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Old 01-06-2022, 02:03 PM   #1
Dannyx
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Red face Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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 short, I opened up one of the cameras and extracted the board from the bottom. The same behaviour occurs even with all other connectors unplugged, so I THINK the problem is the POE part on this board. 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 found none, at least not in "big" components.

Sadly, it's also here I realised I have no idea how POE actually works and proceeded to doing some research, but came pretty stuck because it quickly went a bit over my head. I was able to identify two "building-block" DC-DC converters on the board there (large caps+"coilcraft" coils), but these too have no power on the output - just those bursts of 50v on those big input caps. If you're wondering, yes, out of curiosity, I pulled out one of the original caps, but it read perfectly fine on my ESR meter, even after all these years, yet I tried replacing it to see if it makes the least bit of difference - it didn't, so I didn't bother replacing the other one too until I figure out how it actually WORKS, which is the main point of this discussion really !

From the RJ45 connector, I can clearly see 4 traces going to that black "poe+ETH" box thing, which I presume is a transformer like on all NICs/laptops, whatever. From there, the 2 pairs continue to the connector that goes to the moving head, so I assume those are for data and that's where the actual "NIC" of this thing is in the head - not down here on this board. What about power then ? It's not very clear on the photos I've taken, but I see 2 pins directly shorted together (the first ones, depending on your orientation). I assume they are pins 7-8, so I'm expecting 4-5 to ALSO be shorted together, just not visible from underneath (forgot if I actually measured this).

The two ICs that seem to run the whole show are those NCP1081. All the application schematics there show pins 4-5 and 7-8 shorted together, which would confirm what I found above. I doubt this camera uses Gigabit Ethernet, so it leaves the 2 "data" pairs alone (green and orange) and directly shorts the remaining 2 (blue and brown) to carry power.....ALTHOUGH, it could be the black box has center taps on those data lines, so those TOO could "extract" power from the data pins themselves, just so the camera is compatible with both A and B standards, which I read is a requirement (???) There's probably something signaling the injector to stop, not necessarily a short....again, I'm not entirely sure what conditions must be met for it to keep supplying power, besides the transmission itself...Any ideas what I should check ? Should I just replace the NCP chips or try a different injector, despite the guy claiming both of these work ???

The injectors output 55v (label says so), so I was hesitant to connect them to a known good 48v Hikvision camera to it to see if that "port" LED behaves differently or if it's unable to sustain the load and the problem has been on the injector side and not the camera side this whole time !
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Old 01-06-2022, 10:44 PM   #2
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Check resistance to ground on all of the buck/boost circuits. I see 3 inductors that are possibly used for power conversion (not counting the Coilcraft ones or the POE+ETH one.) If any of these inductors show a very low resistance to ground, chances are the main IC(s) may have been hit by a lightning or other similar surge. Also check the associated MOSFETs and diodes on those power rails for short-circuit. If the POE injector is indeed shutting down and indicating a power overload, then very likely that is what's happening - something, somewhere, is shorted on a DC power rail.
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Old 01-07-2022, 09:54 AM   #3
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Thumbs up Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

I think I already checked all major components and didn't find anything bad, hence why I started this whole thread, just in case someone spots something or knows from former experience a common cause of failure in PoE circuits. It could be I missed something indeed, or the problem is buried somewhere pretty deep.

I don't have the board on hand, but I'll start checking again from the RJ45 jack and work my way inwards. I'll even try something more extreme: provide my own power after the buck converter to see if the camera does anything, just to rule it out. The 4 small output caps of those 2 converters are rated at 25v and although this is a pretty big PTZ camera which would make sense to run on something like 24v, I'm not sure they'd design it that close to the rating of those caps, so maybe the output is 12v or thereabouts - best to start off small. This will also allow me to monitor current in case something else downstream fails only when powered up and measures fine when "cold"...
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Old 01-09-2022, 12:27 PM   #4
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Quote:
Originally Posted by Dannyx View Post
I think I already checked all major components and didn't find anything bad, hence why I started this whole thread, just in case someone spots something or knows from former experience a common cause of failure in PoE circuits.
Well, I don't know much about PoE circuits at all (probably less than you)... but from a power supply perspective, it looks like there are at least several buck/boost converters in there. If their MOSFETs and diodes are OK, just check resistance to ground on the output of each of these rails (so check resistance between ground and one end of each inductor - the "563F", "393j", and "183d" inductors, in particular.) If any are shorted or have a low resistance, that could be why your PoE injector is showing overload, as the buck circuit that converts the higher voltage over Ethernet struggles to "feed" whatever is downstream from it in the camera, due to one of these converters trying to feed possibly a bad IC or shorted ceramic cap.

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I'll even try something more extreme: provide my own power after the buck converter to see if the camera does anything, just to rule it out. The 4 small output caps of those 2 converters are rated at 25v and although this is a pretty big PTZ camera which would make sense to run on something like 24v, I'm not sure they'd design it that close to the rating of those caps, so maybe the output is 12v or thereabouts - best to start off small. This will also allow me to monitor current in case something else downstream fails only when powered up and measures fine when "cold"...
Yes, that's another way to go about it... though I still recommend checking the resistances first so you don't end up wasting time trying to feed power into the circuit and then trying to figure out where it's going or what's shorting it (if anything.)
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Old 01-14-2022, 03:06 PM   #5
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Talking Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Today I tried powering the board after the caps as previously planned. By accident, I came across a post on EEVBlog where a chap was having an almost identical issue with an almost identical camera. His symptoms were exactly the same, so I was REALLY curious if he managed to get it going, but sadly the thread died half-way through and it was never solved. I replied anyway just to see if there will be a follow-up, but I doubt it.

However, I did get one interesting piece of info out of it: the guy had the same idea and powered the camera after the PoE part by applying power directly to the output caps. He said he tried 19v and the camera started, so I did the same. I wasn't as lucky though: mine does nothing....well, almost nothing: the tiny fan on the dome itself spins briefly then stops....that's it. Sh!t - I was afraid I may have more problems in the head itself, but I decided to stay calm and not throw in the towel just yet. See, it could be one of the downstream converters IS indeed faulty, despite having no shorts that I could find outright, which tells me something must be failing when powered, like an IC getting "stuck on", but ONLY when power is applied. I decided it's time to reverse-engineer this thing a bit and focus on the rest of the board, not just on the PoE section, as much as I hoped I wouldn't have to, because it's multi-layer, so it's not fun to work with...

I wanted to see how "VIN" (B+ so to say) actually goes INTO the converters, but I wasn't getting a direct connection between the positive leg of those small output caps and the input pins of the ICs (there's 3 switching converters, so 3 ICs, 1 of which is different to the rest - THIS one, an LM5576).

Turns out VIN must first go through a transistor before getting to the converters: it's this SOT23 transistor near this large "152" resistor in the picture. It's labeled 610ZT and I couldn't find anything about this part right away. Google however, based on my search, somehow DID stumble upon an Ali listing for a part that looks identical, so I looked up the datasheet for that one and although it could very well be a different part entirely, the pinout seems to match: you've got the Gate pin where the small black resistor is, 4 Drain pins to the right (2 on both sides, which act as the "output" ) and 1 Source pin (bottom left from "R010" current sense resistor there, which acts as the "input").

There's also the current sense resistor and that LTCWK part: the LTCWK is THISso if my theory is correct, VIN arrives through the CS resistor, through the transistor's S and finally out through D to the 3 converters. Since there's a fault somewhere after the resistor, the LTCWK IC detects overcurrent and shuts off the transistor, hence why the fan briefly spins then stops and I get no boot. The next step is to:

A) gently inject power from my bench supply even deeper into the board. In fact, directly into those 2 solder joints in the picture which by the way correspond to GND and VIN AFTER the transistor, connected to the D pins, so the "output" of the transistor so to say.

B) check to see what/IF the 3 converters output anything (provided I can sustain power) or what goes pop if I start pumping some amps there. This being after the CS resistor, LTCWK has no way of stopping that now and I can at least blow up what's at fault I think I'm getting close to cracking it
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Old 01-09-2022, 11:33 AM   #6
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

My first go to would be caps, buck converters and magnetics. Could be also the main IC’s being bad. I’d look at spec sheets, then measure voltages and keep isolating the problem. Maybe it’s just a bad SMD cap… who knows.
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Old 01-09-2022, 11:52 AM   #7
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Probably "magnetics" as you put it, though I'm not sure I can remove the magic black box to check it - it's SMD and heating it would probably destroy what's inside. Even after the fact, I'd be using my meter to take a DC reading, so it would read as a short if I'm not mistaken....
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Old 01-26-2022, 06:58 AM   #8
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Talking Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Ok, another update, since I opened up a thread over on EEV and have been mostly updating that one, so I figured it's only fair I should keep up with this one too

Turns out the camera DOES work - I just had to wait a little longer after supplying 19v after the PoE part. Eventually the amber light came on...duuh

I decided to just skip ahead to replacing the 2 NCP1081 ICs and hope for the best, because there's clearly nothing wrong downstream. I'm waiting for the chips to arrive, so in the meantime I did another experiment: I cracked open the PoE injector and was presented with a lovely power supply with 2 rails, one of which supplies the actual 55v to the PD. I ran two alligator clips from the supply to the camera's board where 55v SHOULD show up (the two big input caps) and nothing happened (aside from the obvious big ol' spark !): I couldn't get a good measurement and didn't feel like playing around with 55v too much, but I THINK I recall not getting anything out of the VDDH and VDDL pins of the chip (nevermind the DC-DC output). One thing I DEFINITELY did was pop the gate resistor of one of the FETs after my probe slipped and I sent 55v directly into it The FET seems to have survived - just the resistor popped...

According to the datasheet, these should get generated when the chip starts up......that is IF it starts up just by hitting it with 55v like that. The application schematic would suggest there's no other way, since there's no actual communication going on - just DC going through the rectifier there...
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Old 01-09-2022, 01:20 PM   #9
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Put it this way. Anything that goes through that jack, has to go through the magnetics part. Sometimes these are inside the jack, other times it is separate. The problem is, that the magnetics need do be exactly as required. If you’d take ‘em out and put just jumpers in there, it will not work. Been there and done that.

Re reading your fist post again, I would get the spec sheet from the main ic, the buck converters maybe disconnect it one by one and see if the power becomes stable again.
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Old 01-09-2022, 01:36 PM   #10
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

The jack is just a connector in this case. The transformer part is most likely inside the black box. There could be a short there, as I checked most of the major downstream components, unless I missed something - will have to go over the board again....
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Old 01-13-2022, 02:07 PM   #11
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Had another go with this camera today. No dice: I still couldn't find anything to blame right away.

Out of curiosity, THIS is the injector it came with. It's the T8124 model. I had a look to see if it gives any info on how power is delivered and apparently it's a gigabit-capable injector, so it uses all 4 data lines - it doesn't send power over the spare pairs.....I THINK....that's why I said I don't quite get how POE works in a scenario like this....
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Old 01-29-2022, 01:34 PM   #12
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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
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Old 01-30-2022, 12:07 AM   #13
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Good to hear you got to the bottom of it.
Guess I was right in my first reply - thing must have gotten hit by a lightning / surge from lightning.

FWIW, I just repaired a Dell monitor earlier this week that had a shorted main IC on the video board. Don't know what caused it, but I suspect either ESR or power/lightning surge. Main IC only came in packs of 10... and those were about the same price as a replacement video board, so you can guess which option I went with.
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Old 01-30-2022, 10:21 AM   #14
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Nice repair momaka!
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Old 02-04-2022, 10:56 PM   #15
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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Nice repair momaka!
Thanks! But I take no credit in this repair whatsoever.
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Old 02-05-2022, 04:00 AM   #16
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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Thanks! But I take no credit in this repair whatsoever.
I think he was referring to the Dell monitor
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Old 02-05-2022, 09:33 AM   #17
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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I think he was referring to the Dell monitor


but your repair was cool too!
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Old 02-14-2022, 01:15 PM   #18
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

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but your repair was cool too!
Thanks... well, I just swapped boards. Very hard repair.
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Old 01-30-2022, 11:14 AM   #19
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Default Re: Axis Q6034-E Speed Dome cam No Power (teach me about POE)

Nice repair Dannyx!
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