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  • Author Author: ralphjy
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NVR Died

ralphjy

The NVR that I use to store my ip surveillance camera video just died.  it has been running continuously for 14 months.  My experience with electronic equipment that runs 24/7 is that things tend to die in the 3-5 year timeframe.  Usually it's the power supply, especially if it's a wall wart.  Or with NVRs, DVRs, or network storage, it is usually a disk drive.  The unit is an Amcrest NV4108-HS 8-channel HD NVR.

 

I noticed that the unit was not functioning when I tried to view some recorded video.  When I checked it there was no power indication (no LEDs lit, no fan or disk noise).  I was hoping that it was just the power supply (12V, 2A wall wart) but unfortunately it looks okay with a resistive load.  So, now I'm on to troubleshooting it.

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I had initially tested the power supply with a 25 ohm load, so I tried again with a 5.1 ohm load just to make sure it could handle the 2A rated current.  The voltage dropped a couple of hundred millivolts but that was probably due to the small gauge wire.  So, the power supply looks fine.

 

I put a DVM across 12V to ground and measured a dead short.  The current limit on the power adapter must be protecting the adapter from damage.

 

Here's a look at the inside of the NVR:

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And a closeup of the PCB:

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A close inspection of both sides of the PCB did not show any obviously damaged or burnt components.  Unfortunately, I haven't been able to find a schematic for this board.  I'm pretty sure that it is manufactured by Dahua who is an OEM supplier for Amcrest and many others.

 

I identified a couple of components that I thought could possibly short the power supply.  The first was obvious - a 220uF electrolytic capacitor that is just behind the power jack.  I removed it but the short was still there and the capacitor checked out okay.  I was hoping to find other electrolytics or voltage regulators (I assume that there is at least a 5V regulator).  I did find an adjustable regulator but its input is not attached to 12V.  Wish I had a schematic......

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I did not pull the heatsink off what I assume is the primary ASIC mainly because I doubt that it would be directly tied to 12V.  At this point I think that I may just give up unless someone has any good ideas.  Normally, if I had a schematic I would try to push some current into the rail and try to determine where the short is.  Without a schematic it would be hard to figure out where to measure.  If I felt lucky I could just crank up the current and watch for the smoke but I'm not in the mood to try that.

 

Unfortunately, I was hoping to use the NVR as a video source for my Path II Programmable project so I need to think about a replacement.  The Amcrest unit functioned very well but it is quite disappointing that it had an early death.

 

At least I should be able to repurpose the case and I'm pretty sure the hard drive is still good - I guess I should verify that next.

  • in reply to ralphjy

    Hmm. I wonder if your power brick might have an intermittent feedback winding or optoisolator connection. Transient overvoltage would be the only thing I can think of that would harm most ICs. Problem is if it was truly shorted, there's a slim chance the output of the converters may have been unregulated/up to full input voltage as well, causing collateral damage.

     

    Things like TVSS diodes on most hard drives may fail shorted in response to overvoltage, removing them may allow the drive to function if they are damaged.

     

    Not sure whether this patient can be saved ...

     

    - Gough

  • in reply to shabaz

    Hi Shabaz,

     

    My reason for using the NVR for the PIIP project is just to get stored video to analyze (I'm also going to use live camera feeds but I don't store video on the camera or in the cloud).  The IP cameras and the NVR have internal webservers that will provide an RTSP video stream over the network.

     

    As you suggest, it probably will be worthwhile removing those capacitors and then the DC-DC converters if the caps are okay.  I can't determine what the specific converter is.  All three of the 6 pin ones are labelled the same.

    image

     

    But it seems that for the few buck converters that I've looked at that there is a standard 6 pin SOT footprint.

    image

     

    And all 3 of them show shorts between Vin and Gnd (pins 5 and 2).  So, a good place to start.

     

    Unfortunately, I probably need to get another soldering iron to do this efficiently.  It seems that they are using lead-free solder (probably a good thing) as I'm having a difficult time getting the solder off the board.  And as I mentioned to John, I'm quite busy so this will need to be a background task.

     

    Ralph

  • in reply to Gough Lui

    Hi Gough,

     

    I always look for electrolytics and tantalums first.  Interesting that the only one electrolytic that I see is the one that I removed at the input.  Good suggestion to take a closer look at the output of the power brick.  I'll take a look at it with an oscilloscope.  I should make it a habit to do that for all my stuff.  I started to do that with other wall warts that I use.  I've had bad experiences with a lot of the 5V 2.5A supplies that are sold for/with the Raspberry Pi.  There's a particular brand - Rhino that Fry's Electronics sells that are consistently bad in terms of output ripple.  I've noticed that they are selling them for $1 now. 

     

    Ralph

  • in reply to jw0752

    Hi John,

     

    Thanks for your suggestions.  I don't currently have access to a thermal camera but that's a good idea.  I do have a power supply with variable current limiting that I could use.  I have to admit that in the old days I did my share of trace cutting to isolate faults.  But like you said nowadays with multi-layer boards and power and ground planes it's quite a bit more difficult.  Probably removing components is going to be the best approach.  I'll need to ponder this a bit.  I've got a few irons in the fire and I wasn't looking for another project but I guess curiosity always get the best of an engineer image.

     

    Ralph

  • Hi Ralph,

    When checking the circuit with your meter be aware that the color of the probes may not accurately indicate their polarity. It's best to use a second volt meter to verify which ohmmeter probe has the positive potential.

    John