Elmo ST Running Very Slowly

[Rich Malmsten]

My Elmo ST1200 is running very slowly, at only about 60% normal speed. It's very apparent from the sound being quite off. I determined how slow it is going this by comparing how long it takes for a reel on the front arm to rotate 10 times verses the time on another well-running projector.

I replaced the two drive belts, and that had no effect. It still runs very slow.

Toggling the 18 / 24 fps switch on the back, or holding it up so it's firmly engaged, has no effect on the speed, either.

Does anyone have any idea what the cause is?

I had another ST1200 several years ago that had the very same problem. I ended up buying this one as a replacement. ST1200s are nice projectors, and if possible, I'd like to repair them.

[Steve Klare]

Hi Rich,

Something that I saw on my own was that the motor pulley was worn and it's effective diameter became less and less, this meant the belt moved fewer centimeters per pulley rotation and the machine naturally ran slower. (-like it was stuck in first gear!)

-an aggravating factor here was the belt slipped for a couple of seconds on cold-startup and wore the pulley sheave as a result. By the time I saw this, the belt was actually visible when looking at the pulley hub.

Part of the process of fixing this (other than a new pulley) was properly lubing the machine, particularly the worm. This ended the belt slippage and hopefully will preserve the new pulley.

There's an entry in the Index of Technical Topics under "Projectors - Super 8mm" titled "Lubricating Projectors".

[Rob Young]

Another thing to look for is the rubber around the circular shutter hasn't gone soft and gooey, although I think Elmo only introduced this rubber on later HD versions, so it maybe that Rich's ST1200 doesn't have this.

If it goes off, which is common, it causes the rubber to stick to the rubber drive wheel and slow the projector down sometimes to a grinding halt.

The fact Rich's projector seems to be running a slow but constant speed makes me think it isn't this, but worth checking none the less.

If it is this, the rubber can be removed although no mean feat and there are topics discussing this.