12V 10A CCTV camera system power supply pulsating

[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

[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