12V 10A CCTV camera system power supply pulsating

[CapLeaker]

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

Ok, cleaned the probes and deoxed them, but the lowest I get with very high quality probes is .5 ohms, there is no way to 0 it. Whereas the cheaper tester Tais TA118A is dead 0 ohms when connecting the 2 probes together. It cost +- 40$ compared to the Fluke 87 V which had cost me over 500$. Probably need calibration and cleaning, but they're asking over 300$ CAD to do this at Fluke, not worth it.

If you get real good probes, you will get it down to 0.2ohm. Flukes usually do not go down to flat zero as it measures the resistance of the leads. She is fine and well within tolerance.

[harp]

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

It is not neccesery to remove secondary diode again, unless (like I mentioned before) you feed 12Vdc to output and simultaniously power psu from mains 220Vac, due to specific testing purpose.
So yes, just feed 12v and check again pin1&3 of TL431 and primary side of optocoupler, maybe to try reverse probe, or other dmm... if in off state is 3k reading accross pin3&4 of opto, then when interLED power on must be some lower reading, dont you think?

[rddube]

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

Open the fluke and clean pcb rotary switch with contact cleaner, and its parts in plastic on button side.



Optocoupler have npn inside, and when lights go on, resistance go rapidly down. Check this whats are going on, even it is not your primary problem. When you feed secondary with 12v, you must have about 2.5v on tl431 reference pin1.

Ok, will try that for the Fluke.

For the 2.5V, you want me to remove the output diode and test again injecting 12V in the output side?

[harp]

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

Ok, so I guess my old Fluke needs calibration

Open the fluke and clean pcb rotary switch with contact cleaner, and its parts in plastic on button side.

The optocoupler is maked EL 817 - this is the 3rd optocoupler, but I think they are all good

Optocoupler have npn inside, and when lights go on, resistance go rapidly down. Check this whats are going on, even it is not your primary problem. When you feed secondary with 12v, you must have about 2.5v on tl431 reference pin1.

[rddube]

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

Probably doesn’t need calibration, rather a good cleaning where the probes go in and a quality new set of probes. Sometimes you can kind of restore them a little by cleaning with 99% alcohol followed with some Deoxit.

Ok, cleaned the probes and deoxed them, but the lowest I get with very high quality probes is .5 ohms, there is no way to 0 it. Whereas the cheaper tester Tais TA118A is dead 0 ohms when connecting the 2 probes together. It cost +- 40$ compared to the Fluke 87 V which had cost me over 500$. Probably need calibration and cleaning, but they're asking over 300$ CAD to do this at Fluke, not worth it.

[CapLeaker]

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

Ok, so I guess my old Fluke needs calibration - I used another (cheaper) multimeter and R3 measures .1 ohm...when I put my probes together it measures 0.0 ohms. So R3 is good.

The ground I use to make the measurements on the IC are the main caps ground which is on the primary side. When I put 0V for pin 1, it was just that that's what I recorded to later realize it's ground.

The optocoupler is maked EL 817 - this is the 3rd optocoupler, but I think they are all good.

Quite a mystery!

Probably doesn't need calibration, rather a good cleaning where the probes go in and a quality new set of probes. Sometimes you can kind of restore them a little by cleaning with 99% alcohol followed with some Deoxit.

[rddube]

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

rules that out then ..
what is connected to pin 4 ?

Pin 4 is connected to R9 a 28kohm resistor.

[petehall347]

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

Pin 5 is not connected to anything so probably not used?

rules that out then ..
what is connected to pin 4 ?

[rddube]

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

does it have an ntc connected to pin 5 ? if so what value is written on it ?
pin 5 needs to be over 1.05v or pwm is disabled

Pin 5 is not connected to anything so probably not used?

[rddube]

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

Ok, so I guess my old Fluke needs calibration - I used another (cheaper) multimeter and R3 measures .1 ohm...when I put my probes together it measures 0.0 ohms. So R3 is good.

The ground I use to make the measurements on the IC are the main caps ground which is on the primary side. When I put 0V for pin 1, it was just that that's what I recorded to later realize it's ground.

The optocoupler is maked EL 817 - this is the 3rd optocoupler, but I think they are all good.

Quite a mystery!

[CapLeaker]

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

What do you read by just touching the two probes together?

[petehall347]

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

Yes, you correctly noticed that the current resistor shows R3 1.1 Ohm, but it should be 0.18 Ohm, this could be a problem.

or meter error .

[stj]

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

just a thought.
when you take these readings, are you getting the ground from the input for the input-side and from the output for the output side?
because the 2 grounds arent linked.

[lotas]

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

From pin6 to ground is power resistor, what value, I see brown gray silver gold, and you measure 1.1R?

Yes, you correctly noticed that the current resistor shows R3 1.1 Ohm, but it should be 0.18 Ohm, this could be a problem.

[harp]

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

If you disconnect psu from mains, and remove secondary output diode and then feed adjustable 10-14v to output terminals, so that tl431 circuit is working, you can monitor opto transistor resistance (primary side) and confirm that switch on at 12v point. Set on 12v with trimpot 1K.

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Ok, so did the above test - removed secondary output diode, injected 12V on the output and took measurements of optocoupler resistance primary side:

No voltage applied (power off) - 3.191K ohms
10V applied - 1.086Mohms
12V applied - 1.086Mohms
13.3V applied 1.088Mohms

Strange, I was expect that resistance go down from initialy... What is optocoupler marked name?
So it seem the problem is on primary side, or transformer.

From pin6 to ground is power resistor, what value, I see brown gray silver gold, and you measure 1.1R?

And I notice one more thing... where is ground, you noted like GND or 0V... if ground isnt 0.000v that means that somewhere on board is short witch pull up a ground awhile. Is ground pulsating last digit-two also?

[petehall347]

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

does it have an ntc connected to pin 5 ? if so what value is written on it ?
pin 5 needs to be over 1.05v or pwm is disabled

[stj]

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

pin7 is fed by a diode - can you check it.

[rddube]

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

best i can think is drain power from main cap . mains power disconnected first of course .then measure resistances each pin reference pin 1 ground .

Pin 1 - Gnd -
Pin 2 - 0.656MΩ
Pin 3 - 1.487MΩ
Pin 4 - 28.09kΩ
Pin 5 - .915MΩ
Pin 6 - 1.1Ω
Pin 7 - 1.2MΩ charging
Pin 8 - 9.54kΩ

[petehall347]

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

best i can think is drain power from main cap . mains power disconnected first of course .then measure resistances each pin reference pin 1 ground .

[rddube]

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

i take it the supply voltage is stable at the main cap ? think this mentioned so ..
pin 6 you missed for some reason ..

Sorry pin 6 I had written down but did not put it in the list for some reason:

pin 6 - 0V