Hello, I recently picked up a sf2 machine. This machine had 1 existing problem on it. The right kicking rubber was not functional. I noticed a new coil had been installed. I found the f17 fuse blown and replaced it. Upon testing, the fuse instantly blows. I disconnected the coil and replaced the fuse. I then tested with a meter while firing that coil. I'm getting about 72vdc when I activate that test output. I figured maybe the coil is bad so I disconnected the left kicking rubber that was working and jumped the right kicking rubber wires to the left coil. Again the fuse blew. I then put the wires back on the existing left coil (which was working) and now that f16 fuse blows. I then replaced the driver board , both coils (a-5195) , and 2 1.5 amp slow blow fuses. Again they both blow when solenoids activated. No clue where to go from here. Please help.

The fuses only blow when connected to the coils. I guess you could call them the slingshot coils. The manual and diagnostics refer to them as kicking rubbers. I am wondering if the voltage is too high. The schematics say I should have 48vdc. I have 72vdc.

I don't think it's the wiring. The fuses do not blow until the coils are told to fire.

Ok after reading the above post, I checked to make sure the polarity was right on the coils. The left one was ok but the right was backwards. I flipped the wiring on the right coil. Now when you install the fuse on the left sling or right sling, the 72vdc on the fuse block under the playfield drops out to nothing and the service switch wont register. It's like I'm getting a back feed on the board screwing up the switch inputs.

So I figured out what it was. Thank you to everyone who posted especially crlush. It was checking the polarity for the diodes on the coils that led me to the solution. Apparently wiring coils backwards ruins the diodes and even though my driver board was new, it damaged the 2 transistors on the outputs. To fix the problem I took the old driver board and replaced the 2 transistors. Then I took diodes from old coils I had and put them on my current coils. When I did that it worked. I guess originally whoever owned the machine before me, put a new coil in and had the polarity wrong and blew the diode. Then it just snow-balled into a mess when I crossed polarity on the other sling. This was a big learning experience and I wasted $150 in parts that I didn't need. From now on I'll check every coil with an ohm meter before installing to make sure the diodes are good. I never imagined having a crossed polarity would do so much damage.