Lorex Security Camera Problem

[yugu]

I bought a Lorex Home Surveillance system with 8 cameras 1 year ago. And now 3 of them do not work properly. Before I throw them away, I would like to ask if there is any easy fix or not. Here are the symptoms: When pointing to something very bright, that part of the image became very noisy and purple-ish, as shown in picture 1. The second picture shows the part number of the cameras.

Another interesting thing is, all the 3 bad cameras are in front of my house, which is facing south. So I guess it must has something to do with the strong sun light. (The camera themselves are under shelter. But they are monitoring places under direct sunlight)

Does anyone know what's wrong with the cameras? Thanks a lot! ;-)

[Fraser]

Do these cameras have lenses with integrated IRIS's ?

Wit the scene you have provided I would have expected the camera to have shut the image right down to cope with the bright light coming through the window. Mechanical (galvanometer driven) IRIS's can get sticky and so stay open or closed. If it stick fully open, the camera may try to compensate bia its electronic shutter but when overloaded all manner of odd effects occur.

Aurora

[Fraser]

Just saw an auction for these camera models.

http://www.ebay.com/itm/NEW-Lorex-Camera-Security-MC7711-Color-Day-amp-BW-Night-IR-BNC-Cable-700TVL-AIS-/141158694413?nma=true&si=igOQ4x6Auz6yGDDqoMqiwWAHKig%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

They have a moving IR cut filter that should be in the light path during the day. If not, you will get weird colour effects due to UV content. They also have an "Anti-Glare feature to cope with all lighting conditions.....maybe that is an IRIS or some electronic shutter technique.

Have you tested any of the other cameras that appear to be OK ? Place them in teh same position as a suspect camera and compare results.

P.S. You should be able to hear the IR cut filter switching in and out of the light path as you cover the front of the camera (activating low light night mode) You can also often see it by looking down the lens towards the imager chip.

Aurora

[yugu]

Thanks Aurora. I opened one up, and there is an automatic mechanical switch there. If I cover the camera with my hand, the switch clicked it (pic 1). If I remove my hand, the switch popped out (pic 2). Two observations:

+ When the switch is in, the camera enters night vision (black&white) mode. In this mode, there is no purple color issue. However, the noise in the bright area does not go away.

+ If I manually push the switch in, it does not turn the camera into night vision mode. And there is no noticeable change in the color/quality of the video.

I am planning to disassemble it further. Please let me know if there is any other test that could help. Thanks!

Have you tested any of the other cameras that appear to be OK ? Place them in teh same position as a suspect camera and compare results.

The other cameras are ok.

[yugu]

Just verified that the IR cut filter is switching properly. The problem should be in the electrical part.

[yugu]

Here are the pictures of the PCB. For those who are interested. 

[SeanB]

Bright area is a burn on the image sensor. No way to repair, it happens because sunlight is focussed onto that small spot, and burns it, or overheats that small section till it starts to degrade rapidly. Very common on security system cameras that do not move, and which face the sun or a bright reflection for a good part of the day. As the sensor is likely less than a 1/4in on a side the energy focussed on it is rather high.

[yugu]

Thanks SeanB for your input!

So I probed around a bit and tried to see if there was any bad peripheral component. So far I didn't find any but made an interesting discovery. Once I shorted the input and output of the voltage regulator next to the motor driver, everything became normal again. It even worked after I removed the short. I tried several times (power off, turn on, short and then remove the short) and it was indeed reproducible. I measured the voltages of the voltage regulator's pins before and after the temporary short. They didn't change at all! (The output was temporarily raised to 3.9v from 3.3v during the short.)

What could be worse than throwing them away? 3.9v is not much higher than 3.3v, isn't it? ;-D So I went ahead and shorted them permanently for two bad cameras. So far they have been working normally for more than 15 hours. (I will keep monitoring them for a few days.)

This is still a mystery to me. There's another regulator with the same model number on the PCB and the ouput is the same 3.3v. So I believe it's not malfunctioning. I didn't find any other bad components, either. Maybe the CCD is lazy and needs a gentle push to work? lol

If you has any theories about it, please do let me know. Really appreciate it.

Cheers

[SL4P]

You were doing so well until you said "gentle push" !

I'd be looking a the PSU primary side for bad caps etc, as I'd guess the 3V3 is correct, but the regulator is expecting more than 3V9 at the input. 
Or perhaps overheating in direct sunlight has 'warmed up' some other parts?

Did you look at the 3V3 with a scope or meter?  Maybe the regulator is pumping to present a weak 3V3...
More exploring, but it seems harsh to throw them out or shorten the life with overvoltage - if they do work under 'certain' conditions.

[yugu]

Haha thanks. "lazy" is a better word, I admit.

I did check the output with a scope and the voltage was very stable. I tried injecting 5v to the input but it didn't fix the problem.  I also tried zapping the output with the following voltages

+ 3.5v or 3.75v, doesn't work
+ 3.85v, work!

So, as long as I zapped the output with 3.85+ volts, the camera would return to normal.

Please note that the camera continue to work normally when the output dropped back down to 3.3v after the zap.