UPDATE: I am posting an "idiot's guide" on how to do this at the end of this post. It certainly works for Dr. Dude and -should- work for other System 11c games too.
When I hit the flippers on my Dr. Dude, about 5 of the flashers in the game pulse dimly for a brief moment. Not all the flashers, just 5 of them. All flashers in the game are LED.
I read that this is a known issue in System 11 games. The solution I found was to remove 4 diodes from the aux power board and add diodes to a few coils. I just need some clarification before I do this....
1) These diodes are the ones located on the power supply (top right) with the big heat sink, correct?
2) Does it matter if I clip them off or desolder them?
3) Are the diodes I removed from the power board the same ones I'm adding to the coils?
4) Does anyone know where the diodes go and on which coils on Dr. Dude? I found instructions for Whirlwind but obvious using different coils here.
OK - here's the idiot's guide to getting LED flashers to work properly on Dr. Dude and other System 11c games.......
1. Purchase 1N400x diodes on Amzn. The "x" can be any number. I used 1N4001 but the others work too. You can get 50 of these for $3 shipped. Good to have on hand.
2. Find the aux power board in the backbox. It's located near the middle of the right side, BELOW the power supply (power supply has large heatsink). Find the diodes labeled D3, D4, D6, and D7 (diode = small wire with the black thing in the middle) on the aux power board. They are all next to each other vertically. Use a wire cutter to completely remove those four diodes I just mentioned.
3. Now find coils 3, 4, 6, and 7 under your playfield. If you have no clue which those are, grab the manual for your game and find the solenoid table, usually found towards the beginning. In the table, you will see the Solenoid # (i.e. the coil #) and then the function describes what it is so you can identify it. In Dr. Dude, you want the Ray coil, Gab coil, drop target coil, and knocker coil (you can skip that one if you disconnected it).
4. Solder a 1N400x diode to each of the above coils, with the gray banded side of the diode attaching to the power wire lug (power wire is the thicker wire of the two attached) and the non-banded side attaching to the other lug.
5. Install your LED flashers, start a game, hit the flippers. No flashers should fire. There you go!