How can I repair a Canon EF 200mm f/1.8L USM with failed focus-by-wire, and where can I find parts?
Asked 7/25/2013
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2 answers
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My Canon EF 200mm f/1.8L USM appears to use focus-by-wire for manual focus. On my lens, turning the focus ring has no effect, so I suspect a failure in the USM/focus system. What kind of precision tools are typically needed to disassemble a lens like this, and are replacement parts for this model still available anywhere?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
13y ago
2 Answers
6
The 200 f/1.8L is indeed focus-by-wire only.
Taking apart the lens is not a problem, but finding replacement parts is - they're no longer available from Canon and the Canon service centres are unlikely to have any in stock. I looked at buying a 200 f/1.8L with a broken AF system, the seller had found someone selling the replacement USM unit but even then I decided it too big a risk, if the fix didn't work the lens is next to useless as there's no way to focus it.
I suggest you trawl ebay for replacement USM units or donor lenses, contact the larger lens service centres to see if they have any inventory.
Originally by user1375. Source · Licensed CC BY-SA 4.0
user1375
13y ago
0
Generated from our catalog & community — verify before relying on it.
Yes—this lens uses focus-by-wire, so if the USM/focus system fails, the manual focus ring may do nothing.
For disassembly, you’d typically want precision repair tools like the kinds sold for jewelers or mobile-phone technicians: small screwdrivers, fine tweezers, spanners, and other delicate hand tools. Be aware that some lens repairs also require model-specific or improvised custom tools.
The bigger problem is parts. According to the community answers, Canon no longer supplies parts for the 200mm f/1.8L, and Canon service centers are unlikely to have stock. That makes repair risky: even if you open the lens successfully, sourcing the correct USM assembly may be difficult.
Your best options are to:
- search auction/used markets for a replacement USM unit
- look for a donor lens
- contact large independent lens service centers to ask whether they still have old inventory
Because this lens cannot be focused normally if the AF/USM system is dead, it’s wise to confirm parts availability before taking it apart.
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UniqueBot
AI13y ago
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