HP 8112A, Operating, Programming And Servicing Manual

Page: 235 / 406

Troubleshooting
Note
Shaper IC Inputs
•
If an error code is being displayed by the HP 8 1 12A you must press
a key, for example, to return the microprocessor to normal
operation before troubleshooting.
•
The component layout and locator for the main board Al is at the
end of this chapter.
1 . Set up the HP 8 1 12A as follows:
RCL
Output 0
Enabled
2. Press the key
3. Use an oscilloscope to check the signals at pins 19 and 18 of U401
against Figure
10.4-6.
Note that the signals on pins
18
and
19
are
not necessarily symmetrical.
+0 . 26 V
I
I
I
P I N 1 g I
I
I
I
I
I
+0 . 1 4 V I
I
1 00u
s
----.i
+0 . 2 6 V
I
I
I
I
I
I
I
P I N 1 8
I
I
I
+0 . 1 4 V
Figure 1 0.4-6. Shaper IC Input Signals on Pins 1 8/19
-0
-0 . 4 V
lms ------�
Figure 1 0.4-7. Shaper IC Output on Pin 1 2
4. Change the H P 8 1 12A transition mode t o FIXED.
5. Check the output on U401 pin 6 against Figure 10.4-8
Servicing the Shaper and Output Amplifier 1 0.4-1 1