12V 10A CCTV camera system power supply pulsating

[rddube]

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

Installed a third TL817 (correctly) and doing the same thing, this time pulsing from 3V to 6-7V with sometimes showing 4V - 5V erratically.

[rddube]

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

The reference voltage for tl431 is 2.5v

And install the TL817 ortron correctly (1-2 pin on the cold side, 3-4pin on the hot side).

Hi, it was installed correctly, it is me that reversed the reading. And when installed (correctly), we are back to square one whereas the output pulses between approx 4V to 6V-7V.

[lotas]

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

The reference voltage for tl431 is 2.5v

And install the TL817 ortron correctly (1-2 pin on the cold side, 3-4pin on the hot side).

[rddube]

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

Ok, so I double checked to make sure I am giving you the right pins on the AZ431 (TL431), this is with the optocoupler out:

Reference: 2.6V steady
Anode: OV
Cathode: 1.8V steady

As a double check, I reproduced them (in yellow) on the photo attached (the adjustable resistor is in place however).

[rddube]

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

The TL431 is the voltage reference ic. And the EL817 optocoupler is installed with pins 1&2 on the secondary side, correct
From post 19
This should not be enough voltage to turn on the optocoupler led, and cause E-C to conduct.

What are the voltages on the reference ic with respect to ground

I'm terribly sorry, I was looking at this upside down again and got things reversed. Really really sorry, I'll make sure I double check before writing stupid things. I'll get the voltages on the TL431 (the right ones) and report back. Thans for your patience.

[lotas]

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

Oh R_J, this power supply has the pins 1 & 2 of the optocoupler on the primary side! That's how it was installed originally, the small dot being the pin 1 ?

It is not right.

[rddube]

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

Oh R_J, this power supply has the pins 1 & 2 of the optocoupler on the primary side! That's how it was installed originally, the small dot being the pin 1 ?

[R_J]

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

The TL431 is the voltage reference ic. And the EL817 optocoupler is installed with pins 1&2 on the secondary side, correct
From post 19

Finally, measured voltage on secondary side of optocoupler which oscillates between .1V and .6V-.7V

This should not be enough voltage to turn on the optocoupler led, and cause E-C to conduct.

What are the voltages on the reference ic with respect to ground

[rddube]

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

Sorry R_J, but is the TL431 the optocoupler - in post #6 it is talking about TL431? The original optocoupler is the one in the first photo (a bit blurry but it is EL 817), I had replaced it with the one in the second photo with same results.

[R_J]

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

The pot is there to adjust the 12v output, try adjusting it.
In post #6 you were asked about the optocoupler and said

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

What is the number on the optocupler? It is installed the correct direction as I can't see it clearly? I would replace it

[rddube]

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

How much effect does adjusting the 1K pot have on this power supply?

I don't really know, I have never adjusted that pot in the past. I tried looking for a schematic but I don't think any exist?

In my reasearch I did find this video, but I think we've tried most of that:

https://www.youtube.com/watch?v=YbUftLuvODg

[R_J]

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

How much effect does adjusting the 1K pot have on this power supply?

[rddube]

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

So something on the secondary side around the reference ic is likely the problem, When the opto coupler is connected, it pulls pin2 of U1 low puting into burst mode.
What is that stuff on C6, the blue disc cap?

It's some sort of glue, you can see the same stuff on the back of the power supply where the screws are. I checked C6 (unsoldered it) and it measures good. I didn't unsolder C10, but I could if you think that could be the problem?

[R_J]

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

So something on the secondary side around the reference ic is likely the problem, When the opto coupler is connected, it pulls pin2 of U1 low puting into burst mode.
What is that stuff on C6, the blue disc cap?

[rddube]

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

Had changed the AZ431 (post #35). Pin 2 is showing erratic voltage between .101V to 5.9V jumping in between just like for the 12V output mentionned in post #66.

Thanks for hanging in there R_J!

[R_J]

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

So it would seem the regulation for the optocoupler is causing the problem, can you change the AZ431 (TL431 etc)

Is Pin 2 of the ic sitting at around 6v when you tried this? My guess is the optocoupler led is being turned ON causing the photo transistor on the primary side to conduct shutting down the ic. A bad reference ic could be the cause.
My guess when the power supply is working properly, pin2 FB would be around 2~3 volts

[rddube]

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

Everything put back together, optocoupler unsoldered on primary side, I get erratic from 14V to 21V and anywhere in between on the 12V ouput.

[rddube]

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

ok will do and report back.

[R_J]

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

I would put things back as they were and try unsoldering the primary side of the optocoupler and see what voltage you get on the 12v output, this may not work because of the ic protection circuit. Something is telling that ic to be in burst mode. There are not that many components that can cause this.

[rddube]

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

It was not supposed to change, But did D2 provide any voltage to charge the temporary cap I asked to connect to the disconnected D2? If the temporary cap DID charge, then the feedback winding, d2 etc is working, and the problem is else ware.

Ok R_J, you are right I just forgot why we were doing this test (getting old I guess ). Ok, so yes the cap charges very well up to 13.2V very steady and when I remove mains power, cap discharges gradually but very slowly.