I met the same situation whenever I tarried to repair Switch Mode Power Supply. I find it like what Nigel stated, not only one component that goes wrong.
He's also got the added complication of having put a 9A fuse in, so probably destroyed even more bits.
It's VERY, VERY rare that only a single transistor fails - it's a domino effect, one goes and bits fail everywhere.
I would imagine the FET you replaced has probably blown again instantly.
You need to locate and replace ALL faulty components, before you ever switch it on.
I have not replaced the fets that I removed. I have them but expected to see a circuit NOT blow the fuse. Now that I see that it does, even with the fets removed, I am further confused. I am combing this thing to every detail right now and just cannot get any component to test really bad with a DMM. I realize powering up can change things. There is obviously a very hard short somehow, some where. I was wondering about the transformer on here since all leads test 0 ohms to each other but Judging by wire size and windings, that is probably about right. I pulled the main cap off and tested it with a cap tester. all good. Also have a line of 5 transistors for the output stage and tested all of them for a short with nothing. I guess I am combing for low resistance or a shorted diode simply due to how it reacting with power. No worky is one thing but popping the fuse instantly sure makes me thing input AC side or right after the Bridge somewhere.
Again, can bridges diode test good, yet short out with power?
The coil is part of a power filter circuit. I am confused! Is the fuse for the AC power input blowing, or is it between the power-supply and the amplifier??? Smps (switch mode power supplies) can be cery hard to fix!I am still fighting a hard short in an audio amplifier board. Found a dead shorted mosfet which took me from a measured 0 ohm resistance on the DC buss to the mohms. Problem is I am still blowing the fuse. Just cannot figure this out.
The pic shows a coil that is being used on the AC input stage. Each side of it is in series with the bridge rect. I am at a loss to honestly know what it is and what it is doing. Does not seem to be a transformer. Each side measures 0 ohms. Just wondering it's function.
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