This is topic Sankyo 702 rewind problem in forum 8mm Forum at 8mm Forum.

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Posted by Jason Moffatt (Member # 4416) on October 02, 2019, 05:45 AM:
I have just picked up one of these and with 600 ft reels the rewind grinds to a halt before it has fully rewound.How do you adjust the torque ?.Also i have a sankyo stereo 800 and the yellow lever on top is lifted upwards to rewind but the same lever on the 702 does nothing, it just springs back down when you try to lift it.Is it supposed to do the same thing as on the 800 ?
Posted by Jason Moffatt (Member # 4416) on October 05, 2019, 03:50 PM:
Ok let me try another way.If anyone has a sankyo 702 can they have a look to see if the orange lever on top above the lens that flips upwards is supposed to do anything as mine does not, it just springs back down.
Posted by Jim Schrader (Member # 9) on October 05, 2019, 07:49 PM:
While I don’t have one of these units I just googled it and am looking at pictures could it be a threading mechanism?
Posted by Janice Glesser (Member # 2758) on October 05, 2019, 08:53 PM:
Jason...that lever on the Sankyo 800 really doesn't do anything you can rewind without raising it. I have seen this "R" lever also on other Sankyo projectors like the 1000 and the 2000H. The lever doesn't seem to enhance nor inhibit the rewind process. I don't have a 702...but my guess is that rewind lever is not a "feature" on that model.

Specifically what problem are you having with the rewind?

[ October 06, 2019, 01:58 PM: Message edited by: Janice Glesser ]
Posted by Jason Moffatt (Member # 4416) on October 06, 2019, 10:00 AM:
As mentioned I also have a stereo 800 and the same lever flips upwards and it stays there.It gives a more positive rewind as it somehow locks the gears together, also it has an “R” stamped on it meaning rewind.

But on the 702 the same lever does not stay in the raised position,it just springs back down again and also it doesn’t seem to lock any gears together.Also It does not have an “R” stamped on it.If this lever does nothing on this model why include it?.The rewind on my 702 is ok for up to 400ft reels but 600ft reels it grinds to a halt near the end.
Posted by Maurice Leakey (Member # 916) on October 06, 2019, 11:55 AM:
I know this sounds a silly question, but are you setting the main control to reverse before you lift up the front yellow rewind catch?
If you are doing this correctly but still having trouble then it seems there is an internal problem.
Posted by Bill Harris (Member # 5473) on October 06, 2019, 12:32 PM:
No, the yellow lever on the 702 does not do the same rewind function as on the 800. I have used both models.
Posted by Janice Glesser (Member # 2758) on October 06, 2019, 01:59 PM:
It sounds like on the 702 that part is just a feed guide.
Posted by Maurice Leakey (Member # 916) on October 06, 2019, 02:42 PM:
And yet, it pivots.
Posted by Janice Glesser (Member # 2758) on October 06, 2019, 05:04 PM:
I don't know for sure...but it could be that Sankyo used the same part as on the 800. That part just slides onto a metal post like the front panel knobs do. However the metal post on the 702 is attached to a spring and doesn't lock in an upward position like the 800.
Posted by Jason Moffatt (Member # 4416) on October 06, 2019, 05:33 PM:
I’ve just taken the back cover off and had a look inside and there is nothing attached to the lever on the inside to move the cogs so it does not seem to serve any purpose, unless somethings missing.Also i can’t see a way to adjust the torque for rewind as it struggles with larger reels.
Posted by Nantawat Kittiwarakul (Member # 6050) on October 06, 2019, 07:30 PM:
Had you already checked the belt in the reel arm? I bet it had stretched beyond use.
Posted by Maurice Leakey (Member # 916) on October 07, 2019, 01:54 AM:
I have had an overnight sleep and it all comes back to me now !!!

The yellow guide at the film entry hinges up to allow manual unthreading of the projector. This gives clearance for the film to come clear of the sprocket. This applies to most Sankyo models. Rewinding is simply an act of turning the control knob to reverse.

The 800 model takes 800ft spools. No doubt the makers thought that the motor could not do a rewind of the larger spools without additional assistance.
Posted by Jason Moffatt (Member # 4416) on October 07, 2019, 02:47 PM:
Just had another look and yes the film will not come out without lifting the lever.I would imagine it must mention this in the manual also.
Posted by Maurice Leakey (Member # 916) on October 08, 2019, 02:33 AM:
I've got a 702 but no original box or instructions. However, I do have a Bell & Howell DCR which is a Sankyo. This is all complete and with the instruction book in multi languages. The book clearly states what I said above regarding rewinding and shows the method of how to remove an already laced film. If you want manuals they are available from Oldtimer Cameras.

Your trouble may be stretched belt/s as per the comment above by Nantawat.
Posted by Brian Fretwell (Member # 4302) on October 08, 2019, 10:45 AM:
Strangely by Sankyo 301 has the most powerful rewind of any 8mm machine I have, there must be a drive belt or problem. I assume the back spool turns freely during rewind.
Posted by Jason Moffatt (Member # 4416) on October 09, 2019, 05:14 AM:
I’ve opened the back up and had a look while rewinding a large reel.The belt is ok, it’s not slipping but there is what looks like a cork slip clutch which is slipping and its all held on by a C clip and i can’t see a way of increasing the torque.
Posted by Maurice Leakey (Member # 916) on October 09, 2019, 06:04 AM:
Why don't you buy the Repair Manual from Oldtimers as mentioned above, no doubt it will give you some answers.
Posted by frank arnstein (Member # 330) on October 11, 2019, 05:17 AM:
I had the same annoying problem with my Sankyo 702 till I found the cause and fixed it. You can fix your machine too.
This is a known weakness in all Sankyo 300, 500 & 700 series.

You have already zeroed in on the problem. It's the rewind clutch assembly and it is slipping much earlier than it should. But its not slipping properly so it can't do the job as expected.

You will have to remove the C clip and the washers beneath it. Then slide or wiggle the clutch assembly off the shaft.
The unit has 2 steel drive washers and they have a cork washer between them.

The 2 steel washers have a small locating hole on them which coincides with a small plastic drive dimple on their driving gears. These dimples can break off and then the steel washer will begin to spin under load instead of driving the cork washer. The clutch should slip on the cork faces and not spin together with the washers.

Remove the C clip holding the steel washers and cork together and then look for the broken locating dimple on the plastic gear. Using super glue, glue the steel washer to the drive gear where it originally was. Reassemble the clutch with the cork between the washers and ensure it slips on the cork faces when tested.

Refit the assembly and test forwards then rewind. Use your hand on the rewind spindle to determine the power of the rewind torque. It should now be normal torque available for rewind and reverse project.

Jason, Let us all know how you go fixing your Sankyo 702.

these Sankyos don't have any stretchable rubber belts in the delivery arm. They have plastic gears and you can't open the arm to service it.

the rewind levers you mention on the Sankyo 1000 and 2000h series do actually engage a small plastic dog clutch when pulled out. This is supposed to prevent clutch slip when rewinding a full heavy reel. These clutches do actually work when properly cleaned and lubed.

regards to all
dogtor frankarnstein

[Wink] [Razz] [Smile] [Wink]
Posted by Nantawat Kittiwarakul (Member # 6050) on October 11, 2019, 07:56 PM:
Gee, so that's literally Elmo's design - so to speak of.
Some low end Yelco's did have only slip clutch for both reverse/rewind, and it's near impossible to get the optimum settings for both operation. Some compromise had to be made. [Roll Eyes]
Posted by Burton Sundquist (Member # 5813) on October 13, 2019, 12:51 AM:
Thanks Dogtor Frankarnstein for your post. I think this will help Jason. If I am right and the Sankyo 702 has the same clutch gear as my Sankyo 800, here is what it looks like (exploded view)


Thanks to Dogtor F. I found a solution for my clutch gear too! But there is more information Jason. If your 702 will have this cog wheel to the right of the clutch gear, and I bet it does, you can adjust the torque of take up/ rewind.


If you have the cog/gear shown here to the right of the removed clutch gear you will see that it has a double nut retainer. If you loosen the back nut and tighten the front nut one turn, your take up and rewind torque will easily handle a 600' reel. My 800 model was modified to handle 1200 ft. And works great! I noticed that the take-up was getting sluggish so The Dogtor came through for both me and you! Try this torque adjustment, I am sure it will solve your problem and the projector will perform as it should, just fine.
And Frank, I did open the arms of the Sankyo Stereo 800 but required more super glue when all was accomplished.
Posted by Jason Moffatt (Member # 4416) on October 13, 2019, 05:44 AM:
Thanks for the very informative posts.I will give it a try and report back.
Posted by Jason Moffatt (Member # 4416) on October 16, 2019, 05:57 AM:
Ok, i’ve just had a go and all went well.It now easily rewinds a 600ft reel.The hardest part was putting back the small top C clip while at the same time trying to compress the curved spring washer.Now to find another projector to fix, this is very addictive i probably have around 20 working machines now. Thanks everyone for the help.
Posted by Burton Sundquist (Member # 5813) on October 18, 2019, 12:37 AM:
Very good to hear! I have found this forum to offer the best advice concerning projector repairs. If it's non-electrical I am okay. Repairing a 40 year old projector is unique and requires skill. You should be proud. And it is challenging which makes it fun. That last spring washer and c clip is the hardest part but well done!...20 machines? Curious to what they might be!

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