What are the categories of bad switching power supplies:
1. The fuse is blown and the machine crashes and is silent
2. Silent and chi/click when the fuse is good
3. The voltage output is ok, but the game action on this power supply is extremely difficult.
The operation of the switching power supply is as follows:
High-voltage side: brute force rectification of the mains voltage through a set of two tubes, which can be separate two tubes or lead bridge rectifiers. This is filtered through a capacitor and then goes to the switching circuit (after being reduced by other components) and the main switching transistor. The problem here is related to problem 1 and is easy to fix.
Regulation: The circuit starts the power output correctly. It runs the oscillation of the main switching transistor and reduces the output of the transformer at high frequency through a feedback mechanism. The problem here is related to 2 - a hard problem to solve.
Low-Voltage Side: This is the rectifier diode, filter choke, and capacitors that convert the high-frequency AC output produced by the transformer into the DC output required for the game. There is a small part of the circuit here that provides feedback to the regulation circuit to keep the operation stable. The problem here is related to 3.
Troubleshooting is done with the power off. Keep in mind that the issues listed as #2, #3 have to do with good fuses and high voltage parts of the board that may be live on the large filter capacitors. Some power supplies have bleed resistors across them. Just ask an electrician who knows how to repair switching power supplies to repair it, and do not operate it yourself.