This was a quick fix as I've seen this issue before. So I was working on a Data East Laser war pinball machine, and some of the flashers were stuck on. This pinball machine just had all of its bulbs replaced with LEDs, so realistically there shouldn't have been a problem. There were also several stuck on so it was more than just a bad socket or a wiring issue. I identified the bulbs as the following:
Flashers are driven by the solenoid circuits, so it seemed odd that the flashers were for solenoid drivers 6, 7, and 8. Looking at the schematic, I could see that the ones in question all had a warming resistor. What a warming resistor does is that it provides a current to a bulb that is less than what is necessary for it to glow. The idea is that it makes it a little bit quicker to warm up and flash than it would be from a cold start. This can be represented by the highlighted resistors below:
LED bulbs do not need these warming resistors as they require not only a lower amount of current to flash but because they are LED they turn on much faster. Not even all the flashers have these warming resistors as I pointed out.
The solution here was literally to just remove the 660 ohm resistors from circuit. After removing them, they turned off as they should and even flashed as they should.