As a Canon 300D owner I recently fell foul to the common problem of a failure of the autofocus system. The lens would rotate fully in either direction but never to a point of focus. I did some searching and discovered that it was a problem with the secondary mirror underneath the main mirror that is used in the auto focus system.The story continued, when after a bit of examination, I discovered that the sub mirror was jammed up under the main mirror and that was the cause of the auto focus failure. The tiny spring holding the two had become dislodged and yet held the two together. When I removed the spring in order to refit it I found what is commonly known as the “half black problem”. This occurs when the sub mirror isn’t lifted fully by the main mirror when the shutter is released and obscures the sensor.
I managed to refit the spring using a technique I found on the web.
However this was only part of the story. The mirror assembly hinges on a small plastic pin and combined with the spring allows the sub mirror to rotate and move up to join the main mirror during shutter release. This pin had broken.
Whether or not Canon accept this as a problem is not my concern. After 4 years and over 10,000 shots wear and tear was bound to creep in. I suppose Canon would put it down to economic reasons. Firstly they can charge to fix your old camera, or secondly you would feel the time was right to upgrade to a new model, which after investing in lenses, wouldn’t be a Nikon…
The broken pin is fixable by someone with patience and care and the right tools. There are many blog posts and articles detailing the fix and I am not going to repeat them in full but I want to add my experience to the procedure in order to help prevent the situation I now find myself in.
The two main articles I used in my repair were by Jan-Erik Skata and Tobbe Arnesson both of which are fantastic but Tobbe Arnesson’s page shows a more step by step approach, which suited me, as I was a bit wary at first.
I also made reference to the 300D service manual which can be found here.
Using the guide I managed to insert a new ‘pin’ in the shape of a paper clip and complete the repair of the mirror assembly. Before putting the camera back together I was able to confirm that the sub mirror rotated correctly around the pin and draw up under the main mirror.
Tobbe Arnesson’s page mentions the difficulty in getting the flash assembly free of the main chassis and I can confirm that it is difficult and also that the warnings of high voltages are true!
What Michael J Dixon notes, however, is that it is possible to diffuse the current in the large capacitor, thereby making the flash board safe and easier to grip and remove without fear of shock. He suggests using a 5kOhm resistor over the discharge points to remove the charge. I only had a 2k2 Ohm resistor so used that, which also worked. I found the discharge points in the service manual detailed above.
Once the capacitor is discharged, removing the board may be easier but still care needs to be taken of the delicate orange ribbon cable that the board is attached to near the legs of the smaller capacitor.
The orange ribbon bends up and away to inside the chassis and does not tolerate a lot of movement – as I found to my cost.
The above shot shows a tiny tear in the ribbon cable that occurred either when removing or replacing the flash board. The effect of this is that neither the flash, nor the metering system will work. You can still take shots but you have to meter yourself, using a best guess approach and bracketing adjustments – not ideal!!
The tear in the ribbon is tiny, only a couple of mm across but the ribbon is double sided – there are connections running through both top and bottom of the cable, so repair is impossible. Also I doubt it would be very easy to remove the ribbon and replace with another as there are many solder points and connections further around the camera.
So all in all, I’m glad I was able to find such help around the internet community but I’m annoyed with myself that I was unable to complete the repair successfully. Hopefully these notes will aid others in their quest!
Or just hand over your precious camera to Canon service and bite the bullet.
As for me… when does the 450D / XSi hit the shops??