Variable Speed Control Fix

[Shane C. Collins]

So recently, while projecting a print on my Elmo FP8-C, I discovered the speed was wonky, and changing up or down. At one point the film came to a complete stop. Needless to say it left me scratching my head. For one thing I recently did a complete belt change, and lube on this machine, so I knew it wasn't that. So today while cleaning the projector I decided to check the variable speed control. The Elmo has an access panel underneath which unscrews, and allows you to check the switch etc. Upon inspecting this variable speed switch I noticed lots of green corrosion. The speed switch on the Elmo FP Series machines looks like a large porcelain resistor with a sliding metal conductor. The switch slides from one end to the other, and this changes the speeds from 14-24 FPS. The metal that is embedded in the porcelain looking material was all corroded. So I decided to use some contact cleaner. I sprayed the whole switch and all contacts, and worked the switch back in forth. After doing all this the switch, and speed of the projector is perfect again. So if your having wonky speed issues on an Elmo FP Series or other projector the variable speed switch could be the issue. I'm including some photos of where the speed dial is located, and a look inside the projector where I fitted a Bolex 1.3 15mm prime lens for anyone that's interested.

[Nantawat Kittiwarakul]

Cracky audio volume pot., on massive scale.

[Joseph Banfield]

Yes, many companies used that type of speed control which is known as a power rheostat. In many cases they are not very reliable because of the high heat they generate in operation and often simply go open circuit after a time depending on the quality of the materials used in the rheostat. You're lucky it was only corrosion that needed removed...I wasn't so lucky with a Pathè projector a few years back with several broken windings along the porcelaine tube!

[Shane C. Collins]

Thanks Joseph! The one in my projector looks similar to this one. I have a spare projector so should this one ever go, I'll have a replacement. They look pretty durable overall.

[Joseph Banfield]

Yes, that is the durable version you have pictured. Some machines use a long porcelain tube wrapped in very fine resistance wire with a sliding contact. Those are the ones that fail constantly and were never up to the task to begin with.