Attenuator and
Output Attenuator
Control Signals
Check the logic levels on shaper IC pins for each type of transition
and output mode, against Table 10.4-3:
Table 10.4-3. Waveform Control truth table
Transition WFl
WF2 N / C
Type Pin 22 Pin 23 Pin 19
Fixed H L x
Linear
L L x
Gauss H L x
Output
Mode
Norml x x L
COMPL x x H
Check the amplitude-vernier control-voltage with the HP 8 1 12A
HI1 and 101 settings as indicated in Table 10.4-4. The voltage is
measured at the board connector side of R422.
Table 1 0.4-4. Amplitude-vernier Control-voltages
HP 8112A Setting Control voltage
HIL LOL at R422 ( typ)
+0.5
v
-0.5
v
+5.03
v
+2.5
v
-2.5
v
+2.8
v
+4.99
v
-4.99
v
< lO mV
Shaper IC reference current (Iref) can be checked by measuring the
voltage across R41 1 . The reading should be approximately 5.4 V
which equates to Iref of 2.5 mA.
Check that the signal levels at the emitters of Q400A and Q400B are
identical, as these transistors are a matched pair.
Check the relay control signals KO -K4 against Table 10.4-5:
Table 1 0.4-5. Attenuator Control truth table
Amplitude range
KO Kl K2 K3 K4
10.0
V
-
16.0
V
H H H L L
1 .00
V
-
9.99
V
L H L H L
100 m
V
-
999
m V
L L H H L
Output Disabled H L H H H
Servicing the Shaper and Output Amplifier 10.4-13