Power suply doesn't work (DPS-214CP)

[NoN4me]

Hello,
I've got a TV wich power supply is a DPS-214CP (schematic attached), and the thing is that it doesn't power on. I dont even get stand by power.

IC901 (DDA010) has an VCC Votage between 10 and 18 Volts in a triangle wave. It's said in the IC901 datasheet that IC starts up when vcc reachs 18 volts, but in my case Drain pin never starts switching.

I have checked diodes resistors and caps but I can't find the problem.

Can anybody lend a hand?
Thank you in advance.

[petehall347]

Re: Power suply doesn't work (DPS-214CP)

is b+ good ?

[CapLeaker]

Re: Power suply doesn't work (DPS-214CP)

maybe a dead pwm. Wouldn't be the first time...

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

is b+ good ?

Yes, 320 volts

maybe a dead pwm. Wouldn't be the first time...

The pwm is that DDA010, isn't it? I have replaced it already. Nothing hapened.

[dskall]

Re: Power suply doesn't work (DPS-214CP)

optocoupler, feedback voltage?

[budm]

Re: Power suply doesn't work (DPS-214CP)

What did you use for the GND ref. point for your meter or scope when you make the Voltage measurement in that primary side of the circuit?

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

optocoupler, feedback voltage?

5 volts in FB pin

What did you use for the GND ref. point for your meter or scope when you make the Voltage measurement in that primary side of the circuit?

I put the aligator clip of the scope in the negative pin of the main capacitor.

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

Here you are the measures at the diferent points commented before.
B+, FB pin, IC Vcc (in this order).

[dick_barton]

Re: Power suply doesn't work (DPS-214CP)

VCC is initially supplied via the DDA010 internal current cell until it reaches a specific value after which it switches off. The IC should then start to drive the internal mosfet to switch T901 which will then maintain VCC through the winding (pins 9-10) of T901 which is rectified and connected to VCC and it's charging capacitor C904.

If the IC fails to drive T901 for whatever reason, then there is no secondary voltage to maintain VCC. The IC restarts and charges the VCC startup capacitor via it's internal startup circuit once again until it reaches VCCstartup threshold at which point the internal charge circuit switches off.

This I believe would explain the ramp that you see on VCC

VCC = 18V and internal charge circuit switches off
VCC = 10.5V and internal charge circuit switches on

Can you scope the Drain (pin 5) and check that the internal mosfet is switching transformer T901

I would check R903, D902, C903, C904, D903, Q901, R904, ZD901

Out of curiosity are you using an isolation transformer to power up the set or using a scope isolation probe?

[dskall]

Re: Power suply doesn't work (DPS-214CP)

Here is spec sheet for DDA010 http://www.datasheetspdf.com/datasheet/DDA010.html
Seems 5v feedback is to high but I am not good with specs so budm or someone can correct. And educate.

[budm]

Re: Power suply doesn't work (DPS-214CP)

The current sensing resistors on CS pin 3 are good?
If leave the scope on Drain pin 5 and nothing else hook up to the board then you apply AC to board, do you see any action at all on the Drain pin for seconds? The rectifier D950 in the cold side is good?

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

Can you scope the Drain (pin 5) and check that the internal mosfet is switching transformer T901

I would check R903, D902, C903, C904, D903, Q901, R904, ZD901

Out of curiosity are you using an isolation transformer to power up the set or using a scope isolation probe?

I have attached a screenshot of the drain pin.
Those components that you mentioned are OK.
About isolation I'm not using any of them, just being very careful avoiding touch the ground of the scope.

The current sensing resistors on CS pin 3 are good?
If leave the scope on Drain pin 5 and nothing else hook up to the board then you apply AC to board, do you see any action at all on the Drain pin for seconds? The rectifier D950 in the cold side is good?

Yes, current sensing reistors are OK and D950 is also OK.
I have atached a screenshot of the input pin of the IC902 as well as a screenshot of the behaviour of the drain pin when I apply AC to board.
D950 is also OK.

[dick_barton]

Re: Power suply doesn't work (DPS-214CP)

It's best practice to use an isolation transformer so that you don't accidentally give yourself a shock. Cheaper than a funeral.

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

Of course, I know, but I don't have an isolation transformer, I don't usually measure live areas.

[dick_barton]

Re: Power suply doesn't work (DPS-214CP)

So transformer T901 is not being switched.
IC902 (IN1) needs 1.8V peak or more and the output (FPO) I think would be around 7V

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

Well, I have to say thay in this case when I measure FPO with the scope I obtain a flat line in 0 volts but when I measure with a multimeter I obtain 5 volts. (I desoldered FPO pin to measure it)

[PeteS in CA]

Re: Power suply doesn't work (DPS-214CP)

Does the FB pin voltage of ~4.5-5V shut down the DDA010?

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

I don't know.

[dick_barton]

Re: Power suply doesn't work (DPS-214CP)

From the data sheet it looks like FPO is Low (0V) when IN1 is between 1.17v --> 1.28V
When IN1 => 1.28V then FPO goes High.

You cannot measure FPO with the pin disconnected since it's an an open Drain connection.
Datasheet post#15

[NoN4me]

Re: Power suply doesn't work (DPS-214CP)

Ok, that way, with the pin soldered I measure near 5 volts, same as I currently have at FB pin of DDA010.