Tricky Compur Shutter

adamlikesbikes · Sep 18, 2021

Hello all. I've got a Synchro-Compur P shutter that I'm attempting to get running again. The issue is that after cocking and firing the shutter, the diaphragm stays shut until I apply pressure on the cocking ring, after which it fires at the chosen speed.

Any insights into what may be causing the hesitation in the firing action would be greatly appreciated.

shutterfinger · Sep 18, 2021

While I'm familiar with Synchro Compur shutters I'm not familiar with the P version.
This instruction manual https://www.butkus.org/chinon/booklet/synchro-compur_shutter/synchro-compur_shutter.htm uses a picture of the P but the operation instructions apply to a standard Synchro Compur.
Your problem is most likely due to dried lubrication. A full teardown CLA should fix it.
Its likely a CN-1307-000. https://learncamerarepair.com/downloads/pdf/Compur-Factory-Shutter-Repair-Manual.pdf
I have used this manual to repair shutters not listed in the lens/camera section and Compur Rapid shutters as they are similar, top plate may be one shutter model, bottom plate a different model. Even if you don't find an exact match there should be one or two that are close matches. Take lots of good pictures as you disassemble it as they will be an asset for reassembly.

adamlikesbikes · Sep 18, 2021

Thanks for the amazing response! I've actually been using that exact guide for the CN-1307-000 as well as a few other sources and I could probably reassemble the shutter blindfolded but I haven't touched on lubrication yet.

What would clearing the dried lubrication entail?

gone · Sep 18, 2021

It's probably exactly as shutterfinger said, and/or something could be bent as well. It sounds like you've already opened the shutter up. If that's the case, then it's time to tear it all apart for a good clean, and look closely w/ a magnifying glass to see if there's any dried lubricant in there or anything else that looks wrong. There's different opinions on lubricant, but mine were never lubricated, they ran dry just fine.

Thankfully, I've never had to fully disassemble a shutter. Mine were brought back to life w/ just a squirt of lighter fluid and firing the shutters at all speeds frequently.

shutterfinger · Sep 18, 2021

I use 90% Isopropyl Alcohol and CRC QD Electronic cleaner. Soak the parts in the alcohol for 5 to 30 minutes then wipe with cotton swabs and paper towels. I use the alcohol in a ultrasonic cleaner for jewelry.
I use TriFlow oil on the pivots and Finish line Fett grease for sliding parts. A drop of the oil about the size of a straight pin point is all that is needed. A trace of grease is all that is needed.
https://www.amazon.com/Tri-Flow-Squ...id=1631990301&sprefix=triflow,aps,250&sr=8-18
https://www.amazon.com/Finish-Line-...90421&sprefix=finish+line+fett,aps,215&sr=8-2

adamlikesbikes · Sep 18, 2021

Thanks! I'm sure it's absolutely the lubricant because after exercising the shutter for a bit it works without hesitation.

I don't have an ultrasonic but I'll give everything a bath in isopropyl for sure. I'll order the triflow and grease asap because I want to get this lens into the field!

shutterfinger · Sep 18, 2021

Check your local bike shop or hardware store for the lube.
Be careful removing/installing 693,694, 664 as they are easily bent and difficult to bet back to original shape and working correctly.
No need to remove the springs from 664.
Do not release the tension on the delay timer as 1 gear tooth on 314 will make the difference between all speeds from 1 second to 1/100 being in tolerance or just some of them in tolerance.

adamlikesbikes · Sep 18, 2021

Thank you for for additional info. I found some triflow at my bike shop and applied it after bathing parts in isopropyl and it certainly runs much smoother now.

If you're at all familier with synchro compur mechanisms could I pick your brain about adjusting the shutter speeds? The slow speeds (1, 2, and 5) are all significantly off, while the faster speeds are quite compareable to my other shutters which have recieved proper CLAs. Do you know how to position the retard gear train to speed up the slower speeds?

shutterfinger · Sep 18, 2021

See Tafel 8 of CN-1307-000 and check the distances shown in fig 1 then recheck the fig 3 distance.
Basically the closer the 305 is to the center of the shutter the faster the slow speeds. If 305 (P fig 1, tafel 8) is too far from the shutter center the shutter will not run on slow speeds.
With the delay timer removed press 302 to the end of its travel while holding 305 from moving then slowly allow 305 to travel until it disengages from 314 without letting 314 from loosing its existing tension then turn 314 1 or 2 gear teeth at a time from its tension position then reengage 305 and retest the speeds. Easier said than done. Sometimes one has to settle for a happy medium as the coil tension spring attached to gear 314 weakens. The spring is like a watch mainspring.

adamlikesbikes · Sep 19, 2021

I don't quite thing that I follow. Starting with yout first step, does 302's "end of travel" place it into it's centermost position?

shutterfinger · Sep 19, 2021

look at figure 1 on page 8 cn-1307-000. The post on 305 should be at the end of its travel, as close to the outer edge of the shutter case. you may have to push 302 toward the outer edge of the case to move 305 but 302 otherwise rests on the cocking ring with the cocking ring in the full release position.

adamlikesbikes · Sep 21, 2021

Mr. Shutterfinger I owe you a few beers.

After countless adjustments I have the speeds in sync (or close enough) with my other shutters and that'll do for me.

Thank you so much for your help

shutterfinger · Sep 21, 2021

Your welcome. A Coke Zero or two will suffice if we meet.

Tricky Compur Shutter

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