WSM6 Manual
Document Ref: UM-8270-000
Issue: A Rev 0
Section 8
91
8.4 Diagnostic Procedures
To carry out full diagnostic checks, the upper board may have to be removed to access all the test
points. Three flying leads are needed to connect the two boards together – PL2 to SKT2, PL3 to
SKT3 and PL4 to SKT4.
CAUTION
To avoid damage to the circuitry during testing, make sure the ON/OFF switch on the
end-cap is set to OFF and only set to ON for the duration of the test.
8.4.1 Quiescent Checks
8.4.1.1 Quiescent Current
1. Switch ON the WSM6 by rotating the ON/OFF switch.
2. Check the quiescent current on the multimeter. This should not be less than 1.5mA. It may be
necessary to wait a minute or two if the circuit has not been switched on for some time, and
the electrolytic capacitors need time to re-form. A steady-state current higher than this
confirms a fault condition exists. Occasional excursions above this value are normal.
3. If the current is higher, a fault has occurred in the electronics.
8.4.1.2 18V Supply Voltage
1. Set the multimeter as a voltmeter on a 25V dc range.
2. Connect the multimeter to monitor the voltage on the positive tag of the large capacitor (C16)
on the lower printed circuit board (PCB) – positive terminal to C16, negative to C16 –ve.
3. The voltage should be approximately 17.4V. If it is zero the lower board is faulty.
4. If the C16 voltage is less than 17V, but not zero, the lower board is faulty.
8.4.1.3 5V Regulator Output
1. Connect the positive lead of the Multimeter to U19, pin 8 (use the hole closest to TP3 of the
lower board). This voltage should be 5V ± 0.2V dc.
2. If the voltage is outside the limits, either the 5V regulator or part of the circuit loading the 5V
regulator is faulty.
3. To determine absolute fault, remove the upper board and repeat the test. If the problem
persists the lower board is at fault. If the problem clears the upper board is faulty.
October 2011
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