This is topic Eumig Mark S 802: drive discs & bulb in forum 8mm Forum at 8mm Forum.
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Posted by Richard Gordon (Member # 1838) on December 05, 2009, 10:47 PM:
I've just acquired a Eumig Mark S 802 and would welcome your comments on the following problems:
1. The 2 rubber-covered drive discs are well-used. This probably explains the slowing down and stalling of the film drive that occurs after a few minutes of running the projector at 24fps in reverse or rewind. It's then also not possible to run the projector forwards for a while. I've seen the following recommendations posted on this forum: a. Clean the steel ball drive and the rubber discs with alcohol or brake cleaner. b. Sand the rubber discs with very fine emery cloth. I'd like to know if coating the tracks on the discs with superglue (and letting it dry completely!) would give a long-lasting friction surface without damaging the rubber?
2. The projector is fitted with a 75w 12v lamp which produces a much dimmer picture compared with my Eumig Mark DL or my P8 both of which have 100w 12v lamps. Is it OK to fit a 100w 12v lamp to the Mark S 802?
Regards, Richard Gordon
Posted by Alexander Lechner (Member # 1548) on December 06, 2009, 06:49 AM:
I had the same problem with a slipping disc; when looking at it closely you will see that the tracks (18 and 24 fps) that the ball drive runs on is completely smooth and not "rubbery" anymore. I treated it with very smooth sand paper until the whole disc was in the same state all over and you could also feel a difference in the surface when you touched it with the finger: it was not "slippy" anymore but had some grip. The projector works without problem now.
I would not use super glue as it does not produce a rubbery surface when it hardens but a "glassy" hardness.
I got a 807, which - according to the instructions - also requires a 75 W bulb, and it had a 100 W bulb in it when I bought it, so it was operated with it in the past; there is nothing wrong with the projector so it might be possible to use the stronger bulb without harming the equipment.
Posted by Richard Gordon (Member # 1838) on December 06, 2009, 04:42 PM:
Thanks Alex for your reply.
I'll clean and sand the discs and give the superglue a miss!
About using a 100w lamp in place of the official 75w: after I posted the question I found a relevant thread on this forum which concluded that 100w might strain the transformer and that the fan might not cope with the additional heat. I've now compared the lamp housings and cooling arangements of the mark S 802 (75w enclosed) with the mark DL (100w separate lamp/reflector, open housing and trunking direct to fan) and decided that using a 100w lamp and integral reflector in the 802's relatively enclosed 75w lamp housing will cause excessive heat build up. So I'll leave well alone and stay with a 75w lamp. Regards, Richard
Posted by Michael Dixon (Member # 1836) on December 06, 2009, 06:52 PM:
Without claiming any special knowledge of that particular projector or the transformer, upping the lamp to 100 watts is obviously a 25% load increase on the transformer. A 75 watt lamp is 6.25 amperes at 12V, 100 watts is 8.33 amperes. Not only does the higher wattage lamp increase the heat load, but so does the increased load on the transformer. A rule of thumb for motors and transformers is that each 10deg C increase in temperature shortens operating life by 50%. Belts will be affected also.
Posted by Winbert Hutahaean (Member # 58) on December 06, 2009, 10:16 PM:
But according to super8data, there is a Eumig 802 with 100w 12 v bulb type:
So what do you think?
Posted by Alexander Lechner (Member # 1548) on December 07, 2009, 03:42 PM:
I think it is just stated wrongly at super8data; it was the same way on super8wiki until I changed it and since then nobody has been touching it. I think the problem is that some information is just copied from one 8 series projector to the next one as they are very similar.
Posted by Winbert Hutahaean (Member # 58) on December 07, 2009, 03:48 PM:
But I do remember one of Eumig (I forgot which one is that, can be 807 or 802) appeared on Ebay where one was stated exactly on the machine as 75w/12 v but another Ebay seller had a machine with 100w/12v spec written on his machine.
So I think there were 2 version of Eumig regarding the power of the bulb.
Posted by Michael Dixon (Member # 1836) on December 07, 2009, 07:55 PM:
Apparently Bolex in Switzerland now has all the rights to the Eumig brand. Might inquire of them regarding needed parts.
Posted by Josef Grassmann (Member # 378) on December 08, 2009, 07:17 AM:
Eumig did convert some of there Eumigīs 802 807 and I believe 810 fron a certain serial No. onwards from 75 watt bulb to 100W.
The 75 Watt version is very rare in Germany. Therefore I didnīt know it in the past.
When Eumig changed from 75W to 100W they also changed the transformer, thatīs for sure!
If you need detail information I have to search through my Eumig files.
Posted by Richard Gordon (Member # 1838) on December 09, 2009, 08:20 PM:
Hi - here are my replies to the points raised:
1. Changing the lamp from 75w to 100w is actually a 33% increase not 25%. I suspect that there will be little extra heat generated in the copper wire of the transformer by the increased current but there will be a third more heat from the lamp. The projector fan might have difficulty keeping the lamp area cool enough.
2. I think Eumig upgraded the mark S 802 at some point to a 100w bulb. The super8data site describes the projector as having a 100w lamp with a total power consumption of 175w. The model identification plate on my projector specifies 75w lamp and total power consumption of 145w; the difference of 30w being the lamp and, I guess, a more-powerful motor to increase the fan-cooling. Regards, Richard
Posted by John Capazzo (Member # 157) on December 10, 2009, 07:56 AM:
Hello Richard, in regards to the slowing down problem of your Eumig, do NOT sand the rubber discs. You don't want to remove anymore rubber than what you have. The ball wouldn't be able to reach the discs if you remove even the slightest bit. In fact, you'd like to add more rubber if you could. The misconception is that the rubber discs are what slows down the machine when it's a small spring that loses tension from not being run enough. The spring can be replaced, but it will take roughly 6 hours to do. (3 removing in and 3 replacing everything).Alot of work and it's tedious. Not worth it. I have a fne running Mark S 810 with sharp 1.2 lens, but you're in UK amd shipping would be astronomical.
Posted by Richard Gordon (Member # 1838) on December 10, 2009, 05:24 PM:
Hi John, thanks for your advice. All I've done, since my original post, is to use cotton earbuds soaked in propanol to clean the drive ball and the forward and reverse rubber discs. The projector is now running reliably (so far!). Regarding the sensitivity of the drive to the thickness of the discs, it's not clear to me whether it's the thickness or smoothness of the rubber that's the controlling factor. This projector has developed indented tracks along the 50c/s 18 and 24fps positions. If I switch the ball to the 60c/s positions, which don't have indents, the projector runs more reliably. This could support both the thickness and the smoothness theories. On the other hand, other threads on this forum have reported success with sanding with very fine emery paper; simply to provide a surface with a better grip. What's your view on my "superglue" suggestion? It would increase the thickness! Regards, Richard
[ December 11, 2009, 03:31 AM: Message edited by: Richard Gordon ]
Posted by John Capazzo (Member # 157) on December 11, 2009, 03:26 PM:
Hi Richard, the thickness is of the rubber controls the speed to a point but the main reason why it begins running slowly is because of not being run enough. People put away projectors for 20 years and that's the worst thing for a machine. There is a spring that loses it's tension located towards the right of the machine (behind the control knobs when you remove the control knob plate) from not being run enough. It can be replaced (from the back ONLY), but it takes hours. It's not worth it (especilayy if it's not a dual 8 sound). I'll give you an example of the rubber discs NOT being the problem: I had two Eumig machines; one was an 802 the other an 807 and the rubber discs were mint in box. The machines were hardly run; and it still played slowly. It obviously couldn't have been the discs, and the wattage was correct, so the only other problem was the spring (no belts in those machines). I'll send you a pic of what I'm referring. As far as adding rubber: it won't work. You'd have to get thin gauge rubber and the adhesive you apply may be too thick. It may be uneven and then the sound will be worse. The only way would be to remove the old rubber and that will be tedious. Remember: if you remove any rubber with sandpaper or emery will make it flat, yes, but the ball won't reach the discs. Hope this helps.--John
Posted by Richard Gordon (Member # 1838) on December 12, 2009, 09:37 PM:
Hi John, the rotational speed of the disc is basically controlled by the position of the ball on the disc - the further from the centre the slower will be the disc's rotation. However, if there is insufficient friction between the ball and the rubber, the ball might slip and the disc will rotate too slowly or not at all. Appropriate friction can be ensured by a combination of pressure of the ball on the rubber and the roughness of the rubber. So I'm not yet convinced that roughening the surface is wrong. I also don't understand the concept of an unused spring losing its tension; I'd have thought that a lot of use would have that effect. Regards, Richard
Posted by John Capazzo (Member # 157) on January 26, 2010, 03:49 PM:
Haven't been on the site for over a month. How did you make out with the Eumig running slowly? I hope all is well with it.--John
Posted by frank arnstein (Member # 330) on January 28, 2010, 04:50 AM:
Hi to the members on this thread about Eumig speed loss.
What can make these run slow is incorrect adjustment of the outer motor pivot mounting.
The outer mount is an eccentric one & designed to adjust the drive ball position correctly on the disc. If its slightly out, the ball can't drive the disc efficiently. It must be located exactly in line with an imaginary vertical centre line of the currently driven disc.
When that line is located, the disc will drive easily in both directions.
Make sure the claw cam groove is lubed as well as the shutter shaft bushes.
Roughening the rubber disc surfaces with fine emery cloth is Ok, as its important to restore the rough grippy rubber surface & remove grooves in the surface. Removing a tiny amount of rubber will not have any negative effect on the pressure between it and the ball as the pressure spring will take up any slack.
Do not apply Superglue to the disc surface or it will be ruined.
Adjustment of this outer side pivot mount is done while the unit is running with film in it, to provide a load on the machine.
Loosen the 2 pivot mount screws & push the pivot up or down a tiny bit & see the effect on speed. It is on slotted holes so it will move up or down or sideways.
See if it improves the drive speed & then check that its even drive for both forward and reverse. You may need to move it sideways to get it to finally drive both directions properly.
Ensure the sliding speed fork doesn't pop out of its slot. That will happen if you move the mounting downwards too far.
Let us know if this fixes your problem. It should do the trick if done properly and carefully.
As for the Eumig S 802 lamps, here in Australia nearly all are 100w Halogen. Most S 807 have only 75w but not all. Some do have 100w. They have a specs plate on the back cover which confirms wether it needs a 75w or a 100w. Best to go by that.
[ January 28, 2010, 07:41 AM: Message edited by: frank arnstein ]
Posted by Martin Jones (Member # 1163) on January 28, 2010, 06:14 AM:
Frank is right in that the motor shaft must be exactly in line with the line halfway between the discs for the drive to work properly. But it's the side to side adjustment that determines this; the up and down adjustment controls the location of the ball in the speed change lever fork. What he doesn't say is that this is essential for BOTH Forward and Reverse to work properly; if the ball IS correctly placed and one or other of those direction is problematical then it's not the ball alignment that is needed... it's attention to the stops and spring located behind the main control knob on the front of the machine. These determine how far the motor/ball assembly can tilt each way (the stops)and how much pressure (the spring) the ball exerts on the disc. And as said previously in this thread... it's a PIG!
It's probably also true to say that if the parts are all original and the paint sealing those screws on the rear pivot mount is unbroken the ball will still be in the original factory position...i.e. correctly placed.
Also, adjustment of that eccentric pivot mount has another (often overlooked) function.... making sure that the fan, which is located in the casting below the motor, does not foul on the casting. The clearances are very small; if the fan is not located exactly right on the motor shaft (it's a sliding fit and held in position only by a spring) it will bind, with obvious consequences.
Posted by frank arnstein (Member # 330) on January 28, 2010, 07:03 AM:
Thanks for the response but I don't think you have grasped fully what I tried to explain about setting the eccentric motor pivot.
I was not talking about a centre line between the 2 discs at all, although that is also an important line to aim for when setting the forward & reverse to be equal.
I was talking about another important line.
By moving the eccentric mounting up & down, it also moves the ball back & forth on the disc that is being currently driven. As long as the speed fork remains in its slot, it will still do its job of sliding the ball along the surface of the disc, varying the output speed. The thing to realise, is that when you lift the mount up, the ball will also move away from, or toward, a vertical line on the driven disc at its widest diametre. This center line is where the ball will spin the disc most easily in either direction because there is no side forces to make the ball skid. The ball will roll cleanly instead of rolling and also skidding. A skidding ball won't drive properly due to friction slowing it down.
Do not confuse this line with a central point between the 2 discs.
I also did say to ensure it works well in both directions, have another read.
"It's probably also true to say that if the parts are all original and the paint sealing those screws on the rear pivot mount is unbroken the ball will still be in the original factory position...i.e. correctly placed."
I don't think this is neccessarily so, after much use and time.
When I encounter this problem, I adjust the pivot mount & break the factory paint seals. They drive Ok after correct resetting.
"Also, adjustment of that eccentric pivot mount has another (often overlooked) function.... making sure that the fan, which is located in the casting below the motor, does not foul on the casting. The clearances are very small; if the fan is not located exactly right on the motor shaft.
I don't believe the eccentric adjustment is to provide this fan clearance, as if you were to move the drive ball away from the sweet spot on the vertical central line, the drive from the ball to the disc would be upset & speed loss will result immediately.
Posted by Martin Jones (Member # 1163) on January 28, 2010, 08:54 AM:
There is only one correct alignment point, the point at which all the parts (ball,discs,motor shaft speed fork) are in the correct relative positions, and that point is established at the factory by means of the adjustments provided. And that point is achieved with new,"perfect" components. Wear on those components will cause the interaction between those parts to gradually become ineffective, but the alignment between those parts will always be the same as long as the alignment adjustments are not interfered with.
As the parts wear, the mechanism is substantially self adjusting; it is only required to ensure that it provides sufficient pressure between ball and discs to provide reliable drive. Your "sweet spot"/ "sweet line" remains exactly where it was set, unless the pivots (shaft or bushes or both) become worn.That is easy to check; if they have no play, the original "undisturbed" adjustment holds good. If they are replaced because of wear then the adjustment needs re-doing.
There are a number of factors that can affect that drive reliability, ignoring friction elsewhere in the machine....
1. The condition of the disc rubber, both in terms of surface shine and thickness. That has been dealt with many times.
2. The surface of the ball. As that is highly polished "as new" becoming "more polished" should have little effect.
3. The interaction between those two components, governed by whether the ball can physically move into contact with the disc and whether there is sufficient, but not too much, pressure at the point of contact between the parts to duplicate the original conditions.
As said earlier, the self-adjustment which compensates for dimensional wear of both ball and disc rubber is already built into the machine, provided by the spring that enables the motor to tilt further until the pressure is sufficient to provide the drive, but only if the stops are correctly set to allow it.
Interestingly, Frank, I can't recall a post where you have commented on the function of these components. If you have, perhaps you could point me to it?
What I do know is that I have recently been involved with the conversion of a S710 (same mechanism) for telecine purposes, and faced with the same drive problems where both the disc rubbers and the ball were in virtually "as new" condition and having tried all the usual suggestions (including your "eccentric mount" adjustment) I finally solved the problem by replacing the "motor tilting spring" with one from my stock of new tension coil springs, selected for the correct tension for the job.
And yes, I did miss your reference to "both directions".. remiss of me.
[ January 28, 2010, 10:25 AM: Message edited by: Martin Jones ]
Posted by Mike Carro (Member # 933) on July 24, 2010, 11:58 AM:
I also have a Mark S 802 with the same slowing down problem and won't work in reverse. Never having one of these machines before I was surprised at the mechanism. With the back off and the machine running I put some pressure with my finger on the motor and instantly the reverse starting working. I tried the same thing in forward and it too sped up a bit. So it must be a combination of pressure and the grip of the disc. I don't know if it's worth fixing.
Posted by Gary Crawford (Member # 67) on July 26, 2010, 10:37 AM:
Yes...part of the problem could be lack of pressure, and alignment, ...but on my old eumigs...the rubber wheel got worn down to the point where you couldn't put enough pressure on it to make it not slip. The metal ball hitting that same spot on the disc...over and over...years and years. Therer was a slick slight depression on that part of the disc. For a while, I put belt dressing..non slip belt dressing on the wheel...which kept it going for a year or so more before it finally would not run at speed anymore.
Posted by Tony Stucchio (Member # 519) on July 26, 2010, 07:50 PM:
These models of Eumigs, with the rubber disc drives, were great machines in the '70s, but unlike belt driven systems, once they wear down they are essentially dead for viewing sound films. (You won't notice the speed issue on silents.) Phil Johnson was selling replacement discs for a while, but they were something like $250. You can get a full projector in great condition on eBay for less -- which is your best bet if you really love Eumigs. But trying to revive one is time consuming, frustrating, and darn near impossible. You will get it to run fine for maybe a few films (which is what happened to me), maybe a week, or maybe a year (as Gary said), but after that, fuggettaboutit!
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