8mm Forum: Very Strange

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Posted by Bradford A Moore (Member # 426) on January 09, 2015, 10:40 AM:

Last night during my Thursday night film series I was showing a super 8 print of The Blue Angel (1930), when I started to thread the third reel on my Elmo ST 800, the lamp wouldn't go off in the off position, and burnt two frames. Luckily it was still the leader and no film lost. Still a bummer though. I hate to damage a film, which will now need to be spliced, and had been like new.

I had to stop the show for about ten minutes or so to try and fix the problem. I almost thought I would have to cancel the rest of the show. I was pleased that I didn't have to. I unplugged the projector, and took off the forward and reverse nob, and while turning its spindle back and forth I was able to spray some air into it, which may have loosened up any built up dirt which may have been making it stick.

The rest of the show ran smoothly from there. With all my years showing films that has never happened. My first thought was that my motor belt had snapped, which had happened before. and was during a showing of Girl Shy with Harold Lloyd. I did loose a frame that time though. Last night my audience was very understanding which helped a lot. Looking back on it now I can understand why it happened last night, and will clean that out more often from time to time.

Posted by Steve Klare (Member # 12) on January 09, 2015, 10:56 AM:

Welllllll....

This is your lucky day! (sort of...)

I had this exact problem with mine about five years ago and I can tell you exactly what to do about it...but it aint pretty!

Your selector knob actually rotates a camshaft. The lobes of the cams depress different lever switches. Two of them select your motor direction, and one of them turns the lamp on and off.

On mine the lamp switch stuck "on", even after the cam was allowing it to turn the lamp off. It would eventually let go and it was OK for a while.

Suitable switches are available brand new from many sellers, and they aren't expensive.

The problem is the surgery involved. These switches go behind a plate. They are layered three deep and each has an insulator to the next.

Once you find the switch to replace, you have to solder in the new one and restore this stack of stuff!

I tried putting the layers in place and then putting in the screws, but the holes kept moving around and it became like herding cats.

After I reminded myself I enjoy this hobby so much I started with the plate and the screws, built the stack up on the screws, and then flipped the assembly over onto the camshaft and tightened it down.

-five years: no trouble.

I had this problem on and off: I can pretty much guarantee yours will return. My idea what happens is the lamp switch contacts are so burnt up the current is flowing through a small surface area, and when the surge from the lamp hits, you are actually getting a spot weld. Since it's not a great weld, often it fails, but here and there....

The operative consideration here is can you solder, beyond that it's mostly a matter of patience and persistence.

[ January 09, 2015, 02:57 PM: Message edited by: Steve Klare ]

Posted by Steve Klare (Member # 12) on January 09, 2015, 08:06 PM:

Hi Brad,

I received your PM. It is only a fragment and the system told me your inbox is full when I tried to reply.

I am pretty sure this is the problem. For one thing this mechanism is on the opposite side of the machine's main chassis and although I could imagine some foreign object making this happen, I can't see how your blast of air through the knob opening got to it.

You can run the machine really carefully for a couple of weeks and see if it happens again or not. Basically don't stop the machine with film in the gate and the lamp lit, and when you dowse the lamp at the end of a reel, if the lamp stays on don't stop the transport until the gate is clear and then yank the power cord so you don't run the lamp without cooling air.

-after a while you'll know one way or another.

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