I'm attempting to repair (with not much success) a flyback power supply circuit. The circuit takes input of 240v AC and has output rails, from a flyback transformer, for 5v and 12v DC. I have traced the input up to the primary side of the flyback transformer where it measures 342v DC. There is, however, no voltage on the secondary side of the transformer.
Questions are thus:
- I have disconnected the secondary side of the transformer from the load, in an attempt to rule out a short on the 5v or 12v rails. There was still no voltage on the secondary side. Is this logic sound or would it be expected that a flyback transformer whose secondary side is not connected would have no voltage?
- What could cause no voltage on the secondary, when a DC voltage exists on the primary? Could the flyback transformer itself be faulty?