8mm Forum: Bolex 18-5 Projector Bulb Problem.

This is topic Bolex 18-5 Projector Bulb Problem. in forum 8mm Forum at 8mm Forum.

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Posted by Joe Geiger (Member # 6893) on March 11, 2019, 03:09 PM:

Does Bolex 18-5 projector have a feature that prevents the bulb working if the film feed/reel axle drive is not working. This could be a feature to prevent burning the stalled film. Projector had not been used for a few years while and when i went to use it I found it had only one of the three drive belts and it was also broken. So the film wheel and reel axles were not gong to work. Waiting for new belts to be delivered.
Projector bulb would not light. Tried another bulb and it didn't work either.

Posted by Janice Glesser (Member # 2758) on March 11, 2019, 04:13 PM:

Hi Joe and Welcome to the Forum. If you have a multimeter you can test to see if power is getting to the lamp socket. If your model is using the old "Spaceman" CXR bulb...Corrosion can build up on the socket connectors and prevent the flowing of electricity. Try cleaning with some Dioxit or scraping any visible corrosion. If your model is using the newer M16 bulb try inserting the bulb and removing it several times to clean out any corrosion in the socket.

Posted by Joe Geiger (Member # 6893) on March 11, 2019, 05:38 PM:

Thanks for suggestions Janice. I had already tried your steps after finding out about those problems from my google search.
The new belts came in the mail today. I'll put them on and see what I get.

Posted by Janice Glesser (Member # 2758) on March 11, 2019, 07:56 PM:

Does this mean you're tested the power to the socket?

Posted by Joe Geiger (Member # 6893) on March 11, 2019, 10:01 PM:

With no bulb in the socket I measure 8.8 volts AC but when I put the bulb in and measure at the prong at bottom of bulb and ground there is 0 volts. If I lift the prong off the bulb I again get 8.8 volts. That seems strange to me.

Posted by Brian Fretwell (Member # 4302) on March 12, 2019, 03:35 AM:

Sounds like there is a high resistance somewhere (usually where there is a corroded join) and the current is dragging the voltage down when on load. You will need to check all joins on the wiring between the transformer and the lamp holder.

Posted by Joe Geiger (Member # 6893) on March 12, 2019, 09:59 AM:

Yes to the bulb socket.

Posted by Joe Geiger (Member # 6893) on March 14, 2019, 12:07 PM:

I got the new drive belts installed and reel axles and film feed run okay but bulb still no light. Based on changing voltages I am reading at the bulb socket I was also thinking corrosion at a some contact. Also the projector has sat idle/stored for several years which is when corrosion cold occur.

I have checked all wiring connections that I can see after removing various covers and they look good. I am getting 9 1/2 V AC off the two red wires at the transformer and that apparently supplies power to the control switch and bulb. The control switch contacts are difficult to get to inspect/clean. I have taken the switch assembly loose from the projector body I tried to clean the switch contacts using a electronic spray cleaner and working the switch back and forth but so far no success with that. Any other suggestions?

Posted by Janice Glesser (Member # 2758) on March 14, 2019, 03:07 PM:

I'm assuming your projector is the standard 8mm that uses the incandescent 8V/50W CXR bulb? Is that correct? There was also a 18-5 Super (super 8mm version) that used the same CXR bulb. The updated 18-5L Super 8 version used the incandescent CXL bulb prior to 1970 and then the halogen EFN. These were both 12V/75W bulbs.

Have you tested the bulb(s) to see if they are good. I have experienced problems like this and discovered the first two bulbs I tested were bad. It can happen [Smile]

It wasn't until I tried a third bulb that it worked. If you are getting power to the socket the bulb should light.

I've found on the Bolex 18-5 there can be a power drop after threading...but this is normal.

[ March 14, 2019, 04:25 PM: Message edited by: Janice Glesser ]

Posted by Joe Geiger (Member # 6893) on March 14, 2019, 10:06 PM:

Janice, You have been very patient with me and i appreciate your help.
Yes my projector uses the 8V/50W CXR bulb. I can see no damage to the bulb wire elements and all three bulbs that I have measure 0.3 ohms resistance so they should be okay. I have tried only two of the bulbs so far saving the 3rd to check only after I do some more troubleshooting.

As I said in earlier reply, The voltage I measure with the bulb in socket is Zero and then when I lift the prong off of the tip at bottom of the bulb the voltage goes to up to 4.8 - 8.8 volts with different measurements. This I find really strange.
Joe

Posted by Terry Sills (Member # 3309) on March 15, 2019, 02:27 AM:

Logic would say that if you are getting the correct voltage at the socket, then the bulb must be faulty. I find the easiest and most reliable way to test a bulb is with a 'glow' test, by just putting a lesser voltage (4 -6v) through the bulb. If the filament glows it proves it good. Always a better idea to check the simple things first, but make sure the bulb's prongs are free from corrosion, by scraping with a small knife or with emery paper.

Posted by Brian Fretwell (Member # 4302) on March 15, 2019, 03:17 AM:

If the bulb is bad surely it wouldn't have such a low resistance, he says 0.3 ohms, when the filament is cold. The only way to test would be checking how much current is drawn when the lamp is in circuit and that would be very difficult without removing wires to insert the meter.

Posted by Shane C. Collins (Member # 5641) on March 15, 2019, 08:29 AM:

Did you try squirting some contact cleaner inside the bulb socket? I had a problem similar to yours, and after using some contact cleaner the bulb worked. Those sockets can corrode very easily when a bulb sits inside the projector for many years.
Also I have found on my Bolex 18-5 Super the bulb doesn't always light right away. I have to work the forward switch a few times and it comes on. The selector switch on these projectors can also corrode. But as you found out it's almost impossible to get inside one because of the way it's constructed. I dissembled my switch in the same way you did, and tried to squirt contact cleaner inside the switch the best way I could.

Posted by Joe Geiger (Member # 6893) on March 17, 2019, 08:06 PM:

I am still troubleshooting my Bolex 18-5 projector - bulb won’t light. This projector is a circa 1966 model with Serial No. 2112721. Projector had been in basement storage for many years but worked when put away.
I have cleaned/emery papered all accessible contact points. I am getting 9.5 volts ac at transformer taps that have the heavy gage red wires going to selector switch & bulb socket and bulb socket ground. With selector switch in position for lighting bulb I was only getting 4 ½ to 5 volts ac at bulb socket with bulb removed which indicated maybe corrosion on selector switch contacts. I then jumpered the 9 volts off the transformer contacts to the bulb and the bulb lit good and bright.
As I said in earlier note, I removed contact switch as best I could for access to switch internals and tried cleaning switch contacts with electronic spray cleaner. No improvement. Then I sprang for $28 12 OZ spray can of “NoFlash Elecltro Contact Cleaner” advertised to remove dirt, moisture, flux and oxides and sprayed switch internals again working selector switch back and forth several times. This cleaning seemed to work as then I got 8 ½ - 9 volts ac at the bulb socket with selector switch turned to bulb position. But when I installed the bulb it still would not light.
Bulb socket is not threaded but uses CXR, 8v-50W bulb with flange disk for ground and tit on the bulb bottom that contacts sprung strip tab bringing power from the selector switch. Strangely with the bulb in the socket the voltage at socket is zero but if I pull the sprung strip tab off the bulb tit the voltage goes back to 8 ½ to 9 volts ac. I am puzzled as to why the voltage goes to zero when all the contacts are made.
Also, can somebody tell me, what is the purpose of the can capacitor that is mounted behind the transformer?

Posted by Maurice Leakey (Member # 916) on March 18, 2019, 04:41 AM:

Joe
Whilst I cannot help with your lamp problem I might be able to give a comment on the capacitor.
In the early days projectors quite often caused interference with radio and television reception. So suppression capacitors were wired across the mains with a centre tap to earth (ground).

Posted by Joe Geiger (Member # 6893) on March 18, 2019, 02:15 PM:

Thanks Maurice.

Posted by Joe Geiger (Member # 6893) on March 29, 2019, 09:01 PM:

I appreciate all the comments and help on my bulb lighting problem. I have had to stop working on the problem as I am in the process of moving to another state. I will resume my efforts after I get resettled to open selector switch to check contacts for corrosion and clean, if needed.

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