8mm Forum: Chinon 7800H Play/Rewind issue

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Topic: Chinon 7800H Play/Rewind issue

Richard Turner
Junior
Posts: 3
From: Funchal, Madeira, Portugal
Registered: Jul 2016

posted August 02, 2016 07:16 AM

Unless I manually move the floating gearwheel,down to play or up to reverse/rewind it does not automatically happen.

The gearwheel is free to move, nothing is stopping it.

I assume that when play or rewind is selected, the rotation of the main drive gear should move the floating gearwheel down or up by pure rotation.

Anyone any ideas?

The projector has not been in use for 15 years, but everything works OK. [Confused]

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted August 02, 2016 08:58 PM

Welcome Richard! The movement of the gear is mechanically controlled by the main switch to a linkage and the forward or reverse is triggered by a plastic molded cam located beneath the switches in the bottom left. If the gear itself is ok then I would look for a disconnect from the linkage.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Richard Turner
Junior
Posts: 3
From: Funchal, Madeira, Portugal
Registered: Jul 2016

posted August 03, 2016 06:58 AM

Dear Janice

Thanks for the quick reply. But I seem to be going nowhere, fast.
I have stripped out the gearwheels, but I do not trace any mechanical connection?

The wormgear drives / rotates a gearwheel, which is mounted to a spindle that drives a sprocket to feed the film.

The lever which moves the forward/reverse gearwheel is mounted to a brass bush, which the aformentioned spindle goes through.
The brass bush rotates, ok. but it disapears into the cast housing. Perhaps the problem is inside the housing?

Fun, fun, fun !!

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted August 03, 2016 07:39 PM

Ok Richard... some more thoughts [Smile]

After closely observing the gear action...I'm now not sure about the linkage connected to those gears. The linkage I see is only triggering the loop mechanism. The movable gear that moves up for reverse and down for forward looks like it's controlled by the center gear connected to the worm gear. When it turns to the left the movable gear moves down and conversely when the gear turn to the right the movable gear raises. Look at the video to see what you think. Is the direction of the movable gear changing before the main gear starts turning or after [Confused]

https://youtu.be/QTEFfOckXM4

If the movement is not mechanical then the problem might be in the micro switches and possibly the cam that triggers the switch positions. Are the switches working properly in forward and reverse?

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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Richard Turner
Junior
Posts: 3
From: Funchal, Madeira, Portugal
Registered: Jul 2016

posted August 05, 2016 07:34 AM

Fixed it.

The lever which alows the forward reverse action was siezed in it's bush.

I managed to work the lever up and down and in and out whilst spraying with a small amount of WD40 directly onto the bush. After about 2 min. it went loose [Big Grin]

So many thanks for your video and help.

I have now built everything back together and it all works fine.

Best regards from Madeira Island.
Richard

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Janice Glesser
Film Goddess

Posts: 3468
From: Sunnyvale, CA USA
Registered: Sep 2011

posted August 05, 2016 12:36 PM

Fantastic Richard! So relieved that it was a mechanical issue not electrical. This is a very fine projector and made very well. I'm glad the video was of some help.

Take Care.

--------------------
Janice

"I'm having a very good day!"
Richard Dreyfuss - Let It Ride (1989).

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