The only one I ever saw fail, was breakdown between the windings - I thought the design and construction was supposed to make that impossible, but it happened.It is an input filter choke on the mains input. It has two windings. One for live and one for neutral. It is part of the circuit to reduce electrical noise at the switching frequency from getting into the mains supply and causing interference with other equipment. It will also attenuate electrical noise that is on the mains supply entering the supply. To check it measure the resistance of each winding. They should have a low resistance reading of less than a few ohms. Both windings should have the same resistance. You then need to use a high voltage insulation tester (Megger.) to test the insulation between the windings and between each winding and the core. You could also check that the inductance of the windings matched the manufacturers data sheet.
Les
Mine was a TV with a VGA connector that was being used on the PC. Always unplugged when not in use, it made a funny smell one time I plugged it in. Fully prepared to scrap it, I opened it in case of useful salvage - saw how easy, and fixed it.Hi Ian,
That was the mode of failure of the only one that I have seen fail. There was no plastic former for the windings and the winding insulation was breaking down to the core. The unit was blowing the input fuse so I was expecting The main switching device to have failed short circuit. It made for a nice easy fix as I found a suitable replacement in my junk box. I find the TS's fault finding method rather odd just testing components without logically locating the fault.
Les.
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