Canon A1 - stuck meter reading

hamberger · Oct 5, 2016

Hello all, first post!

I just got a Canon A-1 in excellent cosmetic and mechanical condition, however there seems to be something wrong with the meter: it appears to be stuck on a certain light reading.

Whether aperture priority or shutter priority, the camera calculates the adjustments correctly when I change them, but shows the same brightness reading regardless of the light.

For instance pointed at a lightbulb or the sun and then with the lens cap on have the same exact same rating: with lens cap on and set to 400ASA it shows 1/1000 & f13

Also batteries are brand new, but I tried the old ones that were in it and they show the same reading

I'm guessing I need to open this baby up? Anyone have any experience with an issue like this?

flavio81 · Oct 5, 2016

hamberger said:
Hello all, first post!

I just got a Canon A-1 in excellent cosmetic and mechanical condition, however there seems to be something wrong with the meter: it appears to be stuck on a certain light reading.

Whether aperture priority or shutter priority, the camera calculates the adjustments correctly when I change them, but shows the same brightness reading regardless of the light.

For instance pointed at a lightbulb or the sun and then with the lens cap on have the same exact same rating: with lens cap on and set to 400ASA it shows 1/1000 & f13

Also batteries are brand new, but I tried the old ones that were in it and they show the same reading

I'm guessing I need to open this baby up? Anyone have any experience with an issue like this?

Welcome to the forum Hamberger from Kentucky. Which, coincidentally, are my favorite foods (Burgers & KFC)

This could happen if the exposure lock button contacts had got stuck, so it's the first place to review. You turn on the camera, the exposure system 'memorizes' the actual light value and it immediately gets locked. So it's very likely that this button is stuck in the "connected" position.

And for servicing that contacts i think you don't need to open up the whole camera, just the plastic framing around the lens mount.

And of course i don't need to point you which one is the exposure lock button, since you're a nice guy and thus you must have read the whole Canon A-1 user manual.

This is a great camera, at least great if you are comfortable in the automatic modes. Some of my best photos were made by a Canon A-1. Now i use the F-1 models.

hamberger · Oct 5, 2016

flavio81 said:
Welcome to the forum Hamberger from Kentucky. Which, coincidentally, are my favorite foods (Burgers & KFC)

This could happen if the exposure lock button contacts had got stuck, so it's the first place to review. You turn on the camera, the exposure system 'memorizes' the actual light value and it immediately gets locked. So it's very likely that this button is stuck in the "connected" position.

And for servicing that contacts i think you don't need to open up the whole camera, just the plastic framing around the lens mount.

And of course i don't need to point you which one is the exposure lock button, since you're a nice guy and thus you must have read the whole Canon A-1 user manual.

This is a great camera, at least great if you are comfortable in the automatic modes. Some of my best photos were made by a Canon A-1. Now i use the F-1 models.

Hello Flavio81 - thank you for the reply!

And yes, I frequently get blamed for my name causing folks to get hungry

The exposure lock button makes a lot of sense, however I was under the impression it would only lock exposure while the button was held, with the LED's remaining lit?

Also, any recommendations on servicing the contacts?

flavio81 · Oct 5, 2016

hamberger said:
Hello Flavio81 - thank you for the reply!

And yes, I frequently get blamed for my name causing folks to get hungry

The exposure lock button makes a lot of sense, however I was under the impression it would only lock exposure while the button was held, with the LED's remaining lit?

Also, any recommendations on servicing the contacts?

The EL button locks exposure and as far as i can recall it does it even if you don't hold any other button. It is independent.

For the contacts, take a look at them, clean, etc.

hamberger · Oct 5, 2016

flavio81 said:
The EL button locks exposure and as far as i can recall it does it even if you don't hold any other button. It is independent.

For the contacts, take a look at them, clean, etc.

So I was able to remove the plastic framing around the lens mount and get a good view of the contacts for the Exposure Memory and Exposure Preview

Unfortunately looks like that wasn't the cause of the problem - everything looks in place, super clean and LED is registering the contacts

So I guess I will have to disassemble it a bit more, I'm just not sure what to look for at this point.

Would it be accurate to assume the problem is in the sensor itself or even the computer?

flavio81 · Oct 5, 2016

hamberger said:
So I was able to remove the plastic framing around the lens mount and get a good view of the contacts for the Exposure Memory and Exposure Preview

Unfortunately looks like that wasn't the cause of the problem - everything looks in place, super clean and LED is registering the contacts

So I guess I will have to disassemble it a bit more, I'm just not sure what to look for at this point.

Would it be accurate to assume the problem is in the sensor itself or even the computer?

Which is the exposure value that you get? Is it a very very dark exposure value?

Also, can you try turning off the camera, then pointing at the scene and then turning on the camera, so you can see the acquired exposure value. Is this exposure value appropriate for the scene?

I wouldn't fault the computer at all. If it was faulty you wouldn't get the LED readings.

On electronic cameras most such faults are down to silly things like bad solder joints (google "cold solder joint"), bad contacts. Light sensors, particularly the SPD sensors used on those cameras, are unlikely to fail by themselves.

farmersteve · Oct 5, 2016

I bought an A-1 lens bundle off of ebay for the lens and was told the camera wasn't working so I only really paid the going price for the lens, the body was essentially free. I got it and the damn camera looked like the day it was made but the shutter wouldn't fire. I pulled the bottom off and tried fiddling with the magnets. I could get it fire if I shorted out the magnets. I thought about getting it repaired but it would cost double what I paid for a really nice (and working) body from ebay. So, if I ever need body parts, I have a body to salvage from. I have a feeling you might end up in the same position...

hamberger · Oct 5, 2016

flavio81 said:
Which is the exposure value that you get? Is it a very very dark exposure value?

Also, can you try turning off the camera, then pointing at the scene and then turning on the camera, so you can see the acquired exposure value. Is this exposure value appropriate for the scene?

I wouldn't fault the computer at all. If it was faulty you wouldn't get the LED readings.

On electronic cameras most such faults are down to silly things like bad solder joints (google "cold solder joint"), bad contacts. Light sensors, particularly the SPD sensors used on those cameras, are unlikely to fail by themselves.

It's actually a very bright value, at 400ASA it displays 1000 13

I tried a few different scenes, power cycling in between and even removing the battery, no luck as these values remained the same.

For kicks I adjusted the ASA to 200 and the reading changed to 1000 9.5 so it is calculating at least (staying positive!) I am glad to hear that the computer and SPD sensor are not likely to be the culprits

Looked up cold solder joints - so I guess I need to start taking it apart and inspecting all the connections, contacts, solder joints etc... a bit intimidating but I'll do some homework via these forums, the repair manual and YouTube

Wish me luck!!

hamberger · Oct 5, 2016

farmersteve said:
I bought an A-1 lens bundle off of ebay for the lens and was told the camera wasn't working so I only really paid the going price for the lens, the body was essentially free. I got it and the damn camera looked like the day it was made but the shutter wouldn't fire. I pulled the bottom off and tried fiddling with the magnets. I could get it fire if I shorted out the magnets. I thought about getting it repaired but it would cost double what I paid for a really nice (and working) body from ebay. So, if I ever need body parts, I have a body to salvage from. I have a feeling you might end up in the same position...

Optimism is powerful my friend!

I have high hopes to get this puppy metering beautifully

flavio81 · Oct 5, 2016

hamberger said:
It's actually a very bright value, at 400ASA it displays 1000 13

I tried a few different scenes, power cycling in between and even removing the battery, no luck as these values remained the same.

For kicks I adjusted the ASA to 200 and the reading changed to 1000 9.5 so it is calculating at least (staying positive!) I am glad to hear that the computer and SPD sensor are not likely to be the culprits

Looked up cold solder joints - so I guess I need to start taking it apart and inspecting all the connections, contacts, solder joints etc... a bit intimidating but I'll do some homework via these forums, the repair manual and YouTube

Wish me luck!!

That is the maximum EV value the meter allows (1000 @ almost f32 @ ISO 100). So somewhere the A/D (analog to digital) converter that gets the voltage from the metering system is getting a maximum value which MIGHT mean -perhaps- that there is a differential amplifier (that amplifies the SPD cell voltage) and one of its inputs has been disconnected, so the out of the amplifier goes to maximum voltage. And stays there.

Go get the A-1 service manual. It is out there on the web.

hamberger · Oct 5, 2016

flavio81 said:
That is the maximum EV value the meter allows (1000 @ almost f32 @ ISO 100). So somewhere the A/D (analog to digital) converter that gets the voltage from the metering system is getting a maximum value which MIGHT mean -perhaps- that there is a differential amplifier (that amplifies the SPD cell voltage) and one of its inputs has been disconnected, so the out of the amplifier goes to maximum voltage. And stays there.

Go get the A-1 service manual. It is out there on the web.

I ran with your idea - it makes perfect sense!

So I spent about an hour reading over the repair manual and I'll be honest, still not super confident with what I'm looking for even though I understand the concept of how it works. Here's what I've got. Does this appear to be the problem?

hamberger · Oct 5, 2016

hamberger said:
I ran with your idea - it makes perfect sense!

So I spent about an hour reading over the repair manual and I'll be honest, still not super confident with what I'm looking for even though I understand the concept of how it works. Here's what I've got. Does this appear to be the problem?

flavio81 · Oct 6, 2016

Sorry Hamberger, i'm not sure if i follow you. What do you see that appears a problem?

I'd suggest you to first take a deep look to the repair diagram circuit before doing anything. Sadly i don't have the spare time right now to do a look to the diagram. Give me more time.

farmersteve · Oct 6, 2016

hamberger said:
Optimism is powerful my friend!

I have high hopes to get this puppy metering beautifully

I know, believe me. I tried for a month to do everything I could eventually I just said to myself as long as these cameras are dirt cheap I need to stop and buy another body if I want.

hamberger · Oct 6, 2016

flavio81 said:
Sorry Hamberger, i'm not sure if i follow you. What do you see that appears a problem?

I'd suggest you to first take a deep look to the repair diagram circuit before doing anything. Sadly i don't have the spare time right now to do a look to the diagram. Give me more time.

IT'S ALIVE!!

It appears that this camera was previously [attempted to be?] repaired as that connection had burned solder.

I removed the old solder and had to do some adjustments to get the pins where I need them but after resoldering she started working!

You definitely pointed me in the right direction Flavio, thank you!

flavio81 · Oct 7, 2016

hamberger said:
IT'S ALIVE!!

It appears that this camera was previously [attempted to be?] repaired as that connection had burned solder.

I removed the old solder and had to do some adjustments to get the pins where I need them but after resoldering she started working!

You definitely pointed me in the right direction Flavio, thank you!

Another day, another happy Canoner.

OK; i'll bring out my Canon EF today for a walk, in celebration. (Canon EF being the spiritual 'father' of the A-1).

Enjoy the camera! I had a Canon A-1 and i LOVED that camera, actually shot some pics that made it into some Compact Disc albums with it. Then when the film era was apparently over, I switched to d!gital Nikon, and gave away the camera to my sister (she LOVED it and still has it).

Now i own the Canon F-1 New, the F-1 old, and the EF; but certainly i still miss my A-1. I think the best thing was the LED display, for some reason i find it really really comfortable on the eyes, the best display I've had on a camera. And you can turn it off, which doesn't seem like a great feature until you try it in real usage: Put the camera on P (program), turn off the display and have your brain focus 100% on the image itself, undistracted.

Final tip, if you did not read the manual: If you get a EEEEEE display, this is because the lens aperture ring was moved away from "A" and then the lens was stopped down. To resume normal operation, activate the double exposure lever, and then advance film.

Feel free to ask me for Canon FD lens recommendations, i've owned and own a lot of them.

flavio81 · Oct 7, 2016

PD: And fun thing is that "EV" are the two letters of my two last names, "AE" (as in Canon AE-1) my first name and last name combined, Flavio is my middle name, so "Canon EF" also has my initials, as well as "Nikon FE". And of course i proudly owned all those cameras.

CMoore · Oct 10, 2016

I have used my A-1 more than any other camera i own (at this point).
It is not the "best" camera for shooting in manual mode, but that is how i use it, and i think it meters beautifully.
And yeah...i dig the LED and the view finder on that model.
Granted, mine has been serviced, but all cameras of this age should be.
One of the best looking SLR that was ever made.
good luck

Reblochon · Apr 9, 2021

flavio81 said:
That is the maximum EV value the meter allows (1000 @ almost f32 @ ISO 100). So somewhere the A/D (analog to digital) converter that gets the voltage from the metering system is getting a maximum value which MIGHT mean -perhaps- that there is a differential amplifier (that amplifies the SPD cell voltage) and one of its inputs has been disconnected, so the out of the amplifier goes to maximum voltage. And stays there.

Go get the A-1 service manual. It is out there on the web.

Hi! Sorry for bringing this whole conversation up again, but I'm having a similar issue here. I was wondering if anyone could point me into the right direction.

I've got the same problem as Hamberger, but I suspect the metering system in my A-1 is getting minimum voltage. No matter what I do, the meter says that the scene is underexposed and recommends the highest aperture and the shutter speed is always bonkers. I just tried pointing at the sky on a brightly lit day but it's still recommending a shutter speed of 0.7s and an aperture of 1.4.

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