Switched Mode Power Supply/Switching Power Supply (SMPS)

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Hi all. I have a question about a power supply. Input is 120vac. There are two outputs. One is a four wire 12vdc (two pos, two neg, hooked to a single pos and single neg output on the board) and the other is 52vdc (one pos and one neg). This thing runs a surveillance system (cameras and a DV recorder).

My question is this, should both outputs (12, 52) always have the rated voltage when the AC voltage is supplied to the unit, or is it possible one of them (the 52) would not show any (other than a small mv) until something triggers it and that is why it is called a SMPS? I wonder this because I do not see any other wires coming from or going into the power supply that would logically return a signal from the rest of the DVR to trigger anything. There is another PCB (you can see it in pic 3) on the side of the PS with another bunch of components. Part of it runs a 12 volt cooling fan, which is working properly. As I am reading this for errors prior to posting, I am wondering now if that secondary PCB may have wi-fi components, which would turn on the power supply (52V) to activate the recording?

The 12 volt side is producing 11-11.5 vdc. So I'm good there. The 52v side is not producing anything from the wire outputs. However, when I take a reading from the heat sink (which is attached to some mosfets/transistors and a diode) in the middle of the board (it has the number "2" on it), I am getting +51.5vdc to the chassis ground. I also get a steady 64.7vac (either probe) doing the same thing with the DVM set on AC. The DC voltage is not steady and goes up and down a fraction of one volt. Oddly though, the negative lead on the DVM has to be on the heatsink and the positive on the ground to get a positive DC reading. To my non-electronic educated self, that should make no sense. Based on the power supply box design, however, I do think some voltage should be there (on the heat sink), because the inside of the enclosure has insulation material positioned above it. By the way, don't ask me how I found out about the voltage coming off the heat sink.

Note that the original power mosfet, all other mosfets, and all of the transistors have been replaced, as have all of the caps. The diode was removed and checked. It is operating properly. All components were replaced with the same as what was removed, and before you ask, they were put back in the same way as they came out. I don't have the rest of the DVR to plug it in to test it, so I'm hoping that is the only reason I am not getting the higher voltage reading at the wire outputs.

Does anyone know if it is probably operating correctly, or what should I check next? I see places on the bottom of the PCB that may be test points, but unless a/the "switch" has to be activated for the 52 volt side, I don't know how to do that. I do not have a schematic. It is a Delta DPS-200PS-185B power supply.

Thanks in advance for your reply.

 

Thanks for the reply, Mr Kapp, however, this is a dual output voltage power supply. One side is 12vdc and the other is supposed to be 52vdc.

Maybe I didn't explain well enough. The 52 volt side only has two wires on it (red and white) and a two pin plug. The 12 volt has 4 wires (black and yellow) and a 4 pin plug, but both positives and both negatives in that plug are only attached to a single positive and a single negative output on the board. See the pic.

The 12vdc side is working. I am trying to get the 52vdc side figured out. I am wondering if there has to be a load on the output of the 52vdc side to get it to supply the current? And is there a workaround to get that current moving just so I can see if that side is operational or not. I don't have the rest of the DVR to attach it back into.

 

Thanks again, Mr. Kapp. I will try our suggestion in the morning. If it doesn't work, and I mean activate that 52volt side, I won't be able to sleep. Just better to be hopeful and think it will, so I can.

 

Ok. I took photos of the components attached to the center heat sink and the stand alone heat sink. For the center, number 1-13NM60N (Q801), 2- a diode-checks good, 3-F9NK90Z (Q501). Attached on the other side of component number 3, is a W9NK90Z (Q351). Q351 was definitely bad when I started troubleshooting this. The BR tests ok, as do all of the other resistors. The transistors and mosfets have been replaced with new components, because it was faster to order all of them new and just replace them from the beginning. The original .56 Ohm resistor next to Q351 had also failed and was replaced.

The component on the stand alone heat sink by the 52V output is a FML24S. It is new as well.

Just for piece of mind, the voltage (51.5vdc and 60vac) coming off of the heat sink is nothing to be concerned about? And the fact that I place the neg DVM probe on heat sink and the pos probe to chassis ground provides a positive DC voltage, is that normal?

And then there is this. I posted a photo of the bottom of the PCB. There are two contacts that, when out of the enclosure, have no conductivity, however, these would be grounded together when it is back in the enclosure. Would that have anything to do with my polarity concerns? I would think, if they were ground contacts, that they should be connected on the PCB as well.

 

Photos of the vertical PCB.

 

On the transformer where points 3 and 4 are (bottom of main pcb), I get 166vdc. I get nothing at numbers 8-9 and nothing at the smoothing capacitor. I should get some voltage at 8-9, shouldn't I?

 

Placing resistors across the outputs, either the 12V only, the 52 only, or both, didn't change anything.

 

Thank you, kellys eye. This is the controller chip. It is a CM6800UBX. I can find it, however, not in the US. Do I have to have this exact same number?

Another question. I had removed and tested the bridge rectifier earlier. It tested good at the time. While doing a closer inspection of the board, I found what appeared to be leakage from the "-" pin. I removed and tested it again and it still tested ok. I have ordered another one anyway. Could this have been part of the issue? Low voltage on the 12 volt side and no voltage on the 52.

 

As I was reviewing other's posts, someone had advised that the 52 volt side was the power supply for the IR lighting (surveillance system). That side would only come on when another component (light sensitive) was activated due to darkness. If that is the case, I am wondering if, quite possibly, that this PS is actually working as it should and that the nighttime trigger would electronically and then actually activate the 52 volt side.

The only problem with that is, unless the trigger is on the other part of the system, it would have to be done so by placing a load on the 52v output, because there are no other inputs to this power supply and only another 12vdc output that is showing only 10.9vdc. And I have already tested the output by placing an 18Kohm resistor (advised to use something greater than 10kOhm) and nothing changed as far as voltage. Actually I have loaded both sides to check them.

As far as the component replacement, most of them have been rather inexpensive, and this is only taking my time, of which I have plenty. I think I will do the CM6800 review, and will order the IC from China in the meantime. I am not done.

Thanks again, sir.

 

OK a new discovery. When testing the 12 volt side, I am not getting quite 12 vdc. It is low and jumping sporadically and constantly up and down between 10.4-11.9vdc.

I understand that an octocoupler between the main components of the board and the final circuit output should act like a diode and a transistor of some sorts. Additionally, they are partly responsible for maintaining a steady output voltage. I see the same octocouplers between both the 12 volt and 52 volt output sides and the main board components. If the octo on the 12 volts side is malfunctioning (non steady voltage) and the current draw and/or octocoupler activation on that side is the trigger for the other side (52vdc), could that quite possibly be my problem?

I've attached a close up of the octo on the 12v side (52 has the same one). I can find EL1013 octos, but not with the "445V." Looking at the datasheet below, there may be a correlation between the octos and the activation of the 52 volt circuit, because it appears they may "communicate" with each other somehow?

http://www.everlight.com/file/ProductFile/201407061745083848.pdf

I have tested both of them with the DVM and they do not react the same. Realizing that testing them in the circuit may give false readings, this is what I found. The 12volt side diode end (the side with the dot) is allowing current in both directions, and normally it shouldn't, if acting as a diode. The other end is showing open (no change on the DVM) from pin 4 to 3, but is allowing current from 3-4. The 52 volt side diode end is only allowing current from pin 1 to 2, like I would expect it would out of circuit. The other end is allowing current in both directions.

The ones on this board are glued down. I am afraid I may damage them if I try and remove them, but if your inclination is to remove and check them, I will. Is there something I should use on the glue to soften it without messing up the rest of the board?

Once again, your help is very much appreciated.

 

Whoops. I see I spelled them "octo."

All of the capacitors have been replaced with the same type and size and they have also been replaced correctly.

I will attempt at least partial removal of the "optos" and let you know. Prior to, I think I will do a precautionary localized schematic and define the current paths.

By your description, and functionality, it does sound as if they could be partly responsible.