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Topic: Framing Problem with Bell & Howell (Sankyo 700)
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Maurizio Di Cintio
Jedi Master Film Handler
Posts: 977
From: Ortona, Italy
Registered: Jan 2004
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posted August 20, 2016 07:52 AM
Whilst I agree with Andrew there might be room to counteract the wear action, it seems strange to me Melvin didn't mention severe jittery image as the prime symptom of wear on this specific line of machines. Indeed when the shutter cam (that's the name of the part) is worn out on the horizontal plane (the one which does the hardest job), the claw pin will no longer retract to disengage sprockets prior to a new frame-pushing cycle. At the beginning of wear this leads to a slight jitter as the pin struggles to disengage the sprockets but eventually is successful and a new frame can then be dragged. By and by wear becomes more severe, the pin will no longer be able to disengage, stability will become an issue and the loss of the lower loop will get consistent up to the point a film can't simply be watched. In the worst cases sprocket tear might result.
IMHO this is a problem of framing knob assembly registration: for some reason the range of shift allowed by the framing knob is no longer the desirable one. I think Melvin should try to loosen the locking nuts on the framing knob shaft, find the proper range of action and re-tighten the nuts.
If actual cam (or the plastic pin on the claw arm!!!!) wear has occurred, he could loosen the three grub (Allen) screws/bolts which keep the shutter/cam assembly attached to the main shaft, and reposition such assembly 1-2mm backwards. This will cure the problem for some time even though it should be noted, this will cause the ssembly to not work in the best possible conditions (the claw pin might engage the sprockets way too close to the outer edge of the film).
Finally it might be good to re-grease this spot (grease not oil).
Please, Melvin, let us know what you will find out. Best of luck
-------------------- Maurizio
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Melvin England
Jedi Master Film Handler
Posts: 707
From: Hull, East Yorkshire, UK
Registered: Feb 2016
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posted August 27, 2016 04:01 AM
Eventually, I did succeed in removing the two screws as mentioned....a story in itself which I won't go into now. It was such a relief to have the whole unit in my hand an was able to do what I wanted, in a matter of minutes. Basically, I took the plastic cam,turned it 90 degrees and re fixed it to the claw arm,then reassembled it all. I must have put the plastic on the wrong way around as the claw would not come out enough to engage with the sprockets in the film gate. So,I dismantled it,turned the plastic around (keeping it at 90 degrees from its original position as that added a little more lift to the claw arm)then reassembled it. This time the result was what Maurizio expected in the first place.... the claw arm now doesn't disengage with the sprockets! So now I am stumped. I will contact Mr.Van Eck to see if he ever made the replacement part. In the meantime, I ,luckily, have a 2nd identical machine which is running perfectly so,without touching anything mechanical, I will open the back of that one and see if I can compare the two to see if I have overlooked something.
In the meantime, thank you both,once again, for your support and help.
.
-------------------- "My name is for my friends!"
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