UNITED C5 Series, Инструкция по установке и обслуживанию

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Troubleshooting
15
Troubleshooting the Circuit Board’s Low Voltage Circuit
If the control is non-operational, or the topside display is completely blank,
but the incoming voltage, transformer, and glass fuse all test okay, the
circuit board’s IC Regulator Chip should be tested.
Checking the IC Regulator Chip
Be sure your voltmeter/multi-meter is set to DC Volts to test this component.
Place one probe of your voltmeter/multi-meter on the IC Regulator Chip’s
(Testing Point 12) mounting nut, and the other on the RIGHT most pin
coming out of the top of the chip. You should get a voltage reading of
approximately 15VDC. If not, the board’s bridge recti
fi er (marked BR1 on
the board) has failed and needs to be replaced.
Next, leaving one probe on the mounting nut, move the other probe to the
LEFT most pin coming out of the top of the chip. You should get a voltage
reading of approximately 5VDC. If not, the IC Regulator Chip itself has
failed and needs to be replaced.
Troubleshooting the Light Circuit
With the light turned on at the topside, place one probe of your voltmeter/
multi-meter on Testing Point 18 (Light-B) and the other on Testing Point
19 (Light-W). You should get a reading of 12VAC if the light jumpers are
set to Low Voltage, otherwise you should read high voltage. If you read
no voltage, and the incoming power and transformer tested okay, then the
light relay has failed. If you read voltage, but the light does not function,
then the light bulb itself has failed and needs replacing.