Group Actions
Engagement
  • Author Author: ralphjy
  • Date Created: Date Created
  • Views 2677 views
  • Likes 6 likes
  • Comments 9 comments
Related
Recommended

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.

image

image

 

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:

image

 

And a closeup of the PCB:

image

 

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......

image

 

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.

Parents

  • I would suggest you try isolating as much as you can.

     

    I'm not sure if you have tried, but see what happens if you try to apply 12V power without the fan and hard drive attached. If the board is still shorted, then it's a good sign that the fault is not in the hard drive or fan. If the short disappears, the fault might not be in the fan and hard drive but could be related to the behaviour of DC-to-DC converter under load.

     

    The next thing is to find a friend with a thermal imager - but if you don't know anyone with one, I find a finger works fine too. My suspicion is that you might have a DC-to-DC controller that has a shorted MOSFET - so try touching each of the chips near the inductors on the board (i.e. bottom edge, near the centre near the SoC) to see if any of them are hot. Similarly with the inductors which might give a clue.

     

    If not, then the next step might be to feel and carefully examine any electrolytic capacitors. If there are any tantalum capacitors, they are a prime suspect as well as some have a power-on-short failure mode which is known.

     

    If you do have a failure in the DC-to-DC controller ICs, it may be a sign that your power brick isn't a great quality unit. It could have been affected by a mains surge or more likely, it may put out spikes or high ripple which may have stressed the converters.

     

    - Gough

  • 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

Comment
  • 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

Children
No Data