Sigh, so much confusing information...

Read this.. http://techniek.flipperwinkel.nl/wms11/index2.htm#flash

Then you have 2 choices if you wish to use LED flashers.
1. You remove the 330W resistor (lifting a leg is fine, remove the ground wire is fine) or,
2) You leave incandescent flasher in the backpanel and only do the upfacing ones on the playfield.

I did #2 to my F-14.

What is happening is that 330ohm resistor is causing a constant current drag to ground while the lamp is off. This in turn cause a small amount of voltage to be present at the point where the 2 resistors are tied to one leg of the bulb. This in turn causes the bulb to 'warm' or be in a state not off but not on enough for you to see it. That way when the logic says FLASH, the bulb is already half way there.

The resistor does not limit voltage and removing it will hurt nothing even with incandescent, however regular bulbs will ramp up and down and not be as flashy. Not what you want from a flasher.

The reason you have to take it out is the LED bulbs are either on or off, not warm, and that small voltage being placed at the mid point between the 2 resistors is causing LED bulbs to be ON.

The reason option #2 works is because for every flasher on the playfield, their is another 'paired' with it on the backpanel. And that 1 incandescent has enough load to pull that small amount of voltage the 330ohm resistor is causing down low enough that the net result is its LED partner stays off.

I use option 2 all the time, that way 0 mods to the machines wiring. It works on DE/Williams/Bally and any machines with 'paired' flashers.

And in my machine, I did not. That way I did not have to remove warming resistors.