A21 Troubleshooting - HP 5340A Operating And Service Manual

5-31. There will be two types of test results: The 5340A will display all zeros or it will display
some number. For the first and fourth test in each group, the 5340A should display all zeros. The
second and third test should cause a number to be displayed, which is approximately
150 MHz. The exact value of the display is not important; it is important to note if the display is
all zeros or some number.
5-32. To simulate the RANGE setting, connect to chassis pin connections XA19B(S), XA19B(R),
tively, are positive true. Thus to simulate Range #6, do not short cut Binary 4 and Binary 2.
5-33. If any test fails, first check the action of the range binary to decimal decoder, which should
output a TTL Low for the selected range. For example, when XA19B(P) is shorted to chassis
(selecting Range #6) the 6 output (pin 7) of the IC should be 'M'L Low. All others should be
TTL High. The decoder
is
in a group fails, check the action of the lower limit comparators. This is U19 and U20 on both
05340-60018 and 05340-60067. If the fourth test fails, check the action of the upper limit com-
parators (U25 and U26 on 05340-60018 and U26 and U27 on 05340-60067). If the second or third
test fails, check both sets. These can easily be tested using a logic comparator.
5-34. Check also the output of the binary
the table. This is U12 and U21 on 05340-60018 and U6 and U7 on 05340-60067. Check also the
associated inverters.

5-35. A21 Troubleshooting

5-36. Disconnect jumper W2 on A20 and install logic clip on A21 U4. Push front panel RESET
pushbutton.
5-37. Use HP 105261' Pulser on A21U2(9) and step through the program. Check for proper
branching per Figure 5-4. If the program address will not increment, (locked in a loop) deter-
mine from Figure 5-4 which test or action is not being completed. Then check A21U12 or U13 to
verify that proper selection is taking place there. If that
of the failure.
5-38. If incorrect branching is occurring, a test is giving incorrect results or the A21 circuitry is
interpreting it incorrectly. Check the input of A21U12 for proper test logic levels, a s noted in
Figure 5-4.
X.
These pins, which have binary weights 4, 2, and 1, respec-
U27 on A20 05340-60018 and U28 on A20 05340-60067. If the first test
N counters for agreement with the value of N listed in
Maintenance and Service
OK, trace the circuit to find the cause
is
Model 5340A
N
times
i
5-19