Why does the fuse on the atx 2.01 power supply burn out?

Question

Electronics

The fuse on the power supply is lit. Plug it in and it burns out instantly.
And all this happens without a load on the bp. I checked conduits, transacs, diodes ... everything is working.
Please tell me what is the problem. I've been scratching my head for two months now and can't find anything on the internet.

Answer 1

A typical operand mode in such a situation is to remove the burnt fuse and instead solder a 100-watt incandescent bulb, it will light up with full heat when the PSU is turned on. Next, take a voltmeter and measure the voltage across all elements of the PSU's serial input circuit. If you find 0 volts on the filter capacitor - it is closed, on the rectifier bridge - the diodes are closed, etc.
The most common causes are bridge diodes and half-bridge inverter transistors. But the rest is not out of the question.
If the lamp does not burn with full heat, it’s more difficult here, you need to look for what the rest of the 220 volt network falls on, and why this particular part. By the way, in a working computer PSU running without load, the lamp in place of the fuse should flash brightly for a moment (from the charging current of the filter capacitors) and go into a very weak glow, sometimes almost imperceptible - the weaker it is, the higher the efficiency of such a PSU.

Answer 2

Maybe you have it with the 110/220V switch set to the wrong position?
Too little background information.