8mm Forum: Pedro's sync. box and not constant speed: the final reason of the defect...

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Posted by Ugo Grassi (Member # 139) on June 04, 2008, 09:36 AM:

All of us know the sync. box made by Wolfgang Thuille (Pedro) for the ESS circuit needs, with some GS1200, to be connected to an external transformer to avoid unstediness to the pin control (that one on the rear side), and then to the speed machine.
The instructions explain the defect comes from an exaust capacitor (C401, 47 nF in the ealier machines, 470 nF in the latest), so the suggest is to change that capacitor.
Well, often this is not enough. Now I know the final reason of the defect. The exaust part is a Zener diode. The code in the diagram is ZD402, and it's a 1/4 watt, 6.8 volt.
Change it and everything will work at the best.
bye

Posted by John Clancy (Member # 49) on June 05, 2008, 01:14 AM:

Ugo, you've earned your stripes with this one!

Is the diode change a simple process? For us idiots, is there a photograph or diagram to point us to the offending item?

Posted by Kevin Faulkner (Member # 6) on June 05, 2008, 03:28 AM:

Yes it's 3 cheers to Ugo again. [Big Grin]

I do have a question for other GS owners with the Pedro Box.

If I plug my Sync unit into the GS it does not control the GS straight away. I have to give it a few mins then it will start to work. Erratically at first then it settles down and carries on fine until the next session. It suggests a Capacitor which is slow charging when the unit hasn't been used for a while. I do know that it inst in Pedro's box but is the GS as I have tried it on a couple of std GS's

I think I have heard of this before and only on the Xenons but what is the cause? In all other respects it works fine.
Maybe it's time to get the Scope out!

Has anyone else come across the strange behavior?

Kev.

Posted by Ugo Grassi (Member # 139) on June 13, 2008, 03:45 AM:

http://img143.imageshack.us/my.php?image=pict0117nm2.jpg

look rear the trimmer. There is a free space because I got the photo after the stripping of the diode.

Posted by Mark Norton (Member # 165) on June 23, 2008, 04:44 AM:

Excellent information, many thanks Ugo. Possibly starting to go on mine as well , can't get the needle in the ESS level meter to stay still until the projector has been running for a good few minutes. Does anyone know the best place to get the replacements?

Posted by Kevin Faulkner (Member # 6) on June 24, 2008, 05:31 AM:

Hi Mark, Maplin Part number: QH10L which is a BZX79C 6V8 Zener Diode.

Kev.

Posted by Brian Hendel (Member # 61) on June 24, 2008, 12:42 PM:

I must admit the whole sync pulse things is way beyond me. Can someone post a simple explanation of what equipment is needed to synch up DVD sound with super 8 playback on a GS1200. I am intrigued by the concept and would like to give it a try if it's not too complicated.

Posted by Mark Norton (Member # 165) on June 24, 2008, 02:12 PM:

Brian, you just need one of Pedro's sync boxes which plugs in to the ESS socket. Then the GS runs at exactly the same speed as PAL Video/ DVD etc. I think the newer boxes sync with NSTC. Then it's trial and error to find your start point, then the Projector and video source run in sync, it's easy to re-record films and it's made a big improvement to my collection, many films that had so so sound now have near DVD quality.

Posted by Brian Hendel (Member # 61) on June 24, 2008, 02:33 PM:

So how do you go about ordering one of the sync boxes? Yes, I would need NTSC... So does it match up to the image cuts in the film? I still don't understand how it keeps to the same time. It sounds like it would be a big help in re-recording soundtracks which right now is a major headache.

Posted by Alan Rik (Member # 73) on June 24, 2008, 04:01 PM:

Hey Brian,
Heres the simple:
If you were to record using your GS1200 you would place the machine in record mode and then put it on pause.
Then the DVD would be at the start of where you want it...same frame as the film. But they are not connected physically at all.
Then you start the DVD and the GS1200 at the same time.
The problem however is that after a little bit...the GS1200's speed would drift. Why? Because it is running the film at 24fps...more or less.. and the DVD is running at 23.97 FPS.
You don't have to worry about the DVD'S running speed. That is constant.
So in order to re-record the easiest way where you are not stopping and starting every 10 minutes or so is to:
1) Make the GS run a perfect 23.97 fps
2)Keep it constant

Pedros NTSC box does both of those things. It has an DIN plug which attaches to the ESS input on the back of the machine and will crystal sync it..meaning keep it at 23.97fps and keep it constant.
The DVD and Pedros box are never hooked up together. Only Pedros box and your machine.
I have tried it with Pedros' older box which ran at 25fps and it locked the GS to that speed. Only problem was I had to keep buying PAL dvds!
If you are using Pedro's NTSC box...it should work. No problem.

Posted by Chip Gelmini (Member # 44) on June 24, 2008, 04:52 PM:

On the way home from Florida, I started thinking and almost stopped at Pedro's to ask if they had any sync boxes available. Assuming they would give me an honest answer that the stock was out, I will ask this group.....where does one get a Pedro's NTSC box? [Big Grin]

Posted by Douglas Meltzer (Member # 28) on June 24, 2008, 07:46 PM:

Pedro's Website

Model P1008GS-DDS is needed to sync a GS-1200 with an NTSC source.

Doug

Posted by Brian Hendel (Member # 61) on June 24, 2008, 10:44 PM:

Wow - $600 without shipping... maybe stopping and starting the GS isn't so annoying after all. I will have to think about this purchase a little more.

Posted by Joerg Niggemann (Member # 611) on June 25, 2008, 05:27 AM:

For those who are a little familiar with electronics: There's an IC "LM 1881" which separates sync pulses from PAL/NTSC Video signals. The TV frame pulse generated by LM1881 can trigger the GS for both PAL and NTSC sources.

The complete circuit only consists of the IC and about 5 external resistors/capacitors. Voltage supply via DIN from the GS. You only need to connect your DVD Player or camcorder as source, and the GS will be truly locked to that source (PAL or NTSC) in ESS mode. If anyone is interested, I can supply a ciruit diagram. Total material costs are about 5 Euro.

Joerg

Posted by Flavio Stabile (Member # 357) on June 25, 2008, 06:58 AM:

HI Joerg,

I'm very interested for the NTSC option... Can you please send me more details?
Regarding the Pedro's Sync Box I want to say that so far I never encountered any problem.
I use it with my ELMO GS PCom and I have re-recorded dozens of Derann movies so far.

thanks
Flavio

Posted by Alan Rik (Member # 73) on June 25, 2008, 07:15 AM:

Hi Joerg,
I am interested in this diagram as well. Please send the details. I am using my computer to generate the 23.97 fps sync for the GS but an external box would be great too.

Posted by Bill Brandenstein (Member # 892) on June 25, 2008, 05:09 PM:

As Brian said, $600 is a lot for the full-deal Pedro treatment. And since I'm familiar with computer audio, I went for the simplest of Pedro's boxes, which requires an external series of tone bursts to lock to. Cost 99 euros and works great from either computer or CD player (audio on L channel, pulse on R). At 48Khz (which is the audio sample rate used for DVDs) 23.976 works out to a beep every 2,002 audio samples. 44.1Khz (for CD) is messy and is better done with a sample rate conversion from 48.

Alan, what do you use to sync from a computer?

This "LM 1881" chip sounds amazing.

Posted by Mark Norton (Member # 165) on June 26, 2008, 01:49 PM:

Thanks for the part No for the diode Kev, but I'm having difficulty finding an axial type capacitor replacement,
If Pedro's sync box is too much, then a cresta interface might be a more affordable option, but I seem to remember you have to make up a box to amplify the signal.

Posted by Joerg Niggemann (Member # 611) on June 26, 2008, 03:15 PM:

I have to correct my statement: The following circuit can be used to sync the GS1200 to PAL Signals. The chip also handles NTSC, but it will not work with the GS because it doesn't convert the frame rate to 23,97. I was wrong with that, sorry. For NTSC, the cheapest way is the "soundcard method".

Here you can find a description of the LM1881 chip.

Joerg

[ June 27, 2008, 01:08 AM: Message edited by: Joerg Niggemann ]

Posted by Bill Brandenstein (Member # 892) on June 27, 2008, 04:22 PM:

Aaarrggh!

Too bad. You good PAL people have it too easy.

Back to the soundcard method.

(Alan, still interested in your setup!)

Posted by Kevin Faulkner (Member # 6) on June 28, 2008, 07:55 AM:

Mark, Which capacitor are you looking for?

Kev.

Posted by Mark Norton (Member # 165) on July 01, 2008, 01:29 PM:

Hi Kev, It's the capacitor Ugo mentions C401, Listed as Polyest Film 0.047mf /50wv. Was planning on replacing both the capacitor and the Zener Diode.

Posted by Kevin Faulkner (Member # 6) on July 02, 2008, 05:04 PM:

Once again a trip to Maplin will sort you. BX74R 0.047 Polyester.

BX74R Capacitor

or DT97F which has longer leads:

DT97F Capacitor

Hope this helps, Kev.

Posted by Winbert Hutahaean (Member # 58) on August 11, 2009, 09:18 PM:

quote:

Pedros NTSC box does both of those things. It has an DIN plug which attaches to the ESS input on the back of the machine and will crystal sync it..meaning keep it at 23.97fps and keep it constant.

This is an old thread, but honestly I am still puzzling about how the Pedro box works.

I am going to ask you again here (a very silly question, may be). If I got the best answer, I may reveal a revolution in sound technology for our 8mm films, which may not require anymore Pedro. I will post it on the other thread.

But now (as my comparison study to my wild idea):

1. As Alan explains above, does it mean if the main source (DVD) has a bit different edit/cut with our 8mm then the sync will totally mess?

2. Do we have to have different Pedro box for PAL and NTSC? or any dual system?

3. To start a DVD (which of course doesn't have any cue/mark), how can we place in sync with the 8mm by frame in the beginning?

4. Ref no. 3 if we start the DVD in wrong place (say by milli second), do we have to stop the projector and redo many times until we get the exact same frame? (how difficult that will be?)

5. During the reel changeover, do we have to do it again (and again) no. 4?

6. For GS1200 with a weak motor, do Pedro box and all sync will still work

I ask with numbers so there is no any miss information. So I do hope you answer too by numbers.

thanks,

Posted by Maurizio Di Cintio (Member # 144) on August 12, 2009, 07:46 AM:

THere we go:

1 - Yes
2 - Yes
3 - You can cue the film in th GS with its button. You can also cue the DVD player with the frame advance facility. For better results, I capture the DVD and post-produce it on NLE to make it suitable for audio transfer: this way I get a a-frame length beep on the original soundtrack which I cause to correspond to a set number on the film head leader. When the Pedro box "senses" the beep via the wire fed into specific connectors (RCA - Cinch) on the box itself, the box slaves the GS from RC standby to rec.

4 - Yes. BUT if you stick to the method described above, there is (almost) no chance you have to do it more than once.

5 - OK I'm talking about redubbing here, on the print's stripes. If uou want to go the PIX/Sound separate way during actual the show, you DO have to prepare a suitable version which takes into account the changeover. This may be a little more convenient if you 'edit' all the reels on bigger reels with no need of changeover.

6 - The Pedrobox works best with a machine up to spec. It only forgives - to the best of my knowledge - minor power problems like the ones described at the beginning of this thread, if necessary by means of an external power supply (Pedroboxes come with a standrad AC adapter which he knows works flawlessly with his gear), necessary if yuo don't want to fix it with soldering iron etc.

Hope this helps

[ August 12, 2009, 10:06 AM: Message edited by: Maurizio Di Cintio ]

Posted by Martin Jones (Member # 1163) on August 12, 2009, 08:46 AM:

Just thrown in as an interesting comment... the IC referred to earlier in this thread (which is easily available) is also used in a number of different published circuits designed for synching projectors to video cameras for "telecine"
transfers at 16.6667 / 25 fps (PAL with three / two blade shutter) and 20 / 30 fps nominal (NTSC with three / two blade shutter).

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