The resistor is called a "warming resistor", it keeps some current flowing to the bulb and keeps it warm. If the bulb had to take the full load when it was cold the bulb would burn out. Snip one leg of the resistor at the mid point and let it hang and try it. I had to do it to my Space Shuttle for the flashers to work properly. But please wait till someone with more experience confirms this. I've only done this once but I think I'm rite.

I believe you need to clip/ remove the big under playfield resister (can't remember the size off the top of my head. Williams put the big resister under the playfield because a small amount of voltage is always applied to the lighting circuit so the regular incandescent bulbs could respond faster to input when they are activated. Without the small amount of constant current the regular bulbs didn't react (turn on) fast enough during gameplay. The resistor is there to stop the regular incandescent bulbs from glowing from the current. LED bulbs on the other hand are always on, or off without any dimming capabilities, that's why your bulbs are always on. If you can get a copy of clays repair guides, he talks about the big resistor and what it does.

Yep. Warming resistor. Keep incandescent filament warmed up. You should be able to see a slight glow on the incandescent filament when the machine is on. If you don't, you either have a blown bulb depending upon the game, (multiples on the same circuit are wired in series), old bulb that needs replacing or bad warming resistor (very common.) Warming resistor provides for brighter flashing and extends bulb life. With the warming resistor installed current is always flowing to the flash lamp socket - enough to turn on an LED. Remove it to make a LED work correctly. You can just cut it off as even if you would ever want to go back to incandescent, its best to go to a 5w resistor. Last one I changed literally fell apart in my fingers it was so bad.

viperrwk

Are you able to send a picture of this please.

I clipped the end of the warming resistor attached to the black wire and now my LED flashers don't fire at all.

http://img-f.pinside.com/201405/1663301/236027-i.jpg

Picture courtesy of Jumping-Box on the other FP thread.

Is this a 1 ohm 1/2w resistor for the firepower flash lamp board? I know the big one is 330ohm.
thanks!

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Thanks Schwaggs! Talking about a needle in a haystack. Amazing amount of dead stuff on the 37 yr. old firepower.