Camera dead but drawing power

[Mark_M]

A post showing my findings.

I have two IP cameras which draw ~3w of power but do not show any network activity at all. No blinking network activity lights on a switch, or the device showing up on a managed network switch.
Same symptoms powering with POE or 12v DC.


What's wrong?
It appears the Ethernet cable was not the correct pin out. POE voltage was sent into the data lines.

Connected directly to the TX & RX lines of the Ethernet jack input is an S16503G LAN transformer. An isolation transformer.
Checkout the burnt pin on this camera. That's pin 14 TX- .



The LAN transformer has a bunch of little transformers inside. Something that could easily be burnt if too much voltage was applied, or maybe broken from impact in shipping. This photo shows one not potted in resin.


I bought these cameras used and have now received a refund since they were DOA.
The component costs $2 each off AliExpress. I'll buy some and report how it goes.


My message for Dahua Engineers: Please add circuit protection in case someone wires a network cable incorrectly and power is sent to the data lines.

 

[paul@austins.tv]

Very good diagnosis. Well done.
I've got some faulty IP cameras, I'll send them over to you?

 

[TonyR]

It appears the Ethernet cable was not the correct pin out. POE voltage was sent into the data lines.

Where did that Ethernet cable come from?

Power must have been supplied by a passive POE injector because I don't think a truly 802.3af/at-compliant PSE (POE injector or POE switch) would have supplied any power to the PD (the camera) if proper negotiations between them did not occur due to the miswired cable.

But I am by no means a POE guru.

 

[Revo2Maxx]

Don't know your Electrical Background but in the cameras that I have repaired and I have repaired a good many. With about 1/2 with dead Ethernet Transformers there was in most cases protection before and after the Ethernet Transformer. There is a good many reasons that these can fail. #1 issue for what I have seen people using CCA cables.. I mean sure I have some cheaper bullets without protection before but in truth the Ethernet transformer is one of the protection devices.. Things like Power Surge, Over Voltage, ESD, High Temps, Corrosion and or moisture. I mean sure they could do away with the need for the Transformer all together if they wanted. But would require many to wire the systems different by using all pairs of wires and not just 2 pairs. This they could use first pairs the ones that are right now going to the Transformer for data and the last 2 for power.. By the way the reason your camera is still powering up is because of the extra pairs.. So in some cases not all cases cameras can work in both Modes A and Modes B. But when setup for Mode A that is how it works. Yet when Mode A fails the camera can start working power in Mode B mode?

 

[Mark_M]

Where did that Ethernet cable come from?

I don't know.

This is the 2nd & 3rd camera I have bought used and had this issue. These two units were still in there boxes and had plastic on the front....
I've received a refund from the seller.

I think both units came from an electrician who put them aside for returns. The liquidator came through and listed them for sale.... for a sucker like me to find out they're damaged.
Hopefully it's just the isolation transformer to repair on both. The other unit has pin 9 (RX -) open circuit to pin 11 & 10.

 

[Mark_M]

By the way the reason your camera is still powering up is because of the extra pairs.. So in some cases not all cases cameras can work in both Modes A and Modes B. But when setup for Mode A that is how it works. Yet when Mode A fails the camera can start working power in Mode B mode?

I wouldn't have thought wiring as T568A & T568B could be a problem....? Because only green & orange TX & RX pairs are switched.
Brown & Blue for POE stay in the same location.
E.g, this image for a cross over cable (T568A to T568B).


The camera's are only wired for 100mb/s. TX & RX pairs come from the Ethernet jack, but blue and brown is down to a single wire each. Red & black is a single wire for the 12v jack.
Orange & Green are a direct connection to pins 1,2,3,6 on the Ethernet jack.

 

[Revo2Maxx]

Not sure related to one or the other 568A or B both work with POE as long as the ends are wired correctly. ModeB is Spare Pair power 45 positive and 78 negative mainly used in passive or midspan setup.

Also looking at your camera picture there looks like more damage then just the lan trans..

From what I can see it looks like the component next to the 2 caps by the green wire is also damaged?

 

[Revo2Maxx]

Looking at your picture looks burnt, in my picture of my camera looks normal. Seeing no markings for TVS I am guessing it's an inductor

 

[Revo2Maxx]

So looking at my power board opposite side of reset switch is same type component that is marked L1 and is infact an inductor choke designed to filter power from data

 

[Revo2Maxx]

Also wire mine as B off this diagram.. Strange so many different ways others wire things..

 

[Mark_M]

Also looking at your camera picture there looks like more damage then just the lan trans..
From what I can see it looks like the component next to the 2 caps by the green wire is also damaged?

Looking at your picture looks burnt, in my picture of my camera looks normal. Seeing no markings for TVS I am guessing it's an inductor

So looking at my power board opposite side of reset switch is same type component that is marked L1 and is infact an inductor choke designed to filter power from data

That black component with the dimple, I didn't notice that at 12am this morning when I was tearing it apart. Good spotting!
Multimeter reads continuity across it. Seems okay..... I'll order the LAN transformer component and hopefully that is the only issue.

My camera is also wired as T568B on the fly lead colors.
My comments earlier is if someone wired an Ethernet cable to the camera wrong and that power was sent down pins 1/2 or 3/6. Which would be incorrect wiring for T568B or A.

 

[Revo2Maxx]

1,2,3 and 6 is the correct wiring for POE and that transformer is what is there to pull the power out of the data on the center tap.. Here is a POE camera that has been depopulated, In the first picture you can see that this camera 1 2 3 and 6 go to the transformer, Then in the center of the pins at the transformer it goes to an inner layer and over to the Bridge Rectifier. I know it is on an inner layer because looking at the other picture you can see 45 and 78 going to the back side Bridge and no traces where the via comes through the board that is because they are running on inner layer of a mulit layer board.. Very Complex setup.. But anyway.. Transformer takes 1,2,3,6 and runs data and power - + to the transformer and pulls the power off the data passes that to the bridge before going into the rest of the circuit.. So looking at the first picture you can see the 1, 2,3 and 6 going to the Transformer area. There are 6 pads I removed the other 2 the center of other 2 pairs is where that Center Tap to pull the power out of the data lines happen though that transformer.. On the second picture you can see pins 45 are connected with trace and 78 are also connected then goes to the incoming pads of the Bridge.. Front Bridge is next to the ID5 area and that is where the inner traces come up as you can see next to ID5 are Via but on the second picture the via is there but no tracks because as I said before they are inner layer of the PCB..