HP 5334B Service Manual page 172

Be careful to place the scope probe on one pin at a time. If two pins are
accidently shorted by the scope probe, you may not observe the correct
signals. You will have to repeat the steps a through d of the Setup proce-
dure.
Test
a. Use an oscilloscope to observe the signals described below. All are 'ITL levels
U29 Measurement MCU
Pin 1
-
4 MHz sawtooth waveform
Pin 2
-
4 MHz sine wave with no dc offset voltage
Pin 3
-
LOW
Pin 4 and Pin 5
-
Line Toggles
Pin 6
-
HIGH
Pin 7 to Pin 15
-
Line Toggles
Pin 16
-
HIGH
Pin 17 and Pin 18
-
Line Toggles
Pin 19
-
HIGH
Pin 20
-
LOW
Pin 21
-
LOW
Pin 22 to Pin
37 -
Line Toggles
Pin 38
-
HIGH
Pin 39
-
HIGH
Pin 40
-
HIGH
b. If any signals measured are incorrect, replace the Measurement MCU (U29).
8-363. If there is still trouble in the Measurement Block, check to see if a RATIO A/B measurement can be
performed by connecting the 10 MHz Time Base output from the rear panel to the Channel A Input and setting
the COMMON A mode. This ratio measurement uses only the E and T registers in the Multiple-Register
Counter (MRC) and not the Interpolators. The measurement should be 1.000 000
&
.000 001.
8-364. If the Counter does not perform the RATIO measurement correctly:
a. Verify that the 10 MHz Time Base signal is getting to the MRC at U20 pin 21. This signal should
have a minimum amplitude of 600 millivolts peak-to-peak.
b. Check the Channel A and B inputs to the MRC U20 at pins 28 and 30. There should be a 10 MHz
signal with an amplitude of 800 millivolts on a dc level of
+
2.4 to
+
3 volts at both pins. Also check
to see that the control lines from the Measurement MCU at pins 1,3, and 40 of U20 are changing
state at 'ITL levels.
c. If all of these signals are observed, yet a RATIO A/B measurement cannot be performed, replace
MRC U20.
HP 5334B
-
Service
Manual
8-52