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Troubleshooting
Component-level Troubleshooting
5
5-49
1 V
10 ms
F5-7.EPS
Figure 5-7. Waveform at Pin 6 of K2
10 k
HR2
SHUNT
1.2
R14
2V ac
±10% K5C, K5D,
K10, K13
SCOM
Ω
Ω
F5-8.EPS
Figure 5-8. Verifying the 220 µA Range of the 220 µA/2.2 mA Amp Circuit
5. Check the 2.2 mA Range of the 220 µA/2.2 mA AMP. Set the Calibrator to 2 mA,
standby. Set the external ac reference to 6.4V at 1 kHz. Measure the ac voltage at the
collector of Q4 with a DMM and verify it is 2.0V ac ±10%. If a failure is detected,
first verify the 1 kΩ shunt on HR2 is correct and it's connected to SCOM through
relays in K7A, K5D, K10, K13 and 1.2Ω load resistor R14 as shown in Figure 5-9. If
the shunt and output switching is correct check Q4, Q5, K3 and their associated
components in the 220 µA /2.2 mA AMP circuit.
6. Check the 22 mA Range of the 22 mA/220 mA AMP. Set the Calibrator to 20 mA,
standby. Set the external ac reference to 6.3V (±0.1V) at 1 kHz. Using a DMM
measure the ac voltage at the collector of Q6 and verify it is 2.0V ac ±10%. If a
failure is detected, first verify the 100Ω shunt on HR2 is correct and is connected to
SCOM through relays in K8C, K7A, K5D, K10, K13, and 1.2Ω load resistor R14, as
shown in Figure 5-10. If the shunt and output switching are correct, check Q6-Q13,
K4, and the associated components in the 22 mA/220 mA AMP circuit.