Yesterday I have received my brand new YN565EX flash by Yongnuo from Hong Kong. It took almost a month for it to get to Estonia, but shipping was free.
The flash is very similar in specs to a much more expensive Canon 580EX II, with minor exceptions, e.g. no Hi-Speed sync or ETTL Master mode. However, the flash supports ETTL Slave mode of both Canon and Nikon systems, so this was the primary reason for buying it - use as a powerful (guide 58) slave flash unit in automatic TTL mode. As a bonus it can also be a slave in manual mode as well - overall a better option than buying a 430EX from Canon, which is even slightly more expensive, for the same purpose. The reviews on the net were very good and I was impressed with the build quality, which matches flashes made by Canon.
But all would be cool if it worked... There is much scepticism for buying of Chinese flashes, and there seem to be a reason for that. The flash powered on for the first time and then quickly shut down. It completely ignored any presses of the On button afterwards and soon I noticed that the batteries get very hot while they are inserted into the flash unit. Bad, bad, bad. My option would be to pay for return shipping and wait for 2 more months until the new unit is delivered. Not a sexy option.
So I decided to give it a try to fix it myself. Hot batteries suggested there should be a short circuit somewhere and if it is not a major component, it should be fixable.
The flash is very similar in design to Canon 580EX, so searching for its schematics helped to understand how to disassemble it.
Now the flash works perfectly both in the hotshoe and as a slave. There are no problems with balance of light with my Canon 580EX II - at least I haven't noticed any difference so far. The only minor problem that I have noticed is the modelling light (when depth-of-field button is pressed) gets darker by the end of the 1 sec interval it is supposed to be visible, but it may depend on how well the batteries are charged.
Overall, I am pretty happy now. Buy yourself one if you have basic disassembling/electronics skills to protect yourself from minor manufacturing defects. I really hope the QC will improve at Yongnuo.