What would I do if I had a blown fuse in my arcade’s monitor chassis? Well a couple of things, first being to make sure it was the correct size and type (Amps, slow blow or fast blow). Next I would likely put in a new one and turn the game back one. Watch the fuse and see if it blows right away or not. If it doesn’t then play your game!!! BUT if your fuse blows, do not keep replacing it with a new one, because it will blow also. It’s time to pull the chassis out of the arcade machine and put it on your test table. The first place I would test in this case is all of the diodes around the fuse. OK now testing a diode is super easy. A diode is like a one way door, it will let current through in one direction and block it from coming back in the other direction. So get out your Multimeter. Set it to ohms, then touch the red lead to one end of the diode and the black lead to the other. It doesn’t matter which. Check the reading, remember and then switch the red and black leads. One way will give you a reading like .850 (maybe .500 to .900) and the other will probably show no reading, because it should be blocked by the diode.. But if you get a reading and the other way is open (OL) then it is a bad diode, I would remove from the board and retest it.
A diode should read relatively low resistance in one direction and very high resistance in the other direction. There are a ton of videos on Youtube on how to properly test a diode. Please watch a few to get a better understanding.