I needed a couple replacement bulbs for some Nishijin machines (a 1969 single shot and 1978 model C). I decided to order a 10 pack LED E10 bulbs. I run my machines on rechargeable 9volt batteries and though generally I'm happy with the battery life, I figured LEDs would give me even more time between charges. Mostly they're fine and get the job done.

But they won't work at all in the upper right jackpot light on my model C. I tested the bulbs in other spots and they work fine, so it's not the LED bulbs. With a regular filament bulb in the upper right corner, the light works normally, so it's not the wiring or a switch or anything like that.

Any idea why LEDs wouldn't work in that slot? I tried gently crimping the bulb holders thinking maybe something just didn't jive with the newer bulb bases, but that didn't help any.