12V 10A CCTV camera system power supply pulsating

[rddube]

Hello everyone,

I've been working on trying to resolve why this power supply doesn't work properly i.e. it pulsates from 4 to 6-7 volts on the output and the green led even pulsates.

I've checked pretty much everything on the board, all capacitors are good as they were all taken out and tested (except for the blue ones), I changed the OB2269AP chip for a new one, checked all mosfets, nothing goes!

I changed the optocoupler as I read in another thread that that may be the culprit, but to no avail.

Need some help from the grand masters! Thank you!

[stj]

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

did you check the output diodes?
ideally with a load

[harp]

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

Not grand master, but check the gate that do not floating, surround resistors...

[rddube]

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

did you check the output diodes?
ideally with a load

Hi stj,

Presume you mean these? They are a SR301Q0CT.

I did check them by takeing that component out and with my multimeter they both tested good. How would I do that with a load (still learning)?

Many thanks!

[lotas]

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

Did you change the TL431?

[rddube]

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

Did you change the TL431?

No, but I did pull it out and tested it with my component tester and it tested good.

[R_J]

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

Replace the small electrolytic C4? near the ic

Do you have any load on the power supply output? if not it might be in burst mode.

[rddube]

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

Replace the small electrolytic C4? near the ic

Do you have any load on the power supply output? if not it might be in burst mode.

Hi R_J. I did replace C4 it is a 10uf 50v cap. Here is another photo with voltage readings, and you'll see where the pulsating starts on the primary side.

[R_J]

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

What is the voltage on Pin #7 of U1?
What is the voltage on pin #2 of U1?
Do you have a load on the power supply?

[lotas]

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

Your OB2269AP may be defective, substandard, it has been supplied many times, many PWMs are now on the market with defects (you take them from one batch - they don’t work, you buy them from another place - everything works).

[rddube]

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

What is the voltage on Pin #7 of U1?
What is the voltage on pin #2 of U1?
Do you have a load on the power supply?

Pin #7 of U1 is oscillating between 9v to 13v-14v
Pin #2 of U1 is oscillating between .10v and .20v
I tried with a load on the power suppy, but doesn't even power a 12V fan...

[rddube]

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

Your OB2269AP may be defective, substandard, it has been supplied many times, many PWMs are now on the market with defects (you take them from one batch - they don't work, you buy them from another place - everything works).

That could very well be the problem. I purchased these on Ebay from a seller that had 100% feedback, but you never know. I got 5 chips, but they seem to be all from the same batch. Will try to switch and report back. Might even try to reinstall the original one and see. If nothing works, I will order others from a different source. This sucks, if such is the case. Tks Lotas.

[sam_sam_sam]

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

Your OB2269AP may be defective, substandard, it has been supplied many times, many PWMs are now on the market with defects (you take them from one batch - they don't work, you buy them from another place - everything works).

What happened to quality control it does seem to exist if it is a crapshoot if you get a good or not REALLY

[rddube]

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

What happened to quality control it does seem to exist if it is a crapshoot if you get a good or not REALLY

Well did the tests with another one from the same batch, same result - pulsating. Removed it, put in the original OB2269AP, same result. Went hunting in my scrap boards and found one that seemed intact, so tried that one same result!

What is weird, is when I remove C4 and test, I get no more pulsing on the top pin of R10 (a nice clean stable 18V), but then I get no output on the secondary side, nothing?

[CapLeaker]

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

Funny… I just repaired a Northern NVR with 16 cameras two days ago where the power led was blinking and didn’t want to boot. Problem was a bad 16v 1500uF capacitor on the output. Changed the cap and put the NVR back in service. Took me like 30mins to fix. That was an easy repair.

Did you check the primary capacitors?

[R_J]

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

Check that the feedback winding on the transformer is not open, check R7 and check D2.
C4 gets its initial charge via R10, then once the supply starts, C4 should get charged via D2.
Pin 7 vdd needs to be at 16.5v or above for the ic to operate.
I would also check the voltage across the optocoupler (secondary side) If it is high (1~2v) it may be turning on the optocoupler and taking pin2 low, shutting down the ic.

[stj]

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

100% feedback is a bit suspicious.
i'm happy with sellers in upper 90's - your gonna get unhappy customers because of poor postal system or just idiots buying stuff they didnt need

[lotas]

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

Yes, it needs to be checked under load, load a 12v car lamp at the output.

[rddube]

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

Check that the feedback winding on the transformer is not open, check R7 and check D2.
C4 gets its initial charge via R10, then once the supply starts, C4 should get charged via D2.
Pin 7 vdd needs to be at 16.5v or above for the ic to operate.
I would also check the voltage across the optocoupler (secondary side) If it is high (1~2v) it may be turning on the optocoupler and taking pin2 low, shutting down the ic.

Not sure which is the feedback winding so I indicated where I think it is in the attached photo with the resistance reading. R7 reads 25 ohms, and D2 I pulled out and tested with multimeter in diode mode and it seems fine.

When you say C4 gets its initial charge via R10, you mean via pin 7 of the chip, because I don't see how C4 could get charged via R10 ? Pin 7 is oscillating between 9V- 13-14V. Finally, measured voltage on secondary side of optocoupler which oscillates between .1V and .6V-.7V.

[rddube]

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

Yes, it needs to be checked under load, load a 12v car lamp at the output.

Ok, did try it with a 12v car lamp, but doesn't even show any sign of voltage, no glow at all not even pulsating.