20D - Manual Mode: I can't adjust the Aperture - Why?

Tim,

I think I will take it to the shop. Samy's Camera, where I am, are great people and they'll be able to help, I'm sure.

Mark,

Thanks for your help too. All custom functions are at "0" and the contacts on both the lens and camera look OK. The lens works fine in all other modes, it's just this manual mode exposure thing and i've tried at least two lenses on the camera to check it.

Thanks all for the advice, if you come up with any other ideas let me know. I will post the results when I get some feedback from the shop early in the week.

--gmaize

Good luck!

In one respect, I am sorry that we didn't come up with an easy solution.

On the other hand, a really weird problem like this is good for stirring up the brain matter.

If the rear dial works for some functions, then it should work for all, because it is a stupid switch that doesn't know any better. As long as the main switch is set beyond On to allow the rear switch to work, then it ought to work.

---Bob Gross---

Since the rear wheel appears capable of adjusting some functions it doesn't sound as if the wheel or switch to activate it are faulty. Possibly you could try removing both the main battery and the button cell, leave them out for a short period, reinstall them, and see if a "reboot" of the camera restores the functions.
I don't know if you had mentioned if the camera had always had this problem or did it just recently occur.

Mark........

I've just checked on my 20D and all the settings you say can be adjusted I can also adjust with the rear dial turned off (switch just in on position) - but I still need to go to the 3rd position to adjust exp comp. or av in manual.

This goes back to suggesting you have a faulty switch

Mark,

Interesting thought about the battery. What do you mean by the "button cell" By this do you mean the small date/time battery. Other than losing the date and time, is there a downside to removing this batttery.

The problem I have been describing is not a recent occurence. I did notice the problem within the initial month of ownership, but I do remember it going away and reoccuring periodically. I've had the camera since December of 2004 and would say it has been used lightly, certainly less than 5000 photos. I don't shoot manual mode much, but yesterday I really could have used it. This is when I noticed the problem again and decided to try and ferret out the issues.

If taking out both batteries has no other ramifications (please advise) I will try this and respond.

Much thanks!!

--gmaize

The button cell is the battery that holds up the memory while the camera is switched off. As well as time and date, it holds all of your personalized settings that you have done since the camera was new. For instance, custom function settings, owner name, etc.

I don't think that anybody is aware of any specific custom function setting that would account for this rear dial issue, but since other custom functions control the function of some of the other control switches, it can't hurt much (other than dumping time and date, owner name, and your other custom function settings).

---Bob Gross---

Bob,

Thanks for clarifying the function of the button cell battery. I took both the main and button cell batteries out of the camera for 15 minutes. Re-installed and no change with my problem.

But......I KNOW FOR CERTAIN NOW THAT IT IS THE POWER SWITCH. I was able to get the exposure changed in manual mode, but only after applying pressure to the power switch with my left thumb, while turning the big wheel with my right thumb. I had to apply just the right amount of pressure on the power switch to get the big wheel to function and then when I released the pressure on the power switch, the big wheel stopped functioning.

THANKS TO ALL FOR HELPING ME WORK THROUGH OPTIONS TO FIND THE REAL PROBLEM HERE. I CAN NOW GET ON WITH MY DAY....HAHA.

I'm off to the shop on Monday...

--gmaize

Hello all,

THE PROBLEM HAS BEEN SOLVED....MERCIFULLY!!

I just picked up the camera from the Canon Service Center in Irvine after 5 days in the shop (1/2 of what they quoted). It was indeed the power switch causing the problem. The service report stated that they cleaned and reconnected the FPC. They explained that it was a loose wire....presumably on the back/inside of the switch.

And just for kicks they cleaned, lubed and aligned the CMOS sensor, focus, shutter and mirror. All checked out OK.

Mostly I just wanted to thank you all (Tim and Bob Gross, especially) for taking the time to discuss this with me, when I was at my wits end. I respect you guys more everyday. Now I can work in manual mode where I belong. You guys are always pushing us to get out of program modes and go manual.

Best regards,

--gmaize

No problem, glad it's working for you You don't need to work in manual (M), I don't much unless i'm using a flash, usually i'm in Av, I mainly need the wheel for EC.

Glad to hear your cameras fixed and also to hear what the fix was. It would almost be good to have a Sticky that listed various problems and the resulting fix as a guide for others to aid in troubleshooting problems.
You didn't mention, but was your camera under warranty for the fix and if not was Canons charge in your opinion reasonable? You're at least fortunate to be close enough to be able to drop it off rather than ship it.
Mark........

Mark,

I am indeed fortunate. I drive by the Canon Irvine building everyday to and from work. When I walked in they didn't even ask for any proof of purchase or anything. They said not to worry since the 20D has not even been out for a year, there was absolutely no question, it was under warranty. Since I had registered the Camera Online with Canon they just looked up the serial number, completed the paperwork and I was off. No charges for any of the fixes or the cleanings. This is first rate in my book.

2010 update

It is a fairly easy repair, On mine it was buildup green-gray matter on the switch contact. (like on old batteries)

I had to dismantle the switch and use vinegar on the contact.

Here is how to remove the screws. http://simulated.ca …-20d_shutter_replacemen​t/

(stop at pic 5-6)

Attached are pics of the contacts, clean vs ugly.

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Why is there a shiny three legged lizard inside your camera?!