Hi guys,

I have a Tron pro machine and it has been working solidly for years. Recently though the upper left flipper locked on and blew the fuse.
I replaced the transistor with an IRL540N and changed the diode that sits next to it on the board.
When I turned it back on the flipper stayed down, i flipped it once and no issue, then i flipped it again and it locked on and blew the fuse again.
I checked the resistance across the coil (disconnected) and got a reading of 4 ohms, as far as i understand it that means it is okay.
So i have changed the transistor and diode on the driver board again (Q12 and D12) hoping that it was a bad transistor i had put in. When i turned it back on the exact same thing happened. Flips for one press of the button fine, then when you press the button again it locks on.

What am i missing? its driving me spare because it takes me ages to change transistors.
Any help would be great.

Thanks,
Eric

Thanks for the tips. I did what you suggested.
I actuated the flipper 5-6 times before pressing the button. I measured the voltage between the ground and the flipper plate (I was getting 0.2v across it and the two bottom flippers). I even changed out the coil on the off chance that it was somehow at fault.
Nothing happened when i moved it by hand. During gameplay the flipper worked normally for about 10-15 flips this time and then locked on and blew. Now as soon as you turn the game on it locks on.
I am out of ideas. I have changed the coil and the transistor and the diode and its is still blowing. I can't find any bare or touching wires anywhere inside the cab. The board looks clean too.
Any suggestions?