Axis Q6034-E Speed Dome cam No Power

[Dannyx]

Good day folks. A friend of mine scored a couple of these Axis speed dome cams which no longer work and asked me to have a look at them, see if I can get it going. He also grabbed 2 POE injectors that used to power them. He said he tried both of them with a functional camera and they work, so the problem is most likely the cameras.

The problem: no power and no response from the cameras at all. The "activity" LED on the injector also blinks amber and according to the injector's manual, this means overload.

To cut the story as short as possible, I opened up one of the cameras and pulled the board from the bottom. The same behaviour occurs even with all other connectors unplugged, so I THINK the problem is on this board, though I haven't excluded the possibility of some further issues in the "head". Measuring with a multimeter, I DO see power spiking to 50v for a very brief moment in some places, including directly on the RJ45 connector itself, but this quickly drops out. I checked for shorts but there are none, at least not in any major components that I could immediately spot. So that's problem no.1: PoE doesn't start.

The next thing I tried was directly power the 4 small output caps of the POE section with 19v from my bench supply, which according to a thread I found here for a very similar camera, SHOULD've powered up the head, essentially simulating PoE working, but it didn't: in my case, the small fan on the head just spins briefly then nothing else happens, hence why I said there may be other issues with it. That discussion was never concluded sadly, so I don't know how/if the guy got it going...

There's 3 DC-DC converters on the POE output, easily identified by the 3 coils: when I feed 19v after the PoE part, two of them are fine and give me a 12v and 3.3v rail respectively, but the one in the middle is dead: no output at all ! Logic would suggest this should be 5v. The ICs running the 3.3v and the faulty (5v?) converter respectively are TPS5430. According to the datasheet, VIN is on pin 7, which it is - I get 19v there and there's also an enable signal on pin 5 and this is where it gets weird: no power on this pin whatsoever. I COULD NOT for the life of me figure out what this pin is connected to ! I spent like an hour measuring around with my meter trying to find ANYTHING connected to it, but couldn't ! It's not floating though. In fact, it's being "pulled to GND" by something, because if I measure the positive side of the CMOS battery with respect to this pin, I get 3v on it, so it's essentially GND, though not in a direct short or a low resistance there ! What I did was lift this pin off the solder pad to try and trick the IC into turning on, just to see if it works: it does, but there's no regulation at all ! Whatever voltage I feed into the "VIN" pin, also comes out the PH pin on the output, so that can't be good ! There's more: pin 4 is supposed to be a feedback network - there's no "high-side" resistor there ! The pads are unpopulated ! The resistor that IS there just goes to GND, so it's no surprise the voltage shoots up to whatever the input is. I did at some point remove the chip entirely to check resistances, but I'm fairly certain I didn't knock the resistor out of place by accident. I will check with the second camera to confirm, so there's problems no. 2 and 3: converter has no EN signal and doesn't regulate if forced on.

Now I'm not sure whether I should just replace the TPS IC (or try swapping it with the functional one). I sure hope whoever pitched in to help the guy in the other thread will do the same for me and maybe together we'll at least narrow it down...

[Dannyx]

Here's a close-up of the DC-DC converter in question, where the absent resistors make no sense at all....

[fzabkar]

You need to replace the feedback resistors. I suspect that someone removed them so that they could be measured out of circuit.

The datasheet tells you how to calculate their values:

https://www.ti.com/lit/ds/symlink/tps5430.pdf

Is there a uC which could be controlling the ENAble pin?

[Dannyx]

I'll look at the other camera to see if someone messed with those too. This one was missing all but one screw holding the board to the bottom of the "bowl", so it was definitely opened before, despite not showing any obvious signs of soldering (apart from maybe these resistors). Still, it doesn't explain why the thing's not starting, even with the missing resistors. Hopefully it didn't kill the head because it sent 19v into what's supposed to be like a 5v line. It's also strange that the output of this converter doesn't lead to any of the pins in the connector going to the head, but to the other one which leads to a sub-board which appears to run the fan and the heater, so I have no idea what's going on there or IF that board needs to be connected to send the enable signal. Again, couldn't trace that ENA pin anywhere....

Will check with the other camera first...

[fzabkar]

107E capacitors are rated for 25V. Wouldn't that be too high for a 5V supply? Are the fan and heater 12V devices?

[Dannyx]

One of the converters already gives me 12v, so unless it uses two separate 12v ones to do different things, I'm expecting the dead one to generate something other than 12v.

[SeanB]

Chip has been changed, looking at the massive blob of flux there, so likely the hot air reflow blew those resistors off, because for sure the poor tantalum capacitor there got really roasted. Likely chip is dead as well, just from running to 100% on time, and popping the internal switching device. Probably generates a 5V rail, to go with the 12V rail.

[Dannyx]

I already mentioned this briefly - it was me who removed it It showed no signs of previous rework (or they did a very good job hiding it !) so it could be that I was the one to knock the resistors off too, though I seriously doubt it, because I distinctly remember taking a picture and they weren't there. It doesn't change the fact the camera wasn't working prior to removing the chip myself. Will check with the other camera, hoping it hadn't been tampered with as well....

[Dannyx]

Ok, UPDATE: I just opened up the other camera today and this one also doesn't have the resistors ! It only has the one in the middle, the same as in my pictures - the other pads adjacent to it are unpopulated (so it wasn't because of me to begin with).

I also did the following experiment: I applied 12v to the coil that normally produces it and measured pin 4 of the IC and I get 1.2v there, which is what the datasheet says it should be when the desired output voltage is reached. Of course, this only happens to the functional converter (the 12v one)- the "dead" one with the mystery resistors, which I assumed is 5v doesn't give me anything and I was afraid to go higher than 5v. Another theory would be that it somehow loops back through either the head OR the base - there's another ribbon which connects a sub-board attached to the "bowl". I didn't think twice about it because it appears it only powers the heater and fan, but it seems awfully complex for just this, so maybe it's somehow involved.....

[Dannyx]

I did some more experimenting and here's what I found: the camera head works just fine. I just needed to wait a little longer after applying 19v externally like I previously mentioned and the orange light came on. At first it looked like it wasn't doing anything, yet it was still drawing 2A somehow. Turns out it was the heater attached to that sub-board mounted to the bell. However, disconnecting that board entirely has no effect and the head runs just fine, at least with PoE bypassed like this.

I also decided to finally open up the injector as well, mostly out of curiosity and here's what's inside: the plastic connector from the power supply to the PoE module (let's call it) is baked to a crisp - it completely disintegrated when I touched it - yet power still flows through. According to the writing on the PoE board, which you can't quite see in the pictures, the 3 wires are "VMAIN", "GND" and "12v". VMAIN is a constant 55v, GND is GND and 12v is.....8v...OK...this doesn't seem right to me. To confirm I tried supplying 12v from my bench power supply, while leaving the 55v terminal connected, but the same thing happens: the "port" LED goes from yellow to green very briefly, then back to yellow and no power comes through at the camera end (still jumps between 50v and 0) so the problem is on the camera board still. I'm starting to consider replacing the two ICs.....

[Dannyx]

OK guys, update: I replaced both ICs and the camera is working, so that's the solution - bad PoE ICs Time to do the other ones now and see how long they last