Group Actions
Engagement
  • Author Author: ralphjy
  • Date Created: Date Created
  • Views 2627 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

  • Hi Ralph,

     

    The chances of finding the problem when it is a shorted power in line are usually pretty good. I would begin with an ohm meter probe on one of the power input wires and then I would look at all the semi conductors that are close to the power input. We are looking for any that are directly connected to the power rails. There is perhaps a diode that was being used for polarity protection. The diode could be one of the 3 legged SM components as many of these are diodes and not transistors. You mentioned putting power on the input and looking for smoke. Perhaps you could modify this idea and put just a little power in and use an infrared viewer to look for where the heat is going. You may be able to see the warm traces leading up to the shorted component. If you do not have an infrared viewer you might be able to use a small thermistor and move it around while watching its resistance. Traditionally I would cut traces and eliminate circuit branches to trace down the culprit component but these newer SM boards are not as easy to do this with. Still you might look to see how far you can follow the power traces and if there is a place where you can put a bunch of components on one side and another bunch on the other side cut the trace and see which side the short is on. You can always scrape the masking from the trace and put a solder bridge back after the bad component has been removed. If I think of anything else I will add later.

     

    John

  • 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

Comment
  • 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

Children
No Data