Variable-Speed Projector verses varying the input voltage on Fixed-Speed Projector

[Alwyn Adkins]

Lately a few variable-speed projectors have come up on Facebook Marketplace.

In my current setup, I have a Eumig fixed speed (18/24) projector connected to a power supply that I can vary the voltage on, thereby lowering the speed of the projector to eliminate flicker, which works reasonably well for my telecine "direct-shooting" workflow. Over multiple sessions (including days) 194v will give me no flicker (220-240v power circuit), and it will hold that nicely for the length of a big reel.

A couple of questions:

How well do variable-speed projectors hold their speed to prevent flicker?

Would this be a better option than my current setup?

Thanks for any input you may have.

[Ken Finch]

I use a similar method with a Eumig 810 d which works quite well. Just have to tweak the voltage back a little as the projector warms up.

[David Strelitz]

On an 8 series Eumig, by setting the internal adjustor to 60 cycles, you can now slow the speed controller below 18 as there is more traverse, and achieve 16.666 FPS which on the 3 blade shutter will be strobe free.

[Alwyn Adkins]

Thanks very much David, I'll check that out when I fire the Eumig up again soon.

[Nantawat Kittiwarakul]

Those silent projector with variable speed function, is likely to be DC or universal motor type. Both can have is speed gradually adjustable electronically.

But here's the catch. Its speed will NEVER stay fixed. It can (and will) drift away from the first set speed due to several factors - input voltage, temperature, mechanical load, belt slip, etc., and the list goes on and on.

When used as intended (showing silent films to audience) this will never be an issue as its speed fluctuation / drift will be almost unnoticeable to naked eyes. But when pairing with camcorder (which need rock - solid speed) it will be quite an issue. In the best case scenario it would appear as just a faint banding that slowly moves up / down, almost unnoticeable. But in the worst case scenario it would be so bad that you'll have to babysit & keep adjusting its speed throughout the telecine process - not a fun experience at all (been there, done that).

However if possible try searching for SOUND projector with adjustable speed function. As most sound projector would have better speed regulation needed for sound reproduction. Certain make & model might be "good enough" for telecine work.

[Alwyn Adkins]

Thanks Nantawat. Variable speed sound projectors are very hard to come by, but will keep my eye out.

[Tim Gillett]

On an 8 series Eumig, by setting the internal adjustor to 60 cycles, you can now slow the speed controller below 18 as there is more traverse, and achieve 16.666 FPS which on the 3 blade shutter will be strobe free.

I think this is the same setup as with the older Eumig 710D sound projector which I have owned since the mid 70's. These projectors used an AC motor whose speed was proportional to mains frequency. The proper way to vary motor speed while maintaining regulation would have been to vary not the input voltage but input AC frequency, which wasnt straightforward so I never attempted it.

Instead I did what you did, adjusting the little metal flag inside to 60 Hz and then sliding the 18/24 speed slider on the front panel to the appropriate speed, effectively altering the gearing ratio to achieve approx 16.666fps for telecine with an interlaced 50i video camera.

But these Eumigs while well built eventually had problems with the rubber hardening on the two internal drive discs, requiring cleaning, then roughening up to prevent slippage, then finally complete rerubbering of the metal discs. Also the audio output had a fair mains hum component because of the pick up head's close proximity to the large mains transformer and the large AC motor.

As I may have mentioned on this forum earlier I got tired of these problems even when using other 8mm sound projectors, so I modded a semi pro Revox tape machine to play just the 8mm film stripes. The hope is to one day further develop the same machine for capturing both picture and sound on 8mm films.

[Tim Gillett]

Thanks Nantawat. Variable speed sound projectors are very hard to come by, but will keep my eye out.

Later model 8mm sound projectors mostly changed over to low voltage DC motors with electronic speed regulation to achieve the two film speeds. While most didnt have front panel variable film speed, normally inside the projector are two small speed trimmer pots preset in the factory for 18 and 24. For telecine I just adjusted the internal 18 fps trimmer to approx 16.666 fps. On one projector I drilled a hole in the back case panel to allow adjustment of the 18fps trimmer with a small screwdriver without having to open up the projector.

[Alwyn Adkins]

Arr, great, thanks Tim!

But these Eumigs while well built eventually had problems with the rubber hardening on the two internal drive discs, requiring cleaning, then roughening up to prevent slippage, then finally complete rerubbering of the metal discs. Also the audio output had a fair mains hum component

I've found exactly the same with my 820.

[Brian Fretwell]

Later model 8mm sound projectors mostly changed over to low voltage DC motors with electronic speed regulation to achieve the two film speeds. While most didnt have front panel variable film speed, normally inside the projector are two small speed trimmer pots preset in the factory for 18 and 24. For telecine I just adjusted the internal 18 fps trimmer to approx 16.666 fps. On one projector I drilled a hole in the back case panel to allow adjustment of the 18fps trimmer with a small screwdriver without having to open up the projector.

I did similar to my Sankyo 301, many years ago, 16.666 for silent 25 for sound. That was in the days before solid state camera sensors!!!!

[Tim Gillett]

I did similar to my Sankyo 301, many years ago, 16.666 for silent 25 for sound.

In my poor student days I shot at 16 or 18 for economy's sake, recording any sound to portable reel to reel or cassette tape, also to save money. At about double the price of silent plus the cost of the camera, sound on film was out of reach.

I later striped some of the films and transferred the taped sound via the Eumig 710D. The Eumig's (unofficial) variable speed control allowed rough syncing of projector to tape.

[Alwyn Adkins]

Back again.

On an 8 series Eumig, by setting the internal adjustor to 60 cycles, you can now slow the speed controller below 18 as there is more traverse, and achieve 16.666 FPS which on the 3 blade shutter will be strobe free.

I did try putting the Hz wire onto the 60Hz pin, but no joy, I still got a bit of flicker with my camcorder at 1/50th of a second.

I have a Eumig 820 Sonomatic but it doesn't seem have a speed controller. Is that an internal setting?

I connected up my variable-volt power supply, set it to 194v and am getting no flickering at all, so if I can't do anything else, this will suffice. It would be nice to not to have to use it though. It does drift slightly, although it's only for 15 minutes at a time; I'm glad I don't have to monitor a 3hr VHS tape as closely as this!

[David Strelitz]

Back again.


I did try putting the Hz wire onto the 60Hz pin, but no joy, I still got a bit of flicker with my camcorder at 1/50th of a second.

I have a Eumig 820 Sonomatic but it doesn't seem have a speed controller. Is that an internal setting?

I connected up my variable-volt power supply, set it to 194v and am getting no flickering at all, so if I can't do anything else, this will suffice. It would be nice to not to have to use it though. It does drift slightly, although it's only for 15 minutes at a time; I'm glad I don't have to monitor a 3hr VHS tape as closely as this!

Unless the 820 is different, I was not referring to moving any wires, but a mechanical adjustor that allows more movement of the metal drive against the drive discs.

[Alwyn Adkins]

Dave, arr, yes, found it. It has almost no resistance when I twist it to "60c/s" from "50Hz" and I can't see any difference to the film speed.

[Alwyn Adkins]

I've just borrowed a mate's projector, an Elmo ST-180, to digitise his cine film, as his projector's sound is much better than my Eumig. Lo and behold, the variable voltage/speed trick doesn't work on the Elmo. The speed stayed rock-steady right down to 150v (240v) and the lamp then started to go dim! Surprised, I was.