8mm Forum: GS1200 Sound Tweaks

This is topic GS1200 Sound Tweaks in forum 8mm Forum at 8mm Forum.

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Posted by Paul Adsett (Member # 25) on March 31, 2006, 10:49 AM:

For sometime, one of my GS1200'S, a version 1 machine, has been exhibiting WOW on some of my musical film prints. After much troubleshooting I concluded that some of my films (not all) were in fact slipping at the sound head capstan. Wiping the capstan and rubber roller with alcohol helped, but did not totally fix the problem. When I took a closer look at the sound head area I was very suprised to find that on the GS design the rubber capstan roller only contacts about half way across the width of the film! The reason for this appears to be the presence of the optical track lens assembly, which prevents the roller from being moved in more to get more contact of the rubber roller. Well, I don't show optical track films, and I wanted to see if I could solve the WOW problem, so I unbolted and removed the optical track lens assembly. This enabled me to move the sound capstan rubber roller much further inwards to get better 'bite' on the film. This has totally solved the WOW problem! [Wink]

Then I read Jean- Marc's tip about switching around the 4 little contact pin's on the pressure pad assembly. I took the little cube apart, cleaned and polished all the pins, and switched them around per Jean-Marc's directions. Low and behold- a dramatic improvement in sound quality particularly on track 2! Thank's for that great tip Jean-Marc!

Posted by Tony Milman (Member # 7) on March 31, 2006, 11:14 AM:

Paul

Useful information. Also demonstrates that just owning a DVD projector would not be half as much fun.

Unless of course your name is Mr Quinn [Big Grin]

Posted by Jan Bister (Member # 332) on March 31, 2006, 06:51 PM:

So, Paul.... how much for the optical assembly? I'm still dreaming of adding that to my ST-1200HD... [Roll Eyes]

(Then again it might not even be possible, although the main chassis clearly has all the cutouts and screw holes present to put in an exciter lamp and such...)

Posted by Paul Adsett (Member # 25) on March 31, 2006, 10:18 PM:

Hi Jan,
I think I will hang onto the optical assembly, so that if I ever decide to sell this particular GS I can sell it complete. But right now it stays out of this machine- the mag sound is so much better without it.
Interestingly, I do not have any wow problems on my other GS1200, which is a version 2 machine, so there is still something going on here (film slippage at the sound head) which I cannot fully explain.
[Confused]

Posted by Kevin Faulkner (Member # 6) on April 01, 2006, 11:03 AM:

Paul, It could have just been down to insuffient pressure between the capstan and pinch roller. The pressure has to be about 250g at the point where the pinch roller just leaves the capstan (in forward mode). This is adjusted by raising or lowering the pinchroller solenoid which in turn pulls against a very strong spring. Its possible after some years that this now needs adjusting again.
Also does you pinchroller assay have the ally bush in the centre where it fixes onto the axel or is it just plain green plastic. I have seen the ones with just plain plastic crack where the two fixing grub screws are and that lets the whole assay slip and not give sufficient pressure.

Kev.

Posted by Paul Adsett (Member # 25) on April 01, 2006, 11:35 AM:

Thank's Kev- sounds like good advice. I will check out these two items and see if I can get to the point where I can now move the roller further out and still avoid WOW. Then I may be able to put the optical sound assembly back in place.

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