Selector switch on Bolex 18-5

[Kirk Anderson]

Shane Collins wrote in a different thread "there are reports of the [18-5] selector switch going bonkers. Apparently this switch can't be fixed. The issue seems to be the inability of the selector switch turning on the lamp itself."
Well, that's where I am. I was able to isolate the problem today. By putting a jumper across the right contacts, I made the lamp come on for the first time since I acquired this machine (regular 8mm). Contact cleaner has not solved my problem. I believe that we're dealing either with oxidation, or a spring that got tired, and perhaps both. But I have the service manual, and the diagram for this assembly is worse than intimidating (pp. 23-24 if you downloaded the same pdf as I did). Has anyone on this forum ventured inside? FWIW, mine has the round dial with white glow-in-the-dark knob.

[Kirk Anderson]

For the time being, I am running a jumper wire from the transformer to the bulb. The only drawback I can see is that the lamp comes on when I'm threading. I might install an auxiliary on/off switch.

[Shane C. Collins]

It's interesting that no one has ever figured this out! My hunch is the wires, and other connections behind the selector go bad, or as you mentioned, get oxidized. When I first purchased my Bolex 18-5L Super the bulb would not come on. So I tried all the little tricks I've tried before to get things working. This included spraying the contacts below the bulb, and the area where the bulb fits into the assembly. Also unscrewed the selector switch, so I could peak inside. I ended up spraying behind the switch. Whether that did anything I'm not sure to be honest with you. Then after the cleaner dissipated I was able to get the lamp to work. But this hasn't worked for everyone having issues with the original Bolex 18-5 and it's Super 8 variants. I know I've read people with this problem have dumped the offending machine, and purchased another online. It really would be in everyone's best interest for someone to dig in and solve this problem once and for all.

[Kirk Anderson]

Agreed! And thanks for your insight. The contact cleaner spray didn't help, and I'm apprehensive about disassembly. Have installed a jumper wire, and new switch on the lower housing. Waiting for new bulbs to arrive, as I am converting this to halogen.

[Kenneth deGruchy Jr.]

I just went through this with my first regular 8mm Bolex 18-5 with the 8.5 volt, 50 watt spaceman lamp. I took apart the rotary function switch only to find that the contactor that completes the circuit to the lamp was not making contact. The contact did not appear to be dirty however the plastic mounting base it was loosely riveted to had deformed or melted due to overheating definitely caused by a poor connection that acted like a hot resistor. Maybe before the overheating there might have been oxidized or a dirty contact that led to the problem. Now how to fix the problem? It looks like the contact with it's plastic base may be replaceable but since there are no parts available a parts donor would be needed. I was considering asking a buddy with a 3D printer if he could scan and then print a new base that I could affix the original plated metal contact and mounting rivet to. That plan has gone nowhere so like you I jumped the lamp contact wires to get the lamp to operate. Clearly the lamp switch is poorly designed for the purpose of actually operating the lamp. I would mod the projector to use a relay to actually supply reliable full current to the lamp and thereby take the stress off of that rotary switch.