b. If the output does not toggle, set the Counter to READ LEVELS-Trigger Level mode and check the
input pins of the comparator with
an
oscilloscope. The voltage at U36B pin 5 should vary between
_+
2.5 volts as the Trigger Level Control is adjusted. At pin
6,
the DAC voltage should be slewing
rapidly across its range in a search routine. If both of these inputs are correct, replace
U36.
8-357. To check the Sensitivity Control Switch, U28C leave the counter in the READ LEVELS mode, and
press the SENS key ON.
a.
As
the Trigger Level Control is rotated, the output of U28C pin
4
should vary from
+
40
to
-40
mil-
livolts.
b. With the SENS key
OFF,
the output of the switch should remain at
+
40
mV, regardless of the Trig-
ger Level Control setting.
c. If the switch does not function correctly, check the TI'L levels from U29 pin 27 to the control pin 9
of
U28C. With the SENS key ON, the level should be a 'ITL HIGH; with the SENS key OFF, the
level should be a
TI'L LOW.
8-358.
MEASUREMENT BLOCK TROUBLESHOOTING
3-359. Use the Failure Messages from
Table
3-4,
in the Operating and Programming Manual, to help
troubleshoot the Measurement Block. The failure codes which indicate problems in the Measurement Block
focus primarily on the Measurement microcomputer (MCU) or on communication problems between the MCUs.
3-360. The failure codes 7.0 to 7.5 deal primarily with failures of the Measurement MCU. During power-up, the
MCU performs a RAM and ROM check. If it passes the test, the processor alternately flashes the front panel
GATE and ARM annunciator lights during the power-up sequence. It then carries out an
110 port check, and
also checks the MRC. The processor will also detect the absence of the 10 MHz Time Base signal. All the failure
codes in this group are generated solely by the Measurement MCU.
3-361.
The 9.X failure codes focus on data communication between MCUs. If the Measurement MCU does not
respond correctly, the Executive MCU
will generate one of two possible failure codes (9.1 or 9.3).
3-362.
If no failure codes are generated and the operation of the Measurement MCU is in question,
it
is pos-
sible to test the MCU separately from the rest of the instrument. This is done by placing the
MCU
into a diag-
nostic mode using the following instructions.
Setup
a. Begin with the 5334B in STANDBY.
b. Connect a jumper between the Measurement
MCU (U29) TY12
and
Ground
(TY8).
c. Apply power to the 5334B and observe that the Counter displays "FAIL 9.1".
d.
Remove jumper from TP12 and TP8.
HP
5334B
-
Service Manual
8-51
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