12V 10A CCTV camera system power supply pulsating

[sam_sam_sam]

Re: 12V 10A CCTV camera system power supply pulsating


Maybe.

OK, did the donor transformer have the EXACT same primary and secondary side configuration in terms of windings, or not? This is actually really important.

The other thing that is really important when swapping transformers between PSUs is that the pins have to be matched exactly. For example, for the main winding on the primary side, one leg is always connected to the (+) positive bus on the primary cap (so +170V DC for locales with 115/120V AC mains and +340V DC for locales with 230/240V AC mains.) The other leg on the primary side main winding is always tied to the Drain of the MOSFET (or for PSUs with PWM-FET combo, to the Drain pins.) Likewise, the auxiliary winding on the primary side has two pins, and one should connect to primary side ground (negative lead of primary cap) while the other goes to a diode and a cap (SMD resistor R7 and diode D2 for your PSU). On the secondary side, obviously the output winding ground pin should be tied to ground and positive output tied to the anode of the rectifier. If any of these pins are reversed, the test won't work. So make sure to wire your donor transformer correctly. Like I mentioned, you can do that with jumper wires and the transformer floating above the PCB. Here's an example:
https://www.badcaps.net/forum/attach...1&d=1608943994

Now, if you did all of that above and the results are still the same, you can also do the reverse - that is, try the transformer from the power adapter from this thread into the adapter where you got the donor transformer from. If the donor power adapter ever worked correctly, your transformer should work OK in it too.

And as always when testing these, I suggest using the series incandescent bulb, just in case. At least IME, most flyback topologies are not too picky about the transformers. I've even used the 5VSB output from an ATX PSU to drive another transformer to test it out.

I have a couple of questions first of all how do you know weather or not the switching transformer has the same configuration as the one that you think is similar configuration but a different voltage how would that work if the feedback back circuit is looking for certain voltage

Also the link that you posted is having an issue not being found

Can you please go into more details about how to make sure that the configuration of switching transformer are the same for doing this type of testing because I really interested in because I follow your advice on how to troubleshoot switching power supply in the past and thank for your advice and insight on this topic

[sam_sam_sam]

Did you by any chance test C10 out of the circuit with a capacitor tester if so what is the value of the capacitor and what reading did you get testing it I have seen this type of capacitors go bad before

Also any capacitor that is that type as well besides that I not completely convinced that the switching transformer does not have some kind of issue because once I had a switching power supply that had a weird issue that I had not seen before and I had changed the switching power supply regulator and I switched transformers because I have several of the same model number and when I switched transformers and power up the power supply it blew up the switching power supply regulator because the switching power supply board worked fine but with some other kind-of other issues but it did power on but acted weird went you would try to load it near it is supposedly current rating

The reason I mentioned this because a ring tester does not always tell you weather or not a switching transformer is bad unfortunately because I got the same results from both switching power transformers

[harp]

Re: 12V 10A CCTV camera system power supply pulsating

You can NOT feed an external voltage to pin 7, If you connect an external power supply ground to this power supply HOT ground you will blow it up.

R_J, can you please explain how exactly external psu will blow it up, current pathway?
Supose to both wall psu adapter have not direct ground pin.

[rddube]

Re: 12V 10A CCTV camera system power supply pulsating

I am still saying it acts like there is something high in resistance or open somewhere on this darn thing.

I checked almost every component, changed the output capacitors, etc. Redid all soldering and even changed the PWM chip again just to make sure. Same symptoms.

Starting to think there is something wrong with the transformer but did check that too and it's a complete mystery!

[CapLeaker]

Re: 12V 10A CCTV camera system power supply pulsating

I am still saying it acts like there is something high in resistance or open somewhere on this darn thing.

[rddube]

Re: 12V 10A CCTV camera system power supply pulsating

Ok, so I gave this thing a last shot and redid all the soldering on the entire board thinking it might be the solution, but alas, no still the same erratice voltages. On the startup cap, I get between 11.6V to 15.2V jumping around in between.

[petehall347]

Re: 12V 10A CCTV camera system power supply pulsating

would be nice to find out what is the fault after 6 pages ,,
just noticed the last voltages are ac so that threw me a little .
whatever it is will be something really silly as those things get overlooked often . most of my call outs turn out that way after the so called experts have had a go at whatever it was ,

[CapLeaker]

Re: 12V 10A CCTV camera system power supply pulsating

I wouldn’t trust this psu anyway much and replace it with a Meanwell that fits.
This being said, I would use this old power supply as an “educational” piece. Maybe even put it on the side in later to fix pile when the weather gets bad or you are bored or something. Then go at it again. I did this a few times and the end was successful.

[rddube]

Re: 12V 10A CCTV camera system power supply pulsating

Hey Harp, I appreciate your help and the effort in trying to diagnose this, but I am at a point where it's almost a no go with this thing! I think I'm going to try what Alimash suggested and if that doesn't revive it, well it will have been a long adventure..I'll keep you posted on my resoldering of the whole board.

[Alimash]

Re: 12V 10A CCTV camera system power supply pulsating

Just a thought, a similar issue happened to me, and i solved it by simply resoldering the whole board, it turns out some joints has moisture.
It took me a lot of time to figure it out.

[lotas]

Re: 12V 10A CCTV camera system power supply pulsating

i would be changing the 1.5 meg resistor first .

Yes, it can be reduced a little and set to 1.2 MOm.

[petehall347]

Re: 12V 10A CCTV camera system power supply pulsating

i would be changing the 1.5 meg resistor first .

[harp]

Re: 12V 10A CCTV camera system power supply pulsating

Allmost all jumping arround...

It is kind of contradictional, but it is what it is. Mosfet is out. Mains 163v have two big capacitor and nothing to load, but it is present 0.6v ocasional ripple...
Pin#3... it is now only connection with power through 1.5M resistor.
Pin#6... sense resistor flow 10mA for nothing?

So, desolder IC from pcb (no mosfet no ic from now), and do DC and AC measurement on IC pads, I am interesting is still pulsating... do same DC reading on secondary output without load.

Pause here to discuss on forum with results...


Next I will do, is to desolder everything, but everything at all on primary side, clean pcb truely, inspect every (unpopulated) track end-to-end and double-time for 0.0 ohm resistance and visual.
Check separate each desolder component, make note... I suggest that not soldering it back that component, but use some other from scratch board.
For 000 resistor use instead a wire, and ommit placing any extra unnecesary component apart from bare bone test IC circuit, use IC socket on now on, it is possible that ic (batch) is faulty.
Then scrape on pcb a little notch in isolation coating like tear shape next to every THT pin, to reach fresh copper, put back fully tested component in a fully tested track and stretch tin solder to flow this area.
After soldering each component, test fot continuity and shorts with near area.

Suggestion from others?

[rddube]

Re: 12V 10A CCTV camera system power supply pulsating

Hello everyone, sorry for the delay in replying, have been extremely busy at work and was just completely exhausted by the time I could get to work on this. It's the weekend now, so here goes, measurements of all ic legs without mosfet in AC setting mv:

Pin 1 - 0mv
Pin 2 - 0mv to 478mv jumping around in between randomly no fixed delay
Pin 3 - 0mv to 622mv jumping around in between randomly no fixed delay
Pin 4 - 0mv to 462mv jumping around in between but synchronously, like it was timed
Pin 5 - 0mv
Pin 6 - .8 to 2.2mv
Pin 7 - 0 -657mv jumping around randomly no fixed delay
Pin 8 - 154mv to 420 mv jumping around randomly no fixed delay

Output without load and mosfet is .02DCV

[petehall347]

Re: 12V 10A CCTV camera system power supply pulsating

any news yet ?

[harp]

Re: 12V 10A CCTV camera system power supply pulsating

Please do exact measurements of all ic legs (without mosfet) in AC setting mV.
Also, check the output DC without load and mosfet.

Till now, I was thinking that jumping oscilations came from mosfet who try to start transformer windings... when is mosfet out, the transformer is disconnected from current path? From where the exactly same oscilations now came from?
Seems to the big current is not involved anyway...

[CapLeaker]

Re: 12V 10A CCTV camera system power supply pulsating

Crazy thing. You did get kind of a different result if I compare your last results with those in post 122. But yet the darn thing does kinds the same shit what it did before. Now I am out of ideas, besides replacing every component one by one. Personally I think something went high resistance or open.

[rddube]

Re: 12V 10A CCTV camera system power supply pulsating

Ok, so took the readings on the PWM without the primary mosfet in and fixed the suspicious solder joints (I think I've now reflowed the whole board ):

Results

Pin 1 - GND
Pin 2 - .1V to 1.2V jumping around
Pin 3 - 16V to 19V jumping around
Pin 4 - .012V to .263V jumping around
Pin 5 - .2V to .86 V jumping around
Pin 6 - 0V
Pin 7 - 12.4V to 15.7V jumping around
Pin 8 - .292V to 1.18V jumping around

[CapLeaker]

Re: 12V 10A CCTV camera system power supply pulsating

Btw fix that solder joint on point A. Looks to me suspicious. Matter effect reflow all them solder joints that you
A: didn’t touch yet
B: looking shady like point A in the picture.

[CapLeaker]

Re: 12V 10A CCTV camera system power supply pulsating

Now run this PSU without the mosfet and measure the pins on the PWM