Compur Electronic 3 shutter - what could go wrong?

[linhofbiker]

I just bought a Super Angulon 165mm from Germany. The lens is in a Compur Electronic 3 shutter. I have been told that these shutters are not reliable and can't be repaired. They run on an old 4.5v mercury battery but can be converted to CR123 with an adapter. I have 3 other lenses in Copal 3 mechanical shutters, so I could put the 165 SA in one of these some time in the future.

My experience with electronic shutters is limited to a Bronica GS-1. The Bronica lenses had a Seiko 0 electronically time shutter that was controlled from the camera body. These shutters never failed, were accurate and were silent during long exposures. I think the Seiko was designed in the early 1980's while the Compur Electronic shutters were designed in the 1970's or earlier. Have circuit boards, integrated circuits and solid state devices changed in that decade or so? The principles that guide an electronic "escapement" aren't that complicated I would think and therefore should be repairable or even replaceable. But I am an optimist and did have some electrical engineering training many years ago.

[Jim Galli]

I've never had one that didn't work. Have you applied 4.5 V from some source and given it a try? Cleaning electrical paths that slide against each other and checking for hard solder joints would be a place to start if it doesn't work. I wonder if an electrical diagram could be had for these. Mr. Salomon, can you help?

[Havoc]

First you have to know what can't be repaired: the mechanics or the electronics? Some electronic components can go bad and are next to impossible to find or find a replacement that could fit. On the other hand, if the schematics and functioning are documented I'm fairly sure some enterprising hobbyist could put a replacement together. Likewise I'm fairly sure that if a correct mechanical piece is available, it could be remade.

[linhofbiker]

Thanks Jim. I have not received the shutter yet and was told it is working. In preparation for its sudden demise I have ordered an old repair manual about Compur electronic shutters, the 1 3 and 5, so hopefully there will be some circuit diagrams to aid in a repair if needed.

[MusicalPhotog]

I have a 300mm Symmar Conv in one... Works quite well. But I have noticed that the time does seem to fluctuate with the voltage applied. For example when running it with a 3v CR2 lithium battery, the speeds sound like they drag a bit (comparing by ear with known good mechanical). So now I'm toying with the idea of wiring a battery holder that holds (3) AAA batteries, in series, for a total 4.5v, to see if that would make a difference. AAA batteries are certainly easier to come by than the 4.5v mercury cells. Has anyone else tried this? Any reason I shouldn't attempt it? (For example: mA value from AAA too high?)

[Havoc]

mA rating has nothing to do with this so it should be safe. What can be a problem is that the voltage over time is different. Mercury cells have a very flat discharge curve, their tension varies little while they are used and then go fast low at the end of life. Alcaline cells have more drop along their life compared to mercury.

If the shutter speed depends on the voltage, then a couple of alcaline cells and a small voltage regulator would be a better solution. Some low drop regulator could be used. But it would be best to first measure the current used during an exposure to make sure this setup works. If it actuates some coils, then the current demand can be rather high during a short time. And you have to make sure you can supply it.

[Bob Salomon]

I've never had one that didn't work. Have you applied 4.5 V from some source and given it a try? Cleaning electrical paths that slide against each other and checking for hard solder joints would be a place to start if it doesn't work. I wonder if an electrical diagram could be had for these. Mr. Salomon, can you help?

Sorry, no. They were not available when I sold Linhof and our service center didn’t handle them.

[domaz]

mA rating has nothing to do with this so it should be safe. What can be a problem is that the voltage over time is different. Mercury cells have a very flat discharge curve, their tension varies little while they are used and then go fast low at the end of life. Alcaline cells have more drop along their life compared to mercury.

If the shutter speed depends on the voltage, then a couple of alcaline cells and a small voltage regulator would be a better solution. Some low drop regulator could be used. But it would be best to first measure the current used during an exposure to make sure this setup works. If it actuates some coils, then the current demand can be rather high during a short time. And you have to make sure you can supply it.

A really crude solution to voltage drift would be to use a higher voltage battery pack (2 cell lithium perhaps which would be ~7.2v) then attach that to a 4.5v voltage regulator. The only drawback is you would need a switch between the regulator and battery as it would tend to draw current even when not in use I suspect.

[Gary Beasley]

I have a 300mm Symmar Conv in one... Works quite well. But I have noticed that the time does seem to fluctuate with the voltage applied. For example when running it with a 3v CR2 lithium battery, the speeds sound like they drag a bit (comparing by ear with known good mechanical). So now I'm toying with the idea of wiring a battery holder that holds (3) AAA batteries, in series, for a total 4.5v, to see if that would make a difference. AAA batteries are certainly easier to come by than the 4.5v mercury cells. Has anyone else tried this? Any reason I shouldn't attempt it? (For example: mA value from AAA too high?)
I wired an electronic compur up with two aaa in series, mainly because thats all the battery holders I had at the time and it worked great. I never checked the accuracy but seemed to time quite well just from observation.

[aphcl84]

These are in my experience extremely reliable shutters that generally either work perfectly or not at all when something is wrong. They can run as per the manual on 2.5-6v power so battery compatibility is pretty easy to manage, I use a cr123 with a aluminum spacer for my shutters. The mechanics of the shutter are very simple and share a number of parts with the non electronic compurs so parts availability is not that difficult. And the electronics are also quite simple consisting of 5 small transistors, two capacitors, two variable pots and 22 resistors. All of which could be replaced with modern equivalents. The shutters do use a small amount of power at all times though so be sure to remove the battery box when not using it.

[Paul Ewins]

I bought a reproduction repair manual from here: http://www.photobooksonline.com/books/shuttersrepair.html (#8183). It is basically a single speed (1/125) mechanical shutter that has an electronic delay added on to achieve the slower speeds. So 1/60 is 1/125 shutter + 1/115 delay, 1/30 is 1/125 shutter + (1/115 + 1/60) delay and so on (the math makes more sense in decimals than fractions). The speed change is governed by resistance with individual resistors for each speed so that part is repairable.

[Havoc]

It are not the resistors that will have issues but the capacitors. They can turn bad.

[linhofbiker]

My shutter with lens arrived yesterday from the Ebay seller in Wien Austria. The battery container had a spacer that worked with a CR123 3V battery. I put a battery in it but the cover kept popping off, so I found 2 O-rings that hold it in place. The shutter works like a charm. The other lens, a 165 SA, is supposed to arrive today. It has a battery holder, but I think I will use the same modified battery holder with it too. As advised I will keep the battery holder off the lens when not in use. BTW it is nice to have a mechanical speed of 1/125 (or, 1/200?) available when the battery holder is removed.

I hope to mount my 19" f/11 apochromat(red dot)artar in barrel in the first shutter, even though I may loose half a stop or so. The rear element unscrews but the front element will not budge. When I do get it off I am hoping it will fit into the shutter. The front element has 3 set screws just in front of the aperture setting ring and I assume they are preventing the front element removal. Also, the barrel has an opening for some kind of filter and has a lever that will close the opening completely.

[Louis Pacilla]

I hope to mount my 19" f/11 apochromat(red dot)artar in barrel in the first shutter, even though I may loose half a stop or so. The rear element unscrews but the front element will not budge. When I do get it off I am hoping it will fit into the shutter. The front element has 3 set screws just in front of the aperture setting ring and I assume they are preventing the front element removal. Also, the barrel has an opening for some kind of filter and has a lever that will close the opening completely.

I assume you know this is not going to be a direct fit so are you going to cut & machine the threads your own tubes and if not are you sending them to SK Grimes? If your sending them off you may want to send the barrel along with the cells so Adam will know the proper spacing and all. They will return the barrel back once cells are mounted.

[Bob Salomon]

My shutter with lens arrived yesterday from the Ebay seller in Wien Austria. The battery container had a spacer that worked with a CR123 3V battery. I put a battery in it but the cover kept popping off, so I found 2 O-rings that hold it in place. The shutter works like a charm. The other lens, a 165 SA, is supposed to arrive today. It has a battery holder, but I think I will use the same modified battery holder with it too. As advised I will keep the battery holder off the lens when not in use. BTW it is nice to have a mechanical speed of 1/125 (or, 1/200?) available when the battery holder is removed.

I hope to mount my 19" f/11 apochromat(red dot)artar in barrel in the first shutter, even though I may loose half a stop or so. The rear element unscrews but the front element will not budge. When I do get it off I am hoping it will fit into the shutter. The front element has 3 set screws just in front of the aperture setting ring and I assume they are preventing the front element removal. Also, the barrel has an opening for some kind of filter and has a lever that will close the opening completely.

That slot is not for filters. You bought a process lens and they accepted drop in disks to create different dot patterns for the print presses.

[linhofbiker]

That slot is not for filters. You bought a process lens and they accepted drop in disks to create different dot patterns for the print presses.

Thanks Bob. A process lens is designed for closeups. Does the spacing differ when used at infinity. I seem to recall that the spacing on a Componon-S was different than the Symmar-S equivalent, although for most practical purposes it made no difference.

The Compur Electronic 3 has M 58x0.75 front and rear with M 62x0.75 thread for retaining ring. Is this pretty standard? If the barrel elements don't fit then I will have to send it all to SK Grimes.

[Dan Fromm]

A process lens is designed for closeups. Does the spacing differ when used at infinity.

You'll get conflicting answers. The ones I like are that it depends on the lens and that process dialytes (Apo-Artars, dialyte type Apo-Nikkors, Apo-Ronars, Repro-Clarons) are optimized for 1:1 and hold their corrections very well to infinity.

I can't find it but I vivid recall reading a piece of Rodenstock propaganda that insisted Apo-Ronars performed better at infinity than any telephoto lens of the day.

[linhofbiker]

196621196622Recently obtained some more:196619196620196621

1) 165mm f/8 Super Angulon in Electronic 3
2) 75mm f/5.6 Super Angulon in Electronic 1
3) 150mm f/5.6 Componon in Electronic 3
4) 210mm f/5.6 Symmar-S in Electronic 3 (inserted my cells)

[Pere Casals]

Recently obtained some more:

Those shutters operate the coil with two voltages. They need a short impulse at high voltage to open at its max rated speed, but this impulse has to be short because that high voltage ¡s around x4 times higher that the one (nominal) it can be resisted by the inner coil in a long period. Then voltage drops to the level that simply holds the shutter open, that it can be 1/2 of the coil nominal voltage.

[linhofbiker]

Those shutters operate the coil with two voltages. They need a short impulse at high voltage to open at its max rated speed, but this impulse has to be short because that high voltage ¡s around x4 times higher that the one (nominal) it can be resisted by the inner coil in a long period. Then voltage drops to the level that simply holds the shutter open, that it can be 1/2 of the coil nominal voltage.

Is this good old 1950's and 1960's technology? All 4 examples I have run without battery at the max mechanical speed. Using a 4.5 volt battery all speeds function as intended. My original post was about "what could go wrong" in anticipation of trouble. I have the Compur manual of how to service these shutters, but so far all are working fine. As was suggested I keep the battery container off the lens until it is needed. I have two good battery containers and one that needs work, but I only need one since I only use one lens art a time.

The Compur repair manual shows what should be lubricated and what "grease/oil" should be used - supplied by Compur themselves. Does anyone know what type of "grease/oil" was specified and what modern substitute should be used instead. As a precaution I would like to lubricate all shutters since I don't know their history. Or is this playing with fire?

[Pere Casals]

what modern substitute should be used instead.

I use this one for the internals of old Compur shutters, with total success:

196623

https://www.amazon.com/Interflon-Fin-Super-Aerosol-300/dp/B074Z3VZLC/ref=sr_1_1?keywords=interflon+fin+lube&qid=1571330468&sr=8-1

It is a thin layer dry teflon lubricant, it has a solvent that evaporates leaving a layer of polarized teflon particles. Make the mechanism work just after application (while solvent still there) to expel dirt.

I've lubricated with that 3 old Synchro Compur shutters, some 4 years ago. Checked with a shutter tester, right now they all perform as they should.

Instead, I tried the same with two Seiko shutters with less luck, they improved buy still they don't work fine.

[linhofbiker]

I use this one for the internals of old Compur shutters, with total success:


Thanks, I will get some. Do you have to dismantle parts or do you apply as-is?

[Pere Casals]

I disassembled the 1st one, 2nd and 3rd were simply lubricated from the speed lever notch.

[Oslolens]

I had a Compur electronic #3 on my Symmar 300mm. For battery, I found a 4.5 volt on ebay with correct dimensions. Do not know how long it lasted, as I sold the lens.

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