lens repair

In my recent trip to Asia I brought my Canon 7D DSLR together with a 17-85mm zoom lens. Very early into the journey the camera threw a fault code that it could not communicate with the lens. It suggested the electrical contacts may be dirty and needs cleaning. Knowing my camera and how I used it I knew the problem is not due to dirty contacts. Needless to say my spirit was dampened knowing I have to travel without my DSLR. Dreading the though of taking photos with my iPhones (I brought a old 3GS to used with prepaid SIM cards), I struggled to figure out a workaround.

As the camera was unable to take photos I figured if I just fool the camera as a dumb all manual lens is attached I should be able to continue use the lens, albeit without the ability to control the aperture. I found a piece of packing tape from a garbage bin to tape all the communication contacts. It was a bit tricky to ensure the tape does not slide off when I engage the lens to the camera with the bayonet mount.

The work around worked but taking photo is very painful and time consuming. The aperture is fixed at whenever the last energized state so sometime it was wide open, and another time was fulled closed (at the smallest opening). Because of these I had to use the ISO and shutter setting to compensate. While I considered buying a lens in Asia the prices there were much more than in the US. Also I would prefer to get a better lens second time around but being pressed on time I couldn't do the necessary research on the lens to buy. I ended up living with the crippled lens during the remainder of the trip, as well as using the iPhones. At the mean time I had done some research on the web and learnt that the likely cause of the fault is the aperture flex cable inside the lens.

Arriving home I order the alleged aperture. While most folks just order the flex cable on eBay for under $5 I decided to order the entire aperture assembly to avoid having have to solder the very delicate assembly. It cost a reasonable $35.

Knowing the repair is no cakewalk I was not looking forward to the repair. Among the brave souls who attempted the repair themselves some failed. I figured I've got nothing to loose I dived into the repair.
the bad boy lens - it is not the best lens but it is a great travel lens due to the wide zoom range and lighter weight

bayonet and lens dust cap removed

 2 of many tiny screws

the green thing inside is the printed circuit board that contains all the lens electronics which includes at least one microprocessor

 

 there is no going back now - i took only few pictures of the disassembling

almost fully disassembled - still having get to the alleged failed aperture assembly; you can see all the bits and pieces in this picture

 one have to completely disassemble the lens to get to the aperture assembly; it is still inside this plastic barrel in this photo

this is the failed aperture assembly - upon close inspection using a 10x eye loop I could barely see a pin hole that severed one of the miniature conductors in the flex cable

Assembling the pieces of the lens is very difficult as it is not easy to determine how all the pieces comes back together. It is also extremely easy to cause a irreversible damage. As it turned out after I assembled the lens it fails to function properly. I had to completely disassemble the lens and reassemble it back again after figuring out that I failed to slip one inside lens assembly lever into a guide channel. In all the repair took me about 6 hours. It was one of the most difficult repairs I'd ever done.

one of the test shots after the repair - everything works