INSTRUCTIONS.
READ THE WHOLE PROCEDURE BEFORE YOU START. If you do not feel confident that you understand and can perform the procedure then do not start it.
Before you start ---- I will not accept responsibility if you break your LK-7900, you do this at your own risk! I repeat, if you try this you are doing it at your own risk... Dash cam talk forum and I are NOT liable if your LK-7900 does not work after you attempt this!
ALSO before you start to disassemble, check the camera works with your bench 12v supply and VGA connected to a monitor.. Lets start with a known working item!
1. Remove SD card and all cabling.
2. Put camera on work bench lens uppermost. mount block (GPS) at 12 oclock.
3. At six oclock (bottom ) find small 2mm notch in rim ( pic 1)
Insert a small thin flat blade into the slot and carefully start to lift the label upwards. Great care should be taken not to crease the thin plate.
Gradually work your way around the whole ring until it comes free. Lift it away and store. The reverse side is tacky with impact adhesive.
4. You will now see two holes at the bottom of the cam, previously covered by the plate. (pic 2)
5. With a small x-point screwdriver remove the two screws. With the cam lens upwards, lift the front plastic housing (containing the lens turret) away from the rear housing.
Do this gently and keep the lift straight. The only thing holding the two halves together are the plugs and sockets on the pcbs. When you split the housing, either the lens pcb or the larger circular pcb will come away from the rear pcb which is screwed in. (pic 3) The lens holder and ccd pcb is screwed to the inside of the lens turret.
6. Carefully remove the square of glass tape that is stuck onto the lens holder and heat sink.... You WILL need to use this again so remove it very carefully! pic 4 and pic 5
Put a mark on the heatsink and edge of pcb so as to know orientation when reassembling cam.
Unscrew the two x-point screws and very carefully lift the lens holder up and away from the heat sink.
There is NO need to remove the heat sink from the front housing.
7. With a fine pointed needle remove the glue between the lens holder and lens holder body, and free the holder so it can screw in and out freely. I had to wrap the lens holder in insulation tape and use a very small pipe wrench to break the stiction of the glue. Be VERY careful!! The HD cmos sensor is inside the assembly. Do not use solvents or heat to free the thread YOU WILL DESTROY THE CMOS SENSOR IF YOU DO.
(
IMPORTANT --- Do not remove the lens holder completely from the housing. It is keeping the cmos sensor from being ruined by dust and foreign matter falling onto it.
8. When the lens holder is rotates freely , then reassemble enough of the camera to test it. (pic6)
Temporary reassembly,
8.1 Gently press the loose circular pcb onto the fixed pcb, ( that is screwed to the rear housing), making sure the two mating halves of the inter pcb connector engage.
8.2 Gently press the lens holder sub assembly onto the circular pcb, making sure that the pcb connector is oriented the RIGHT WAY ROUND.
8.3 Be careful if you tilt the cam forward, the pcbs will fall off. Secure the pcbs with a strapping of insulation tape for safety.
8.4 Connect the VGA cable and the 12v supply. Insert your sd card into the camera. Do this gently otherwise you will push the pcbs off each other.
9.0 Now the acid test! Switch on and you should boot up and get a picture.
10.0 Set the focus to your hearts desire. Just gently screw the lens in and out until you get the sharpest focus at the distance you want the sharpest focus to be at.
Its very sensitive, about one half a turn to go from blurred to sharp to blurred again..
I used a camera target downloaded from the internet (pic 7)
10.1 When you have finished adjustments and tests, put a drop of glue on the lens thread and leave to dry.
11.0 Reassemble (the reverse of above.)
11 .1 Tear down test assembly
11.2 Put lens holder back in front housing IMPORTANT MAKE SURE IT IS THE CORRECT WAY ROUND SO THE TWO HALVES OF THE PCB CONNECTOR WILL MATE. If you marked it before disassembly it will be easier to replace correctly.
11.3 Screw in two screws to hold it in place.
11.4 Replace glass cloth square. MAKE SURE THAT IT DOES NOT OBSTRUCT THE PCB CONNECTOR.
11.5 Replace the round pcb onto the fixed round pcb.
11.6 Carefully offer the front housing to the rear housing ensuring the lens pcb connector mates correctly with the front round pcb connector.
11.7 Replace the two screws through the holes in the front housing
11.8 BEFORE replacing bezel on the front...... Apply power and TEST it is all connected and working correctly. ( The first time I got to here it failed because I had a strand of cloth across the ccd connector.)
11.9 Put the circular bezel in correct position and smooth down into place.
Finished!
Enjoy
P