2CD2042WD-I PCB repair

[gmo78]

After a fault on my gutters, the junction box of my 2cd2042 (powered by poe) was submerged by water and the cam stopped to work. Using the cam with a 12v power it works, so I supposed the POE pcb has one or more burned fuses.
I dismounted the cam and checked the pcb, but I didn't recognize any burned components.
The connection between the lan plugs and the connector inside has no faults (checked with a tester).
Can somebody help me to recognize the broken fuses?
Regards
Gian Marco

 

[alastairstevenson]

Can somebody help me to recognize the broken fuses?

It's not likely to be a blown fuse - however, I think the fuse will be under the barcode label on the top side next to the ethernet transformer.
Look for the component that has the label 'CQT 1.5A'

When you checked the RJ45 socket to the internal plug, did you also check for shorts to any other pins as well as opens?
With water ingression and electrolytic corrosion you could get both.

 

[gmo78]

Thanks for the answer.
I found a component with the label SH 1.5A just over the transformer (in my photo, this component is in the shadow of the transformer) but, unfortunately, the tester shows 0 ohm.
I did not check the shorts, you right. My tester beeps with the pins white orange and orange, white-green and green, blue and white-blue. This looks like a bit strange to me, because the cam is actually running with an external 12V power supply and the lan cable of a not poe plug of my access point.
The best, probably, should be to find a new pcb...

 

[alastairstevenson]

The best, probably, should be to find a new pcb...

I don't quite follow how you have tested the cable.
Suggestion:
With the plug on the cable end inside the camera unplugged.
With the RJ45 cable outside the camera unplugged.

One multimeter probe on the first pin of the plug.
The other probe connecting to each of the pins of the RJ45 plug in turn should show one beep on only one pin.
Repeat with the probe on the next pin of the plug until all done.

A beep on 2 pins would be a short, and may be the cause of the problem.

 

[gmo78]

Well I explain better what I checked.
- First test, the internal molex connected, the external female rj45 connected to a lan patch for make the check easier. The result is as written before: beeps with white orange and orange, white-green and green, blue and white-blue (white orange is tx+, orange tx-, white-green is RX+, green is RX-, blue and white-blue are poe power positive).
- Second test, the internal molex disconnected, the external female rj45 connected to a lan patch for make the check of the cable easier (as in the photo). Well no shorts between the pins, and no interruption between the same wire, the internal cable is OK.
The second photo is again the PCB of poe, with the components under the lable and a view of SH 1.5A that is not blown.
Do you think I can power the camera with poe and test the transformer?

 

[alastairstevenson]

Well no shorts between the pins, and no interruption between the same wire, the internal cable is OK.

That's good, that's the way to do it.
With the internal connector in place, the ethernet transformer will show connections between 2 pairs of wires, as you found, maybe hiding some actual shorts.

Do you think I can power the camera with poe and test the transformer?

I think fault-finding down to the component level would be tricky, and need more than a multimeter.
I'm thinking that via the ethernet cable itself, there is not much that you can do to damage the POE convertor with water ingression.
Even reversing the polarity would have no effect, and there is no over-voltage.
But what is possible is the 12V DC jack being exposed to part of a stray 48V source, which could reach back into some of the internal POE circuitry that feeds into the 12V and do some harm.
But check the protection and overvoltage diodes for shorts - the big square devices with 2 pins, and also the POE bulk capacitor, the smaller one near the cable connector.

As it still works with 12V, and you'd like to keep the use of it, maybe a simple solution would be an active POE splitter at the camera end, if you can fit that in the space.

 

[gmo78]

I tried also the Schottkys as your suggestion and they looks like to be in the specifications (infinite ohm on one way and about 300 ohm on the other way).
However I powered the pcb with a normal power from poe. Well on the left pins of the transformer I can read 48VDC while on the right pins no voltage at all. So I would say the transformer is gone. The code on it is 30a60 1735f, but I can't find informations on google.
Please note the led inside is on.

 

[alastairstevenson]

Well on the left pins of the transformer I can read 48VDC while on the right pins no voltage at all.

Not necessarily so.
The POE side of the power supply is completely isolated from the lower voltage side.
Did you use a GND from the low voltage side to measure the other side of the transformer?
With the LED showing - I think that's off the 5.1V supply - it suggests the main part of the POE convertor is working.
There are multiple power convertors fed from the 12V DC that the POE convertor and also the 12V DC from the jack provides.
Any one of these not working would cause a 'dead' camera.
Without looking in detail at the images - are there any test points showing for 5.1V, 3.3V and 1.2V ?

 

[gmo78]

I have noted it is isolated, so I checked all the combinations between the pins (es. 1 with 2, 1 with 3 etc.).
Anyway, after all this assembly and reassembly of the connectors, the camera suddenly started to work (heard the sound of the relè). Looks like a fault on the flat cable, I can think... I still don't know how because the inside of the camera was completely dry.
I will observe the camera for a couple of days and then I would consider the issue solved.
Thanks alastairstevenson for your time.

 

[alastairstevenson]

Wow! That's amazing. And a little odd, in the sense that it worked on 12v but not POE.
Usually if the ribbon cable to the sensor was disconnected, the camera would be in a fairly long bootloop.
But all's well that ends well.

 

[gmo78]

At the moment it is working with POE.