8mm Forum: IF BLU RAY TAKES HOLD.

This is topic IF BLU RAY TAKES HOLD. in forum General Yak at 8mm Forum.

To visit this topic, use this URL:
https://8mmforum.film-tech.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=8;t=000853

Posted by Andrew Wilson (Member # 538) on April 29, 2008, 11:05 AM:

Hello fellow members.Just a thought but if blu ray takes hold of the dvd market on both sides of pond,then in theory all off you GS1200 owners should be very happy indeed.Blu ray has its sound tracks recorded at the correct speed...ie 24fps.If that is the case
then you shouldn't need to use the pulse sync feature of that machine.Is this fact or fiction?.Andy.

Posted by Brad Miller (Member # 2) on April 29, 2008, 08:03 PM:

Doesn't matter. Regular DVDs from Hollywood are mastered at 24FPS too, but then again good old fashioned VHS also ran at the correct speed. Sure it wasn't literally 24FPS, but it was converted electronically so that the runtime was the same.

I am not aware of any DVD player being able to be hooked up to a pulse sync though, so the entire issue is moot.

Posted by Jan Bister (Member # 332) on April 30, 2008, 01:03 AM:

Actually, Brad - I'm surprised you're missing this small but important detail - the NTSC standard specifies that video tapes and DVDs play back at a frame rate of precisely 23.976fps. And in countries that use PAL, everything jumps to 25.000fps, a 4% increase in speed (and accordingly a shorter runtime). [Eek!]

Also, DVD players aren't hooked up to the GS1200 - it gets its sync from a separate unit connected to it while the DVD player functions independently from the projector. From what I've heard here on the forum, the problem with the GS1200 pulse-sync units is that they sync the projector to exactly 24fps, not 23.976fps.

Someone correct me if I'm talking complete rubbish here...

Posted by Jean-Marc Toussaint (Member # 270) on April 30, 2008, 01:37 AM:

The purpose of the pulse sync unit is to make the GS1200 run at the correct speed. That and only that.
Pedro has developped one unit that can run at 23.976fps
And those working with professionnal non-linear editing softwares know how to convert 25fps to 24. [Big Grin]

Posted by Graham Sinden (Member # 431) on April 30, 2008, 07:32 AM:

Correct me if Im wrong. But dosent the CORRECT speed depend upon the internal circuitry of the GS1200 like the speed board. If this is out by a fraction then would the sync speed be out or could the sync box override this?

Graham S

Posted by Kevin Faulkner (Member # 6) on April 30, 2008, 07:59 AM:

Forget the speed control board in the GS as this is not the issue here unless its way off speed in normal use.

The std speed controller in the GS is not acurate enough to run a film in sync with a PAL 50 or NTSC 60 source.

What the Crystal sync unit (Pedro's Unit) does is to put out a pulse to the GS for every frame but accurately timed. In other words the GS will move on one frame per pulse from the Crystal sync unit and as the unit is giving exactly 24 or 25 fps you can be assured that is what your getting each and every 1 second.

The built in speed control board may be giving 24.5 fps and this would then add up over time resulting in loss of sync which is why the GS must be controlled from an accurate external source.

With the Crystal sync unit controlling the GS this accurately there is no need to have the DVD, Laserdisc or VHS controlling the GS as the two will stay in step.

It is possible to get or make a unit which can convert the TV Sync pulse from the video signal and use that to control the GS.
This is probably a better route for NTSC origination as Pedro's unit is designed for PAL use (50 cycles or 25FPS)

Hope that helps clarify how this is working.

Kev.

Posted by Osi Osgood (Member # 424) on April 30, 2008, 08:47 AM:

Wow, I am truly impressed! After reading this, I'm not sure I would ever have the technical prowess to re-record anything on my own!

Posted by Graham Sinden (Member # 431) on April 30, 2008, 11:29 AM:

Thanks Kev,

What I meant by my post was with a pulse sync box (pedros) connected I wasnt sure if the internal circuitry still had a bearing on the speed but I can see now how Pedro's box works.

On a different note, my GS1200 has been playing up recently as I fear the motor may be going as sometimes the GS slows down a bit and the speed knob has no effect. I did throughly clean the switches (didnt work) but I still have to check those diodes as said previously in another post (excellent search function on this forum). The main motor does get very hot.

Anyway my question to you is on a faulty GS as above, would using Pedro's box still give me 24/25 fps and force the GS to run at that speed, or would the fault not allow to do it? Interesting to see if it can perform miracles.

Graham S

Posted by Jan Bister (Member # 332) on April 30, 2008, 03:03 PM:

Graham,

as Kevin said, the GS1200 will make its best effort to "stay in step" with an external sync pulse (Pedro's box)... but if the motor is running very hot and slows down it probably will do that whether or not you sync your GS1200 externally. Sounds to me like the motor needs replaced, otherwise it's simply a case of the control board saying "Come on! Run!!!" and the motor moaning "I can't! Sorry!" [Big Grin]

Posted by John Clancy (Member # 49) on May 01, 2008, 03:40 AM:

On the other hand it may be the speed control board playing up. Connecting a sync' pulse may bypass the problem. Could be worth a try.

Posted by Kevin Faulkner (Member # 6) on May 01, 2008, 04:37 AM:

No, if the motor is getting hot its either failing or there is another problem.

I had this very same issue with a GS last year. Running very hot, slow and with no speed control. I tried putting the motor in my own machine at which point the motor ran ok at the right speed and cool.
I then tried the speed control board in my machine and again all was well.
So what was the cure? Well 2 things compounded the problem.
1, There was no play in the top Cog train so the cogs were running very tight. There must be play between all the cogs and the worm drive.
2, Someone had used a black grease which had gone hard on the cogs and the worm drive and its bearings.

This particular machine had obviously been stripped down earlier in it's life to have a 2 blade shutter installed. And I think the person doing the conversion used the wrong grease and reassembled the machine without paying attention to the cogs issue. Incidentally the 2 blade shutter was cut out of what looked an old tin can complete with printing!

I stripped the machine and cleaned all the hard grease off the cogs etc and then re-greased and assembled the machine with play between the cogs and it immediately ran smoothly, at the right speed and cool and has been doing so ever since.

If your motor is running hot because of other problems then get it sorted and don't run it like this as it will burn out the windings.
To check the motor. Remove the drive belt and then run it. If you can now adjust the speed etc and it runs cool then investigate the internals of the machine as it is unlikely to be the motor.

If the speed of the motor is way out then Pedro's box will not be able to pull the speed in either.

Kev.

Posted by Graham Sinden (Member # 431) on May 01, 2008, 07:38 AM:

Thanks Kev, I will try that ASAP.

The problem is a bit intermittent as it comes and goes. The projector slows a bit although never seems like it would stop. When it slows, the speed knob (usually in center position) can go down but wont speed up when turned in the other direction. This seemed weird to me.

I throughly cleaned the speed switches (on the end) with switch cleaner. This worked for a short while but then the problem came back. Took the back off and the motor was too hot to touch. Read here that it could be the diodes but havent checked them yet.

Kev, 2nd half of this post should really be in 8mm section. Move it if you want.

Graham S

Posted by Kevin Faulkner (Member # 6) on May 01, 2008, 08:00 AM:

Graham, It's not possible to split the thread. So it will have to remain here.

Posted by Brad Miller (Member # 2) on May 03, 2008, 02:02 PM:

Again, even with a sync motor running on the GS it is a moot point because 23.976 vs. 24 really doesn't matter once you hit a reel change and find out that your print has extra frames not in the video version or the video version has extra frames not in the 8mm print. The fact of the matter is you have to get the GS running perfectly in sync with the DVD/video on a practice run, then back it up and let it go until you hit a reel change and lose sync.

I have done many re-recordings without the sync motor too. All you have to do is a practice run tweeking the variable speed to stay in perfect sync and setup your projected image side by side of your tv monitor. The trick is to blur your vision and watch in between the two images. Watch for sync at the camera changes, NOT the actor's lips. If you see one flash ever so slightly before the other, you know which way to barely tap the speed control so that you never are off more than 1/2 frame in either direction. That is unnoticeable.

UBB.classic^TM 6.3.1.2