Electric Shutter

[John Irvine]

I have a Copal Elec No 1 shutter, currently on a Computar Symmetrigon 6.3/180. Can someone tell me the basics of the electric shutter? It appears to work whether there is a battery in place or not. What are the pros and cons of the electric shutters?

 

[glbeas]

It's powered by the same kind of mainspring as a purely mechanical shutter. You might notice that the speeds don't change when the battery is not in, its running at the fastest speed all the time. The electric part is in the solenoids that slow the shutter down for the slower speeds. The nice thing about this is it gives you some very reliable speeds and the time will go as long as 32 seconds. The bad thing is the battery that comes with it is expensive and seems to go dead just from being in the shutter. I changed the one I had to run on two AAA batteries mounted on the back of the lensboard in holders I got at Radio Shack. The wires ran through a hole sealed with caulk and had crimp connectors on the ends that slid onto the posts that the old battery compartment plugged onto. You could easily do this with a dab of low temp solder for a better connection.

 

[GeorgesGiralt]

Hi John !
I do not know about Copal electric shutters, only Compur electric ones.
The shutter has only one mechanical speed : the fastest one.
When there is a battery in place and the shutter is fired at another speed than the fastest, a solenoid is activated. The blades open and the solenoid prevent them from closing. The time it hold the blades open depends on the speed setting and is given by an RC network and a couple of transistors. When this time has elapsed, current is cut and the blades are released and close.
On the Compur, the battery is used only during the open phase of the movement so it has a very long life. (life is extended by the fact that the shutters fire quite exactly with voltages as low as 3V ).
These electronics are very small (for the period they where made) and use electrostatic sensitive devices. You'd better let the shutter sealed if there is nothing to adjust. One can find some scarce parts for the Compur but I wonder if you can find parts for the Copal...
I wonder why they had not survived up to now and why Copal does not make electronic shutters ? The mechanic part of them is quite simple and straightforward (compared to a mechanically timed one) Afteral all small cameras have electronic shutters these days !

 

[John Irvine]

Very interesting. This shutter has been in storage for over 7 years and the battery still gives 32 seconds on a 32 second exposure. I assume that since the time is generated with transistors not springs, the shutter is accurate at the faster speeds. I'll have to drag out my volt meter and see if it's still 6 volts.

Thanks for the information. I will have to remember the idea about using ingenuity and some AAA batteries.

 

[vet173]

The battery is still available at radio shack as listed for an old mac computer. Have them do a search by voltage as it is unique.

 

[senderoaburrido]

Since they are still largely mechanical, and not completely electronic, do these shutters degrade in the same way all older shutters do? I'm looking at one for sale with a lens, and I have my doubts that the speeds will still be accurate, considering it was last produced 40 years ago.