Figure .í. Schematic of the output power rectifier

Figiirt 4 Trouhf eshoattnii guidt - for vrtur s witc hing po h r r suppi v

presence of an AC component. For most troubleshooting, at this point it is enough to know if DC is present or completely absent, so your meter will do the job. When you find a DC voltage across the damper, and there is no DC output, the chart in Figure 4 suggests ihree parts thai could be defective;

If the damper voltage is missing, a check for the presence of ail) signal at ihe secondary of the power sw itching transformer w in order, As before, at the MOSFET gates, any signal at the secondary will be considered acceptable. The chart indicates three pans to check when there is a signal. And, if the signal is missing, the four possible causes of failure are shown.

"When no output voltage, begin troubleshooting at the gates of the MOSFETs."

The right side of the troubleshooting guide suggests a procedure when there is no signal at ihe MOSFET gates. It is not necessary to test anything in ihe power switch or output rectifier systems. Tests are confined to the input recti tier and the lCf beginning w ith a check of the input line fuse This is followed by a test for DC input voltage to the chip-

Often, troubleshooting a switching type power supply is easy because the high power available leads to charring or total destruction of the components involved in the failure, and it may not be necessary to make mam tests. However, e\en when the failure is not obvious, you can usual I> trace it quickly with a scope and a DC meter, El

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