User Manual 3162A/B
Maintenance and Performance Checks 5-24
Power Supply
Checks
It is suggested that the first step in troubleshooting the Model 3162B would be
to check the power supply rails. If the various supply voltages within the
instrument are not within the required limits, troubleshooting the remaining
circuits can be very difficult.
The supply voltages are supplied to the instrument through the backplane. In
case of a "dead short" between one of the supplies and the common ground,
disconnect the entire supply section from the remaining circuitry, and then
determine whether the problem is in the power supply or in the remaining
circuits.
A few preliminary checks could help here. First remove the Model 3162B from
the VXI chassis. Turn on the VXI chassis and verify that the supply voltages
are available directly on the backplane sockets. Check the following supplies:
+24 V, -24 V, +12 V, -12 V, +5 V, -5.2 V, and –2 V. Check the ripple on these
lines using an oscilloscope.
Plug an extension card into one of the slots and plug the Model 3162B into the
extension card. Turn the chassis power on and repeat the supply voltage tests
as above. If one of the voltages is missing or not within the specified range, it
is possible that one of the supply lines is shorted inside the Model 3162B.
Remove the filter chokes L2 and L3 if there are problems on the +12 V or –12
V lines; remove L1 or L4 if there are problems on the +5 V or -5.2 V lines.
CPU and VXI ASIC
Checks
The most important section to be verified after power supply checkout is the
CPU and VXI ASIC section with its various clocks, address, data lines, and
chip select serial data communication components. Problems with the digital
part could cause erratic operation or erroneous response to word serial
commands.
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 Checks
S t e p
Test Point
Expected Result
1
CPU Clock – U37 pin 19
16 MHz TTL level clock
2
VXI Clock - U91 pin 159
16 MHz TTL level clock
3
ALE – U15 pin 11
Positive going pulses; period 375 ns,
pulse width 120 ns
4
PSEN – U16 pin 19
2.67 MHz TTL level pulses
5
Load a 16000-point wave and perform the
following tests during load time
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