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Thread: Troubleshooting an erratic Compur 3 electronic shutter (video)

  1. #1

    Troubleshooting an erratic Compur 3 electronic shutter (video)

    Here is a lens I just bought with the compur electronic shutter.

    When it fires correctly speeds (the long ones at least which I can easily measure) work fine. But it fires erratically. Sometimes it does fire properly and the shutter stays open for as long as I have set it to sometimes it just reverts to the default 1/125 speed.

    See this video I shot. It is set at 4 seconds. When I fire it doesn't obviously stay open for four seconds. If I try a second or third time it will fire correctly sometime. But the behaviour seems erratic. I haven't noticed a pattern on when it fails to fire correctly and when it succeeds.

    Do you have any experience?

    https://www.youtube.com/watch?v=McJ9...ature=youtu.be

  2. #2

    Join Date
    May 2012
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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Yes, I have several lenses in #3 and #1 Compur electronic shutters. Their only weak point I have found is the electrical connection to the battery. It must be clean and "sanded" down so there is no contamination for a good electrical connection. A fresh battery also helps and it can be from 4.5V and higher. I do have the service manual for these 1960's electrical devices that pre-date transistors and integrated circuits. This manual is available on the internet. Best of luck.

  3. #3

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Compur electronic shutter has a mechanical default shutter speed of 1/125 sec. These are very reliable and accurate/precise shutters due to their design and construction. Most common problem, batteries, battery connections. Check these first before any other actions. The original battery is a 4.5 volt alkaline that is effectively no longer available. What does work is a modern CR123 lithium battery with a proper size spacer.


    Bernice

  4. #4

    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    I tried cleaning the external contacts of the battery. I still seem to have misfires (at the highest speed) often.

    Also forgot to mention that the T mode doesn't work properly. It opens upon first firing of the lever, but it won't close when re-pressing it. Maybe on problem is related to the other somehow?

  5. #5

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Quote Originally Posted by pureanalog View Post
    I tried cleaning the external contacts of the battery. I still seem to have misfires (at the highest speed) often.

    Also forgot to mention that the T mode doesn't work properly. It opens upon first firing of the lever, but it won't close when re-pressing it. Maybe on problem is related to the other somehow?
    Make sure you totally clean the battery box AND the contacts on the shutter. Use Emory cloth and make them shine like new. If that fails you will have to open up the shutter to see if the internal contacts need re-soldering. It helps if you have a diagram to show you the parts involved.

  6. #6

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Do not use emery cloth. FAR too abrasive unless the grit is above 6000.. Common Emery or similar abrasive paper will rip the plating off causing corrosion of the contacts and other problems over time. Contact cleaner on a cotton swab (q-tip) or at most a pink pencil eraser as the most abrasive cleaning device that is sort of ok.

    Inside the electronic Compur shutter is a gold plated printed circuit board with a set of gold plated contact fingers.These contacts are typically very reliable. If they develop a contact problem it is likely due to ick coating these contacts. If proper cleaning of the battery compartment contacts and battery holder to shutter contacts does not resolve the problem, the shutter speed rotary switch contacts are next. This means partial dis-assembly of the shutter to clean the contacts. Do not attempt this without proper contact cleaner. 100% isopropyl alcohol or commercial formulated contact cleaner with a cotton swab. No abrasive cleaning on the gold plating as this will rip the gold plating clean off. Know there are spring loaded steel balls used as detents and contacts inside the shutters front cover. If the spring loaded steel balls "pop" out, this can ruin your whole day.. no fun at all..


    Quite impressed with the design, construction and quality of materials used in these Compur electronic shutters.. accurate/precise and consistent too.
    Bernice

    Quote Originally Posted by linhofbiker View Post
    Make sure you totally clean the battery box AND the contacts on the shutter. Use Emory cloth and make them shine like new. If that fails you will have to open up the shutter to see if the internal contacts need re-soldering. It helps if you have a diagram to show you the parts involved.

  7. #7

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    For gold plated contacts, I have found that deoxit gold is by far the best solution, both short term as well as long.

  8. #8

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Quote Originally Posted by Bernice Loui View Post
    Do not use emery cloth.
    Bernice
    Excellent point - I just used Emory cloth on the 2 prongs that stick out from the shutter. The use of gold plate means that the designers/builders used the best available materials and that is why these shutters are still functioning after almost 60 years. Why they are not more popular I do not understand. Must be the repair trade who do not want to touch them.

  9. #9

    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    I noticed the following:

    when I keep the shutter release pressed and while holding it pressed I cock the shutter, it never fails to fire at the proper speed. Never...

    What could this mean?

  10. #10

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    Re: Troubleshooting an erratic Compur 3 electronic shutter (video)

    Just bought another lens in Compur Electronic #1 that the seller thought was not working (a camera store no less). Once again these ancient shutters still work perfectly so long as you have a good battery and clean contacts. Paid $60 and was prepared to use it for parts.
    Click image for larger version. 

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