Bolex 18-5 light issue

[Paul Winter]

Bolex 18- 5 light issue ..... I have managed to rectify many other small faults on this projector ie drive belts drive to front arm etc , but cannot seem to get the bulb to work I put a test meter on the bulb and that seems to tell me it’s ok and viewing under a magnifying glass sees the element intact

I have tried to take power readings from the two red cables supplying the power to the lamp when the switch is on but see nothing ? Is this a/c current or D/c and should I see a reading here ? Ie as the both supply cables are red is it just a continuity current ? Is there any other way to check the bulb ? As the voltage is so low in the bulb not sure the best way to do this ? I have checked the transformer and the two red cables on the bottom left doesn’t show a current Should It ? Does anyone has a service sheet for this projector showing how to check voltages on this huge transformer lol

Any help or guidance appreciated regards a Paul

[Shane C. Collins]

Have you tried cleaning all the contact areas? Take of the red wires and spray some contact cleaner. Also spray cleaner inside the bulb socket. You may also want to investigate the selector switch and try to spray cleaner in that area. The selector area is pretty well sealed but it doesn't hurt to see if any contact cleaner soaks in that area. You can loosen the screws that hold the switch plate and get a better look inside the selector itself. There are multiple connections inside there that could be tarnished. Which model variant is this 18-5? Regular 8mm or the later Super 8mm machines?

[Joseph Banfield]

If you measured voltage at the transformer and found none then there is no point in checking switches or contacts since all that stuff comes after the power transformer. I assume the projector was switched on when you took voltage readings at the transformer? The meter should be set to read AC volts. I'm not sure which model you have but you should be looking for 8 or 12 volts at the transformer, depending on which lamp it uses, which should be marked on your machine somewhere.

[Shane C. Collins]

The first series 18-5's (regular 8) used 50 watt lamps. The first 18-5 Super 8 machine used 50 watts. The last versions of the 18-5L Super used 75 watt halogen bulbs.

[Paul Winter]

Sorry for the late reply ..... projector now working after following all the key points raised thank you .... just a query though I have got a couple of dead bulbs in the box, and when put in the projector they don’t work obviously, however when you take them out and do a reading they show good? Even when looking with a magnifying glass the filament inside are good so why don’t they work in the projector ? Is there another circuit ie a heating element that you can’t see causes them not to work?

[Paul Winter]

Well I am back to square one but don’t know why .... had a new bulb delivered today so fitted that turned on no lamp?

removed bulb , checked voltage , no voltage ? Took switch assembly off sprayed with cleaner and also on the wiring side, blew out with clean air assembled it still no power at lamp terminals ? .. took transformer off to check that wire had not been trapped or burnt all Ok ? Tried to jump a wire across the two red terminals at switch with power on for lamp nothing ? Jumped two wires direct from transformer to bulb and bulb lights up ? .... any ideas ? To me, it’s either the return to the transformer or the switch bit don’t understand why the lamp doesn’t work when jumped across the two switch wires UNLESS the switch feeds another supply somewhere which allows the projector to allow the light to work .... Mmm got me this one ...

[Nantawat Kittiwarakul]

OK first thing first. Does the transformer supply correct output voltage (8 or 12 volt) right? The lamp does light up if directly connected to the transformer correct?
If that's the case then it's definitely loose connection somewhere along the line, can't be anything else. The rest is to find that out, easy task.

[Lee Mannering]

Paul. Have you checked for a blown fuse?