8mm Forum: Slow ST-1200HD MO

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Posted by Vidar Olavesen (Member # 3354) on July 27, 2013, 10:43 AM:

I just got a new (old really) ST-1200HD MO and it seems to run at about 20 fps or so. Much too slow and it's apparant in the sound, so I guess it's around that framerate. Is there anything I can check or adjust?

Thanks

Posted by Steve Klare (Member # 12) on July 27, 2013, 10:57 AM:

Try running it with the lamp lit a couple of minutes and see what happens. This is pretty common with these machines.

If I start mine from dead cold it's slow too.

Posted by Claus Harding (Member # 702) on July 27, 2013, 02:50 PM:

I have always made a habit of running my 1200 (no lamp) for about four to five minutes before screening anything. This gets the flywheel up to speed and stabilizes the projector for sound use.

Claus.

Posted by Vidar Olavesen (Member # 3354) on July 27, 2013, 03:09 PM:

Asked my son to try it out, waiting for response now. So if it's the same as yours, is it fixable? My two other ST-1200's are not like this.

Thanks for the responses

Posted by Andrew Woodcock (Member # 3260) on July 27, 2013, 06:41 PM:

The problem with all projectors that use a ac motor for the main drive section as opposed to a dc motor, is that they rely on some kind of mechanical switching process and usually clutch arrangement to adjust from 24fps to 18fps. As a result they all have intermediate rubber wheels driving the main shaft. The rubber on steel (or rubber) as is evident in the ST 1200 series (as well as many others) has this mechanical rubber tyre arrangement via a sprung clutch to the shutter wheel and main drive shaft. The problem with this arrangement is it relies on good friction and constant spring pressure. Rubber tyres, springs and mechanical clutches all wear in time resulting in slippage and therefore a slower drive speed than intended. Unless the owner is prepared to constantly maintain all of these items to get them back to original specification, I am afraid we all have to accept the end result of many hours of use and deterioration to these parts and settle for less than perfect. Any machine using an electronically governed dc drive mechanism for the main drive on the projector ie Elmo GS1200 or Bauer T610, 510 etc etc, doesn't witness these problems as they are more or less directly driven apart from a main drive belt which generally doesn't suffer from lack of friction until it snaps apart from if lubrication comes into contact with it and associated pulleys.

Posted by Tom Photiou (Member # 130) on July 28, 2013, 03:15 AM:

It sounds like it may just need a good clean up in the drive system and refresh lube, has it been sat around for a while?

Posted by Vidar Olavesen (Member # 3354) on July 28, 2013, 04:13 AM:

I believe it's been at a stand still for a while, yes. But it's not uneven slow, it's a constant 20 or so frames I think. I will open it next time my son comes around and see if anything is looking in need of oil

Posted by Andrew Woodcock (Member # 3260) on July 28, 2013, 06:07 AM:

What could you possibly oil to make the machine go faster? I would be inclined to check for wear on the rubber wheels and that the springs are pulling the clutch to the shutter firmly in both speed settings first. These machines have a relatively powerful motor for what they are driving and unless the rotor has overheated severely or the stator windings were more or less burned out, the speed of these type of motors will be at synchronous design speed. Usually just by applying pressure to the speed controlling lever you will see a difference in the speed as more or less friction is applied to the shutter wheel from the clutch and drive chain.

Posted by Vidar Olavesen (Member # 3354) on July 28, 2013, 06:32 AM:

Will test that too, thanks

I am thinking things that go round and not been used for a while, often need oil. As my Chinon was doing the same, going slower and slower. Opened up the arms and oiled it, runs smooth now.

Posted by Andrew Woodcock (Member # 3260) on July 28, 2013, 10:10 AM:

on these machines very little, if anything requires oiling, just use Alvania grease to lube metal rotating non friction parts and silicon grease for nylon gears.

Posted by John Capazzo (Member # 157) on July 28, 2013, 10:51 AM:

Vidar,

With the rear cover off, plug it it and turn it on. You don't need film at this point since you should still hear it running slowly. Lift the clutch/speed wheel assembly lever away from the shutter and bring it back down again. Try that several times; then try it with film (with the cover on). Keep it running and it should pick up. A worn out wheel isn't the cause of it running slowly. Loud, yes.

It's definitely not the motor. Those motors are built to last indefinitely. The only other problem could be a capacitor (which is essentially the start up device) and is simple to remove and install.

Hope this helps. Let us know.

Posted by Vidar Olavesen (Member # 3354) on July 28, 2013, 11:39 AM:

Will test your suggestions on Wednesday when my son comes again with the projector

Thanks for all the suggestions, have stuff to try out now :-)

Posted by Andrew Woodcock (Member # 3260) on July 28, 2013, 03:03 PM:

Johns advice is spot on but also test the spring pressure and clutch assy is correctly positioned as on some of these the whole clutch pivots on a stationary piece of the structure and can sometimes become dislodged and therefore out of postion. This is a feature found on the later D's & HD's done as a mod by Elmo to try to improve the drive chain mechanism. If anyone has previously removed the clutch then it is very likely to be put back out of position and therefore not work correctly. On the original standard ST's they had a simpler version of this mechanism and often were not even fitted a spring to pull the clutch onto the shutter despite the fact that the lugs were there to fit one if needed.

Posted by John Capazzo (Member # 157) on July 29, 2013, 08:15 PM:

Andrew, yes. The spring could lose it's tension also. The other slight problem is removing the clutch assembly. It's relatively simple to remove (only two screws) but I didn't want to suggest to Vidar attempting this since putting it back is trickier. Anyone who is unfamiliar with how it goes back will have a hard time adjusting the safety shutter. If it's not re installed perfectly, the image will be dim. The safety shutter won't spring back up entirely. I've learnt how do do it after an hour of playing around with it.

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