Quoted from kbliznick:

this one is cake. Simply remove the 330 ohm warming resistors from all of the individual boards. These can stay off the game even if you put incandescents back into the game. Williams got rid of the warming resistors starting with Big Guns yet they didn't change anything else in the circuits. They moved all the resistors to 1 board and then a couple games later they put them all on the interconnect board.
The trickier problem is when putting flashlamps into games that had the Aux power driver board (again starting with Big Guns ). On those games if you put LED flashlamps into circuits #3, 4, 6 or 7, those flashlamps will go off anytime you hit the flippers or any other 50 V coils. On those circuits you would need to cut diodes 3,4,6 and 7 off the aux driver board and then install diodes on coils #3,4, 6 and 7.

Quoted from kbliznick:

High Speed doesn't have an Aux driver board so you don't need to cut diodes and add diodes. You just need to removing the warming resistors
It has little boards with 2 power resistors soldered to them. The 10 ohm resistor is needed to achieve the correct voltage. The 330 ohm "warming" resistor is the one that is bleeding the current through. Cut those from the boards (test it out with 1 before cutting the rest). I believe HS has all 6 volt bulbs in it (#63) Did you buy 6V flash bulbs or do you have 12V bulbs? I usually rearrange the flashlamp circuits and change the sockets from being wired in series (6V) to being wired in Parallel (12V) and then you can use the standard 12V bulbs.

Quoted from kbliznick:

Which flasher's? All of them? Don't think I've seen this (other than on CFTBL which I've never had the time to figure out)
On the boards with Aux driver boards it's leaking voltage from the 50V to 25V circuits which cause it. On High speed there are NO computer controlled 50V coils for the voltage to bleed from. There are 50V coils in the game but they are turned on by the computer controlled 25V relays.

Quoted from GRUMPY:

You can try replacing the diodes on the flipper coils.

Quoted from GRUMPY:

If you get some 1n4007 diodes you can you them on the coils, lamps and switches. You can use them anywhere a 1n400x diode is used.