DVR power supply testing

[Ed Sowell]

This is in regard to a failed Lorex LNR 4082 security camera DVR. One possibility is the power supply. See attached photo. The label says the DC output is either 12v or 52v. I suspect the former is for 120VAC input and the latter for 24VAC input. Don't know for sure.

There are lots of YouTube videos of testing desktop PC power supplies. This this one is quite a bit different, and I don't really know which wire pairs to test.

As you can see, there are 2 cable bundles:
(a) one with 2 black and 2 yellow wires
(b) another with a red and a white wire.

Suspecting black is ground, I tested black to yellow, getting 10.8VDC.

Also tested white to red (0 V), black to white(0 V ), and black to red (0 V).

From this I surmise that power is provided through black & yellow, and the voltage is too low. And perhaps the red & white pair is connected to an on/off control button.

So, am I correct?

BTW, I posted earlier on another possible culprit, a possibly heat-damaged board component.

 

[kellys_eye]

Black/yellow are commonly 12V (as in PC supply wiring) and the red/white is probably the 52V supply. You could determine this if you took the cover off the PSU and saw where the wires were connected - there' will be some 16V electrolytics across the 12V supply and 63V (may be 100V) electrolytics on the 52V line.

Show the innards of the PSU and I suspect we'll see some damaged parts.....

 

[Ed Sowell]

Ok, here's what it looks like inside. I see nothing that looks damaged, but I have little experience at this. One thing that is clear is Kellys_eye was right. White to Red is supposed to be 52v and Black to Yellow is supposed to be 12v, according to markings on the board. Since I measure 0 White to Red and 10.8 Black to Yellow, something's wrong.

Let me know if there's another photo you need to see, or something to inspect or test.

 

[Ed Sowell]

Sorry for the replicated photos. There's no feedback that the upload worked and I do it again to be sure. Is there a forum "how to" somewhere?

 

[kellys_eye]

You can hit the 'edit' button on your post (up until another post is added to the thread - and your own post 'locked' that ability....) and delete/modify the content of your post.

Yeah... pictures don't actually help much. You'd have to dismantle the PSU a bit more and spread the innards about a bit.

Bad luck (for you) is that replacement PSU's of that model seem hard to come by so a repair is about the only route open to you unless you can find something that gives out the right voltages/currents and can fit (physically)....

If you are determined to get this unit going you need to get the voltages working so are you ok with stripping the PSU down still further? i.e. remove the circuit board and expose it in all its glory????

 

[H2814D]

In looking at your pictures, along the left side there is a transformer (MP-130I -written upside down). Just above that transformer is a small capacitor that appears to have a slight bulge on top. There is a component with copper and red wire windings directly above that cap and what appears to be a diode right next to it. If that cap actually does have the bulge as it appears, you may want to remove and test that first. The cap I am looking at is below the black two lead wire (red and black) that, I think, goes to a fan. That cap may be the source of your low voltage problem on the 12V side. Let us know what you find please.

 

[Bluejets]

Yes, in the second photo, looks like that to me as well.

 

[Ed Sowell]

You can hit the 'edit' button on your post (up until another post is added to the thread - and your own post 'locked' that ability....) and delete/modify the content of your post.

Thanks.

Bad luck (for you) is that replacement PSU's of that model seem hard to come by so a repair is about the only route open to you unless you can find something that gives out the right voltages/currents and can fit (physically)....

I find them listed, admittedly sometimes used.

If you are determined to get this unit going you need to get the voltages working so are you ok with stripping the PSU down still further? i.e. remove the circuit board and expose it in all its glory????

Yes, I can do that. The focus seems to be on capacitors. I've never tested a capacitor but willing to learn. I have a pretty good DVM, and a signal generator and oscilloscope (inherited). As owner of a '76 Jaguar, I've used the DVM a lot, but the signal generator and oscilloscope rarely.

 

[H2814D]

Ed...Common visual indications of bad capacitors are leaking and bulging. If the top of the one I identified is actually bulging, and not flat like most of the other ones we can see, that is likely where you should start. You will have to remove (un-solder) it from the board to check it. If your DVM has a "Cap" setting, use that. Take the negative lead and put it on the negative side of the cap. There should be a stripe, usually in a contrasting color to the rest of the cap, with a "-" sign on it. In your case most of the cap is black. The negative side is white/gray. You can see it in the pic. Remember which way it came out, so you can replace it with the negative side in the same hole in the board when you go to replace it. Take the red lead of the DVM and hold it on the other cap lead. Hold both of them on the cap until your DVM provides a reading. It may take a few seconds, but it should come up. On the side of the cap there should be a capacitance rating, usually in uF. The reading you get from the DVM should be within 10-20% (probably 20) of the rated capacitance. If it is within that range, a likely good cap. If not, replace it. If it is bulging or leaking, replace it. Oh, and lastly...let us know what you find and if you fix it.

 

[Ed Sowell]

I see no bulging on any of the 5 capacitors. The semicircular brightness on the top at the right in the photo is probably an artifact... perhaps a reflection of the camera flash.

My DVM doesn't have a capacitance setting, so all I could do is measure resistance. A quick look online suggests a cheap one that does is about $30, and the one I looked at had poor reviews. Since there seem to be 5 capacitors with none looking suspicious to me, it would be a lot of work to track down the culprit. Think I'll take another look at the availability of a new power supply before going that route.

Thanks for your help.

 

[H2814D]

Just so we are clear, I wasn't talking about the capacitor on the top right of your photo. The one I am talking about is in middle on the left, under the black wire that goes to the fan. There are three larger ones on the bottom- two black and one that looks green; a smaller than the rest black one in the middle of the board-the one I am talking about; and another large one on the top right. Would you be able to take another picture of just the smaller cap in the middle of the board showing the top of it clearly and from a slightly side view.

 

[Ed Sowell]

I pretty sure we're looking at the same one, the second one below.

 

[H2814D]

The second picture. The smaller cap that is by itself. It still appears to have a slight bulge on top. You should just replace that one and see if your voltage returns to the rated voltage on that side. You said the 52V side was correct and the 12 volt side was at 10.8. Oh...looking back through the posts, you did not say the 52V side was correct.

 

[(*steve*)]

In the first photo above, it looks like something has leaked over the board near where the white wire connects to it.

It may be simpler (and quicker) to find replacement caps for all the electrolytics, and just change them all. It's relatively cheap and if it doesn't change anything you know its not the capacitors.

 

[Ed Sowell]

In the first photo above, it looks like something has leaked over the board near where the white wire connects to it.

It may be simpler (and quicker) to find replacement caps for all the electrolytics, and just change them all. It's relatively cheap and if it doesn't change anything you know its not the capacitors.

Steve, you have a lot more confidence in my soldering skills than I do. Thanks! But I'm thinking about trying. Turns out that the online offerings of a replacement PS assembly is "on back order".

 

[Ed Sowell]

The second picture. The smaller cap that is by itself. It still appears to have a slight bulge on top. You should just replace that one and see if your voltage returns to the rated voltage on that side. You said the 52V side was correct and the 12 volt side was at 10.8. Oh...looking back through the posts, you did not say the 52V side was correct.

.
It looks ok to me, but as I said I'm no expert.

BTW, what is the blue component on the attached (daughter?) board? Small capacitor?

 

[davenn]

The second picture. The smaller cap that is by itself. It still appears to have a slight bulge on top

naaa, it looks good

 

[Ed Sowell]

Trouble is, I'm the only one who can see the components instead of photos and to me, the least able to judge, they all look good.

What are the chances it's a different component that has failed, e.g., a transistor? Does 0 volts White to Red offer a clue? It should be 52 volts.

 

[Ed Sowell]

I think I see a damaged resistor. At one end, there's a blackened spot that could perhaps be burned-off casing. The lead at that end is discolored where it emerges casing.

Could this be the culprit?

 

[Ed Sowell]

There's no connectivity though it.