8mm Forum: What this pulley is for (ST-1200)?

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Posted by Winbert Hutahaean (Member # 58) on January 02, 2008, 11:49 PM:

Hi guys,

I have a big problem last night when using my ST-1200.

Suddenly the motor stopped and when I opened the case, I saw there were two pulleys sitting side by side, One belt snapped from the right pulley as picture below:

The motor stopped becuase the remain of broken belt was trapeed inside the rotor. I pulled out the ermain and turned on the projector.

Amazingly, the projector run again. But I believed there was an important role taken by this second pulley, so I turn off the projector again.

1. So can you guys tell me what is the main purpose of the second pulley, why the projector could run without being belted?

2. Secondly, though the projector run, but it was too noisy, sounded that the rotor touching a metal or somekind like that. Do you think if I installed a repalcement belt the noise would also go?

3. Can you also tell me where is the place to do speed adjustment (on Sankyo 800 I could see two small buttons representing 18 and 24 fps, but I didn't see inside the ST1200)

please help me guys,

Posted by Kevin Faulkner (Member # 6) on January 03, 2008, 07:48 AM:

Winbert, The ST1200 series doesnt have any fine speed adjustment as it is being run by an AC motor. Being a synchrous AC motor it maintains it speed by using the mains frequency (50 or 60Hz). The pulleys are used to change the machine from 50 to 60Hz operation. I thought there was a picture inside the rear cover showing the pulley belt positions?

I'm surprised that the machine is still running with that belt broken as from memory the ST needs that belt to drive the two pulleys with the motor drive going to only one of the pulleys. Maybe the machine wont run now in the 18fps position.

Its a while since I have worked on the inside of an ST1200 maybe someone can do a physical check for you.

Kev.

Posted by Joerg Niggemann (Member # 611) on January 03, 2008, 09:58 AM:

Hi,

the main belt inside the ST drives both pulleys for 18 and 24 fps. Therefore the projector can run without the second belt at both speeds, but maybe not that stable...? I know some Bolex machines where 2 belts run in parallel, too.

At the moment I have no ST, but here you can see some photos. Take a look at "foto13".

Joerg

Posted by Jim Schrader (Member # 9) on January 03, 2008, 10:57 AM:

Joerg I see you have that plate on the shutter I was wondering what this is for is it for adjusting it and can one get that site in english? thanks Jim

Posted by Joerg Niggemann (Member # 611) on January 03, 2008, 11:15 AM:

Jim, I'd also like to have that site in english because I don't understand a word of the italian text [Confused]

. I found it when searching for st1200 photos to clarify Winberts belt question. I remember there was a discussion in this forum about that shutter plate, but don't ask me...

Joerg

Posted by Kevin Faulkner (Member # 6) on January 03, 2008, 12:04 PM:

Yes I stand corrected on my reply above. I was trying to answer from memory.

I too would like to know what that adjustable shutter was for?

Kev.

Posted by Jan Bister (Member # 332) on January 04, 2008, 04:40 PM:

Hmm, I have two guesses....

1. the additional shutter plate is for heat protection, that is, to absorb as much heat from the lamp as possible and prevent the shutter belt from warming up too much and possibly melting over time...

2. as the adjustment range is very small, my other guess is it's meant for fine-adjusting the timing of the claw pull-down and "lights out" phase so the film frame isn't still moving when the "lights go on again" which would result in a slight wipe effect on the screen...

Posted by Jan Bister (Member # 332) on January 04, 2008, 09:38 PM:

By the way, the English translation:

Click me!

Posted by Kevin Faulkner (Member # 6) on January 05, 2008, 05:25 AM:

Jan, I agree with you about the claw timing etc but this is an adjustment you would do at the point of assembling the shutter blade onto the main shaft.
The other point is why didn't they put that as std on all the 1200 series machines. I think there is more to it than that but cant quite put my finger on the reason.
It's not even shown in the service manual as either a part or an adjustment.....bizarre!

Kev.

Posted by Jim Schrader (Member # 9) on January 05, 2008, 08:40 AM:

I could not get your page to work Jan but went to google and retranslated it for myself the intructions are for replacing the rubber seal on the shutter,and there was still some words that google did not translate, but another question comes to mind why take that off it looks like it is recessed from the outer part where the rubber shutter is just wondering?

Posted by Joerg Niggemann (Member # 611) on January 05, 2008, 09:40 AM:

In "foto 11" on that page you can see that the plate was adjusted for a longer dark phase before disassembling. It must be some kind of fine adjustment to avoid ghosting effects.

Joerg

Posted by Kevin Faulkner (Member # 6) on January 05, 2008, 10:12 AM:

But once again the question I ask is why is it not on all the ST1200's? and why no mention in the service manual?

That translation worked for me except I dont see any pictures just samll square blocks.

Kev.

Posted by Jan Bister (Member # 332) on January 05, 2008, 07:44 PM:

Hmm, the Italian page seemed to suggest (and I hope I'm not just dreaming this right now) that yes, the light/dark phase is determined by how the shutter wheel is mounted back in place, but IF a fine adjustment is necessary after that then the secondary blades can be moved to achieve this.
Wouldn't really be too surprised to see this missing from the service manual, if Elmo made this change at some later point and forgot to update the manual along with it. Who knows [Confused]

Posted by Joerg Niggemann (Member # 611) on January 06, 2008, 04:37 AM:

Good explanation Jan. This is likely because you can do the adjustment in both directions to compensate a wrong timing. But does it mean that they could not do the timing adjustment 100% correctly during production and had to "correct" it later in a second step? Still strange because of a more complicated production process. I don't know any other model or brand with a "feature" like that.

Joerg

Posted by Kevin Faulkner (Member # 6) on January 06, 2008, 06:06 AM:

This could be the case then Jan. One thing I forgot to ask earlier is what model of ST1200 is this Winbert?

Kev.

Posted by Winbert Hutahaean (Member # 58) on January 06, 2008, 09:43 PM:

Kev,

Mine is M & O model (if that what you are looking for).

Now, with limited resources here in Indonesia, I did what I could do to fix my projector.

I took the power glue (hard glue) and re-joined the broken belt. After leaving it to dry-up for 1 night, I put it back to the pulley....and voila!....it's running again.

And the noise used to come with one pulley belted was also gone. So, it was indeed with one belt the motor could run but they worked so hard and that's why the noise came.

Now my question, I have 2 identical ST-1200s, when I opened the second one to see what was inside the projector, I found that it has square belt while my broken one is round one.

So, can you guys tell me the different function or whatever it was, why the shape of the belt is different?

cheers,

Posted by Steve Klare (Member # 12) on January 06, 2008, 10:06 PM:

Winbert,

This E-bay seller has excellent replacement belts and ships worldwide.

(...and no, I am not him!)

http://search.ebay.com/_W0QQsassZisellprojectorbelts

Your round profile belt is probably a replacement belt that fit the projector, but the square one is most likely the exact part.

Posted by Kevin Faulkner (Member # 6) on January 08, 2008, 04:24 PM:

Winbert, They are normally square section belts on these machines and it would be best if possible to fit the same as the originals.

Kev.

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