Post a picture of the boards with what is currently connected. Does the fuse blow if you disconnect the MPU?

You have a 5amp slo blo and set for 120VAC on the transformer ?

Sure would like to see a picture of the power supply with the CN1 connected

Assuming CN1 is wired right and looking at the power supply schematic, likely P2 bridge rectifier is shorted. You can remove the board and on the bottom side, measure all the adjacent pins. I believe you will find a AC~ is shorted to either the output + or -.

P2 is KBPL 8005 50v 8 amp bridge rectifier farfalla power supply (resized).png

No. Test your P2 again. I don't see the results I think I am seeing to call P2 a failure. Can you set your meter to ohms and let me know the results?

one of the ~ to + and then ~ to the -

then the other ~ to + then ~ to the -

2018-07-27 18_25_21-Zaccaria Farfalla blowing fuse F2 _ Tech_ Early solid state _ Pinside.com - Inte (resized).png

Well, that is weird. That is how bridge rectifiers normally short out. In any case, can you test the + and - together and then both ~ together?

If both AC ~ ~ terminals are shorted, then you may have a short (solder bridge) between pins on your CN1.

Can you set your meter to diode test and test out D3 and D4? Should be around .4v to .6v.

Actually would be quick to test out all the diodes on the power supply.

Is P2 a new part? I'm surprised you don't see that testing as a short. Did the game ever work for you? Just trying to see if the problem occurred after a board repair or not.

The pictures of the board being upside down and then turned the wrong direction, have been giving me problems. I am actually thinking the P2 is installed backwards, as - should be where + is and vice versa. P2 (-) should be going to the (-) sides of the both of the big 10000uf capacitors.

When you remove or look under P2, I hope there are some markings on the board showing where + and - are on P2 when installed.

Alrighty, glad something is making more sense now. I should had looked at the drawing for part orientation.

I definitely would change the capacitors since the game was fired up with them backwards

Glad to hear it is booting up now.

F4 fuse is for the 39v coils. I would test out P4 as you did with P2. If P2 tests ok, then inspect and measure all the coils on the underside of the playfield and the one under the apron to see if you have a shorted coil. If you find a shorted coil, you definitely have a shorted transistor causing the F4 to blow.