Racal Instruments 3152, User Manual

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Maintenance and Performance Checks 5-18
Problems in the CPU and the digital circuit may cause a complete
malfunction of the entire instrument. The CPU would not start
generating control signals. This makes it impossible to
troubleshoot the remaining circuits. Check the various components
associated with the CPU circuitry, its clocks, and the components
associated with the VXI ASIC using the information given in Table
5-1.
Table 5-1 CPU and VXI Interface Checkout Procedure
Step Test Point Expected Result
1 CPU Clock - U87 pin 19 16 MHz TTL level clock
2 VXI Clock - U109 pin 159 16 MHz TTL level clock
3 ALE - U85 pin 11 Positive going pulses; period 375 ns,
pulse width 120 ns
4 PSEN - U74a and U74b 2.67 MHz TTL level pulses
5 Load a 10000-point wave and perform
the
following tests during load time
6 RD - U87 pin 16 Negative going 400 ns width pulses
7 WR - U87 pin 17 Negative going 400 ns width pulses
8 LDACK - U87 pin 5 Negative going 6.5 µs width pulses
9 ASIC LCS - U104 pin 11 Negative going 6.5 µs width pulses
10 LR/W - U93 pin 19 Negative going 60 µs width pulses
Output Amplifier and
Amplitude Control
Checkout
Problems with the output amplifier and amplitude control circuits
can be detected if the Model 3152 accepts word serial commands
and responds correctly to word serial queries, but fails to output the
correct waveform with correct amplitude and offset levels. If there
is a problem with the output amplifier or with the amplitude control
circuit, proceed with the checkout procedure given in Table 5-2.
Before starting the following procedure, reset the Model 3152 to the
factory defaults using the *RST command. Then send the
command OUTPUT ON.
Table 5-2 Output Amplifier and Amplitude Control Checkout Procedure
Step Test Point Expected Result
1 Junction of R57 and R58 750 mVp-p sinewave, 1 MHz
2 Junction of R18 and R19 10 Vp-p sinewave, 1 MHz
3 Voltage across R37, R41, R46, and R49 Approximately 1.6 V
4 CE voltage on Q9 Approximately 2.8 V
5 U7, pin 1 Approximately -1.1 V
6 U7, pin 7 Approximately 400 mV