View Full Version : Can I replace a Compur 3 electronic to a Copal 3?

13-Apr-2013, 08:30
I bought a lens on a compur 3 electronic 3 shutter that is running slow. Could I substitu it with a Copal 3? The lens is f8 and most copal 3 are 5,6, would that be a problem?

Thank you.

Bob Salomon
13-Apr-2013, 09:24
Copal can be any aperture. You just change to the correct aperture scales. They are screwed on so they are easily changed. However you may need someone to calibrate a blank scale set if the correct scales are no longer available from the lens manufacturer.
A camera repair technician can make the new scales, but then they can probaly do a CLA and that may fix your Compur.

13-Apr-2013, 12:14
Thanks for the answer Bob. Are Compur still easily fixed? Or is it better to just go for a Copal?

Bob Salomon
13-Apr-2013, 12:23
Thanks for the answer Bob. Are Compur still easily fixed? Or is it better to just go for a Copal?

Prontor Werke discontinued the production of all mechanical shutters a couple of decades ago. Copal discontinued manufacturing mechanical shutters last year. It is already difficult to get some Copal parts new. Virtually impossible to find new Compur parts.

That said, service people save scavanged parts. So your shutter can possibly be repaired by a good service center. However, it may only need the CLA as it is a prettu old piece of equipment and probably hasn't been serviced in multiple decades, if ever.

Paul Ewins
13-Apr-2013, 18:36
The Compurs (and I believe most other electronic shutters from that era) have one mechanical speed which is the fastest speed. All of the other speeds are achieved by delaying the closing of the shutter i.e 1/125 = 1/125 (fastest speed) + no delay, 1/60 = 1/125 + 1/125 delay, 1/30 = 1/125 + 3/125 delay, 1/15 = 1/125 + 7/125 delay and so on. The varied delay is achieved by varying resistance. Most of the other old electronic shutters used an external control box to achieve this, but the electro-compurs have a PC board inside the shutter with tiny surface mounted resistors. As you move the shutter speed ring a contact moves from one resistor to the next. If all of your speeds are slow, including the fastest speed, then it might be an issue with the mechanical side of the shutter. If only some of the speeds are faulty then it might be that the contacts on the PC board are dirty. If it is the resistors that are faulty then you are probably out of luck since the PC board was designed to be a replacement part and not repairable. If you are a tinkerer and enjoy playing with electronics then maybe you could make an external control box to bypass the PC board. If, however, you just want a lens to use then swap the elements to another shutter.

14-Apr-2013, 01:16
Wow Paul many thanks for that info. I got the lens and it states the the speeds 1/15, 1/8, 1/4.... Are quicker to the ear of the seller. When I do receive it I will double check and see what is really happening. Im not much of an electronic but I do have a close friend which is great at it. And will see if we can do something about it. If its to hard or not possible to mend I probably will get a Copal 3 to substitute.

Thanks again for all the answers.