Identify broken component on power board

[SUMMONER]

I have an old CCTV camera that went poof, evident by the smell of burned plastic and a crack in one of the chips on its power board.

camera: Jovision JVS-N5DL-HC
board: JVIPOWER247V1 0JL
chip: B P602 DEM

I would appreciate if someone could take a look and may be identify the chip/maker. A pointer towards a possible source for a replacement would be cool as well.

Thanks!

[peterb]

It’s a diode, judging by the PC marking - have you googled the number on the device?

[SUMMONER]

Yes, but nothing comes up that even remotely resembles it and it doesn't help that I can't even tell who made it. Never seen the 'B' logo before in my life.

Would be a shame to bin it, if all it needs is a couple of pence worth of parts.

[DanceswithUnix]

If I'm reading that PCB right, isn't that device directly across the 12V in connections?
That doesn't make a lot of sense, I have to wonder if that is a Zener to try and stop spikes from getting to the output, but then D3 seems to be a Zener not that I can see what that is doing either.

I have to wonder if the 12V in went nuts, and blew that component. But then it isn't obvious to me what that circuit is trying to do. What is special about the 12V out compared to the 12V in?

But I'm sure I would have failed my degree if I put a zener directly across anything when they should have current limiting resistors.

[Xlucine]

I agree that D2 looks like a zener. I think D4 and D3 are chained up to protect the output from reverse polarity

[DanceswithUnix]

I agree that D2 looks like a zener. I think D4 and D3 are chained up to protect the output from reverse polarity

From a quick google, SS34 on D4 is a schottky diode which looks like reverse polarity protecton, but on the output not the input. Back-feeding protection maybe? T10 on D3 comes up as a Zener, which I can't make sense of.

My only idea is that the output goes to a small reservoir capacitor, and this is the worst regulator ever built which would explain the fizzbang diode.

Ideally I think you need a scope to see what the input voltage waveform looks like.

I must be missing something, only D4 makes sense.

Edit: is there anything on the other side of the PCB?

[SUMMONER]

is there anything on the other side of the PCB?

Nope, just a serial number label.

So, shall I just solder a copper wire in place of the cracked chip and see if I can get the camera to catch fire/produce magic smoke?

I have tested the PSU from this camera with one of the other cameras and it appears to work fine.

[DDY]

So, shall I just solder a copper wire in place of the cracked chip and see if I can get the camera to catch fire/produce magic smoke? ...

I doubt the camera would release the magic smoke if you did that.

If the skid-marked component hasn't already failed to a dead-short, you'd be shorting 12V straight to ground with that wire.

The wire-short being the path of least resistance could pull a huge current - which the cabling or PSU may not be happy with especially if it doesn't have short circuit or over-current protection, and there would be hardly any voltage reaching the camera.

That said, the PSU might have SCP/OCP or might not be able to supply much current anyway, so if the component has indeed failed short then the camera won't get any power, so there's a chance that simply pulling that failed component might get the camera working again.

EDIT: I wonder if that failed component is a power diode for rudimentry half-wave AC rectification? So that the camera can run on either 12V DC or AC?

[SUMMONER]

Errr... you lost me there.

If I remove the cracked chip and bridge its pads with a wire I am removing any possible short, unless other components on the board have failed too. The question is, am I removing something that is essential to functioning of the camera?

If the entire pcb is just there to ensure a dodgy power supply doesn't kill the camera then I should even be able to bypass it entirely by wiring the 12v and ground pads on one side to the pads on the other side ? ¿

[DDY]

remove the cracked chip and bridge its pads with a wire...

That mystery component is connected across 12V and GND, you're asking for trouble by bridging it and therefore shorting the power supply by connecting 12V straight to ground.

Having looked more closely at the board, now I don't think it's a rectifying diode, but rather over voltage protection or a snubber.

You can't break it any more, I'd say pull D2 off the board, plug everything back in and see what happens.

[Xlucine]

Come to think of it, did the camera stop working after this failure or did you turn it off as soon as you heard the pop & smelled smoke?

[SUMMONER]

That mystery component is connected across 12V and GND, you're asking for trouble by bridging it and therefore shorting the power supply by connecting 12V straight to ground.

Having looked more closely at the board, now I don't think it's a rectifying diode, but rather over voltage protection or a snubber.

You can't break it any more, I'd say pull D2 off the board, plug everything back in and see what happens.

Oh.. got it. Looking at it now I see what you mean, the top pane is connected to ground. D2 might be permanently stuck in a state of shortening the entire circuit.

I will take it off and see what happens.

[SUMMONER]

Come to think of it, did the camera stop working after this failure or did you turn it off as soon as you heard the pop & smelled smoke?

Looking at CCTV footage I would say that it stopped recording moments before the smell, as I can not see myself walking up and down the corridor looking for the source of the smell.