I have one single playfield lamp not working. I replaced the 1n4004 diode at the lamp base, tested the circuit by bypassing the base altogether to rule out bad weld joint in the base itself. If I put a bulb from the input wire directly to ground it lights and stays on constantly. The partner lamp that shares the other phase of the driver transistor (Q28 in this instance) works just fine. I've ruled out the driver transistor, the lamp base, the 1N4004 (replaced with 1N4007), multiple incandescent bulbs, and nothing works.

Fyi, it is a Special Force machine, the Upper Left "FIRE" light isn't working. Per the manual it is on Q28 and shares that transistor with "Bomb 4". Again, aside from a few of the GI lights, this is the only active playfield light that doesn't work. What else could it be?

Thanks!

I had this issue occur four times on two Bally 6803 machines. I can't remember for sure but there may have been a typo in the manual with incorrect pairing of the lamps. A google searched brought up the correct lamp-transistor assignments. If I can find it I'll send you a link. Are there any other nonfunctioning lamps out that, according to the manual DON'T share the same transistor as the lamp that in question? If so then this may be the issue. But if I remember correctly I simply daisychained my "FIRE" lamp to the generic unlabeled lamp directly underneath it (the one that flashes to simulate a launched rocket). This way they both go on at the same time instead of a split second after the other. Pretty sure I gave up on this one.

^^^^^ IGNORE THIS POST IF YOU HAVEN'T READ ALREADY AND READ THE NEXT ONE BELOW!

Go to this site and look at the TECH CHART for Special Force. The PDF has the correct transistor assignments (the manual, mine anyways, was incorrect).

I REMEMBER NOW! This indeed was the issue. Turns out in reality the upper left "FIRE" lamp was on Q36 which is partnered with a general illumination lamp. I had a few GI lights out in nonvisible areas and it never occurred to me that a playfield lamp could be partnered with a GI lamp (Very different from Williams design!). Sure enough the GI light and the FIRE light on Q36 were both out. Changing this transistor fixed the issue. Lesson here is if ONE playfield light is out it's pair might be a GI lamp, so look for nonfunctioning GI's too. Hope this helps!

Here's the link:

http://www.pinballrebel.com/pinball/cards/