I ordered and received an LK-7700 (ebay, Greensum, $130). It took all of 4 days to arrive, very impressively fast shipping. Its focus is very acceptable even if not perfect.
So, I finally got around to disassembly of my LK-7500 which had horrible focus - a spot on the windshield a few inches from the lens was in perfect focus but everything at normal distance was very soft. I bought it on ebay from a seller who promptly disappeared, and Chrontech (sp?) wouldn't help, after many sample stills / videos to them they said it was 'within tolerance'. It was really quite unusable.
Disassembly was quite easy, easier than the 7900 early in the thread.
- unscrew and remove the mount / GPS module.
- remove 2 phillips screws from the rear.
- unsnap / remove the rear cover
- remove the 2 side buttons and the slide power switch so they don't get lost.
- remove 2 phillips screws holding the PCB, pry up and remove the PCB.
- remove 2 phillips screws holding down the lens / sensor assembly from front cover, remove assembly.
- do what you have to do to loosen the lens. In my case, scraped a bit of the locking compound loose from the threads that I could see, secured the rectangular sensor base in an 18mm open end wrench. Wrapped electrical tape around the lens. Used a pliers to break loose the lens threads - it was tight! But after that, the lens could be screwed in or out by finger pressure.
Focusing - used a small 12v battery with a female cig lighter adapter hooked to it for power. Used the AV cable that came with my 7700 to hook to a TV in the kitchen. Keep in mind it is a VGA interface, so resolution is not great, but good enough for focusing. I had marked the lens position using a fine scratch mark before loosening, so I returned it to original just to check. Using a business card to focus on, I moved it about and sure enough, it focused at 3-4 inches - way too close, and anything beyond 6 feet was out of focus. I turned the lens and focused on a chair about 8 feet away. Took everything out in the back yard, moved the camera around and found that everything from about 4 feet to infinity looked to be in good focus. Put in the SD card and recorded a minute moving the camera around as a double check. Looked good. Put a tiny drop of purple (low strength) locktite on the threads.
- reassembled.
The LK-7500 is now in great focus. I can now read signs, plates, etc. I should have done it sooner rather than wasting time trying to get someone else (like the manufacturer) to fix or replace it. The internal design and build quality is impressively good.
Now that the 7500 works like it should, I did a careful comparison between it and the new 7700, and guess what - the 7700 is slightly out of focus, again focused too close. Not nearly as bad as the 7500 was, and totally usable, just not perfect. Thanks for the help provided by the previous folk in this thread for their help and encouragement.