Canon AT1 with sticky shutter

BetterSense · Aug 16, 2008

I recently inherited a Canon AT1 in great-looking condition with what appears to be the kit lens. After making a silver-oxide replacement battery out of button cells and shrink tubing, it seems to work, and the metering is spot on, but about 10 percent of the time the shutter doesn't seem to work right, resulting in some pretty neat looking photographs with scorched edges, or mostly, the right-third of the photo being a bit over exposed, sometimes also featuring beautiful red auroralike ribbons all over the place.

Since I also vaguely remember experiencing weird shutter lag when these photos were taken, I assume it's the shutter. The mirror cushion foam has all deteriorated and gets on the mirror sometimes, so it's possible that it has gotten in something and gummed it up. The shutter works when it works though, even up to 1000. So I would really like to get it working, cause I was going to leave it loaded with B&W.

Do you know where I could find exploded diagrams? Is there any chance that I could fix this myself? I'm pretty handy with other stuff but never tackled a camera.

elekm · Aug 16, 2008

If the foam has crumbled, it's possible that very tiny pieces have fouled the shutter mechanism, which can be very time-consuming to remove. The shutter definitely isn't running correctly, based on the photo that you've posted. However, it's difficult to say if it's pieces of foam, gummed up lubricant or some other issue.

You could try to repair it yourself, although disassembling an SLR can be tricky. Depending on your skill level, you might be able to service it, or you might end up with a box of parts.

Repair manuals for various cameras often turn up on eBay, and I suppose someone might have one available for free, if one exists.

The "kit" lens in the 1970s was a 50mm lens. Anything else was purchased later or as an alternative. Regarding the battery, I thought that by the time Canon was making its various "A" series cameras, the industry had transitioned to the S76 (LR44, lithium equivalent) battery.

Captain Bedworthy · Aug 16, 2008

I have taken a lot of these apart and the most likely culprit is actually a dirty solenoid on the release side of the second shutter curtain. It's a bear of a job, but the bottom comes off and the solenoids are there. The surface is sticky and needs to be cleaned is my guess. A q-tip and rubbing alcohol is the cure. If the camera makes a loud squeal when the shutter is fired then the solution is a lubrication of the flywheel that dampens the mirror slap. I've done it, but the service is offered here: http://cgi.ebay.com/CANON-REPAIR-A-...NameZWD4VQQcmdZViewItemQQ_trksidZp1638Q2em124

BetterSense · Aug 16, 2008

I read on the intarwebz that using a silver oxide battery was ideal since the discharge curve of the batteries allowes proper metering throughout the batteries life, in contrast to alkaline batteries that have a less-flat discharge. If you've ever taken apart a 6v camera battery, they consist of 4 actual, normal, button cells stacked up and wrapped with cardboard, with stamping on them and everything. So I just made a new battery out of 4 silver oxide button cells, shrink tubing, and the endcaps from the old battery.

The camera does NOT suffer from the squeal, thankfully. It's one of the things I noticed when I used it compared to my Program Plus, was that the photo-taking process was a good bit quieter.

Thanks for the heads up experience regarding the solenoids, at least I have some direction to go in now. I probably won't be able to afford a $100+ repair, although I wish I could because I feel old cameras like this deserve it somehow.

elekm · Aug 16, 2008

This was part of Canon's debut of plastic cameras, the start of a trend that other manufacturers soon followed.

There is a 6-volt lithium, which should work nicely. 4LR44, I think, is the designation, which basically is 4 LR44 cells in a single casing.

I just sold a 1960s Canon breech-mount camera, TX, I think. It was a massive camera. The Canon "A" series was much lighter in weight and felt very nice to use.

I would definitely replace the foam seals before using that camera again.

BetterSense · Aug 16, 2008

I would definitely replace the foam seals before using that camera again.

the 60's breech-mount camera, or my AT-1? You think part of my problem is light seals?

BetterSense · Aug 16, 2008

Here's some more photos.

I found pretty good service manuals here:

Dead Link Removed

with troubleshooting info that says for uneven exposure, clean MG3, which is the solenoid that holds shutter 2 open until it's time to shut it. This is consistent with what I have been told. However I don't know how it could or should be cleaned. I took the bottom cover off and everything seems to be pretty much in order. If there is a problem it must be that shutter 2 sometimes doesn't shut by itself properly. As far as I can tell it's spring-loaded shut and MG3 holds it open, but if MG3 was dirty I don't see how that would cause uneven exposure anyway, just over or under-exposure.

I have tried cycling the camera tons of times without film, and I can't seem to duplicate the shutter lagging, or detect any other problem. Maybe I will shoot another roll and see if it fixed itself. Perhaps it just needed used a bit to get things loosened up, after sitting for so long.

Note not all the photos were bad. The shot of brick for example. The one picture of the table has the left side burnt which is inconsistent with the 'pattern'. Light leak?

cosm670 · Aug 17, 2008

I had an AE-1 (actually a couple) that gave the same sort of overexposed spots in the center of the frame like on some of the photos posted here. It was a simple job of replacing the light seals. Also since the camera is totally battery dependent I would look for a legit battery, the PX28 battery is the 6v one you want for the "A" series cameras

pcyco · Aug 17, 2008

hallo

i also have a at-1. the light seal near the hinge (i hope thats the right word) of the backcover was gone.
i replaced it by a sealingstripe that glazier (i hope also that this the right word) use when they are mounting the glass into the windowframes). now everthing is fine. i replace it one time in the year.
-------------------
thomas

elekm · Aug 17, 2008

BetterSense said:
the 60's breech-mount camera, or my AT-1? You think part of my problem is light seals?

It's always hard to say with any degree of certainty. My feeling is that with any Japanese camera more than 15 years old, the foam seals should always be replaced. If the seals haven't degraded, it's always a matter of "when" and not "if."

The problem isn't necessarily the fact that they degrade but the chance of bits of foam getting into the mechanics of the camera. Then the camera goes from having deteriorating seals to having deteriorating seals and a shutter problem.

In any case, I think some of the other Canon "A" users have some good advice regarding your camera. I don't have enough knowledge about the Canon cameras beyond suggesting replacement of the foam seals. Don't forget to get the mirror bumper too.

If you have some compressed air, you could try blowing out the mechanics with the bottom removed. However, keep in mind that this might have the unfortunate side effect of blowing debris into the viewfinder. Then you have to remove the top deck so you can remove and clean the prism. Under the top deck you'll often find more foam that is used to cushion and/or insulate the circuit boards.

This is how little camera jobs can turn into major overhauls very quickly.

John Koehrer · Aug 17, 2008

Replacing the seals is cheap and easy. If you press the current seal & it either fails to rebound quickly or if it appears "gummy" it's time to replace.
Cleaning Mg3 Is easy, cut about 1/8" off the end of a dollar bill and using the small section dip it in rubbing alcohol, open the magnet, insert the $, close the magnet and putting light pressure on the magnet pull the $ out. Two things are working here. The solvent and the texture of the paper working like a very fine file. You should repeat this a couple of times just to make sure it's clean.

BetterSense · Aug 17, 2008

I developed my two rolls. The really bad shutter problem seems to be gone, but I might still have some light leakage around the edges. I bough a new foam seal kit. I blew the inside of the camera out with canned air too. I'm pretty happy with how nice the pictures turned out. Manual cameras aren't that bad, cause you can kind of 'pre-set' the camera to the ambient light and then pretty much shoot spontaneously with only maybe a little bit of correction. I was shooting some go-karts and I would like get the camera set up and focused on one spot on the track, then shoot people when they drove through it. Turned out pretty good. I hope it keeps working cause I'm totally keeping it full of Kodak c41 B&W.

Nick Merritt · Aug 20, 2008

Keep us apprised. I have a couple of these and they are really nice cameras, so your work is well worthwhile. The FD lenses are terrific, and real bargains today.

BetterSense · Aug 20, 2008

http://flickr.com/photos/29315038@N02/sets/72157606800701981/show/

I took these with fuji 200 color and kodak b&w

Canon AT1 with sticky shutter

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