PSU Liteon PA-3241-02A1 don´t work

[fpsousa]

Hi,
I have this psu and the symptom is: don´t has any out (12V and 24V); when I turn on in bulb series the 60W lamp lights one time (caps charging), then goes almost turn off and then come 4 or 5 fast flashes and finally turn off. Nothing comes out. Connect directly to 220 V stays all the same.
Can be the caps on secondary?
I´ve injected 12V on the 12v and 24V rails with a power supply, all seems correctly - caps charge and no extra consummation.
What could be?
Tanks

[momaka]

Re: PSU Liteon PA-3241-02A1 don´t work

Sounds like a bad "start-up" electrolytic cap. Post some pictures of the inside of the PSU so we can see.

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

Ok, I take some pictures. One cap on secondary is out because I'm take measure of capacitance and esr value.

[momaka]

Re: PSU Liteon PA-3241-02A1 don´t work

Good pictures, thank you.
Try first changing the two small "Jackon" electrolytic capacitors (black with gold letters). I think one of them is C054. Those are likely "start-up" caps I was talking about.

when I turn on in bulb series the 60W lamp lights one time (caps charging), then goes almost turn off and then come 4 or 5 fast flashes and finally turn off.

It probably does that because this PSU has active power-factor correction (APFC) circuit.

What's the part number of the IC on the primary side?

[mockingbird]

Re: PSU Liteon PA-3241-02A1 don´t work

I would change the caps that are squared in red...



Also, what's up with C205? Why was it removed?

[Stefan Payne]

Re: PSU Liteon PA-3241-02A1 don´t work

What's the part number of the IC on the primary side?

http://www.nxp.com/products/power_ma.../TEA1750T.html

Integrated PFC and Flyback controller.

From the layout I'd guessed it's an LLC-Resonant Mode Converter but according to the specsheet of the primary controller it isn't...

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

Hi, momaka, tank you.
I´ll change the caps you mencioned.
The IC is TEA1750T.

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

Hi, mockinbird, tank you.
C 205 is removed because i´m take measure is ESR (but is good).
But, i´ll take your advice and i´ll change them all.

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

I´ve replaced all the caps but don´t work.
I´ve checked the ESR from the new caps and compare with the old ones and they have more ESR but more capacity. is it possible?
Well, I've measured the Mosfet switching of primary and is ok.
Next I've measure the voltages at TEA1750T and on VCC pin it oscillating 18V-21V, and on PC300 and 301 there is any voltage, so I think is this chip the problem.
I´ll go put a new one and see what happens.

[momaka]

Re: PSU Liteon PA-3241-02A1 don´t work

Next I've measure the voltages at TEA1750T and on VCC pin it oscillating 18V-21V, and on PC300 and 301 there is any voltage, so I think is this chip the problem.
I´ll go put a new one and see what happens.

Let us know what happens. Curious to see if this is the problem is here. The oscillating voltage on the Vcc pin of the TEA1750T PWM/PFC controller is definitely indicating some kind of a fault condition that is likely making the PSU cycle ON and OFF continuously. Could be a short-circuit or overload on the secondary too. Check MOSFET Q201 on the secondary side as well as the MOSFET next to it. They are mounted on a small heatsink. Also check the TO-252 MOSFETs/diodes on the solder side as well.

Finally, *carefully* check the voltage across the main capacitor on the primary side with the PSU plugged in. I think it should be close to 380 V DC or more due to APFC.

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

Hi, again
Well I solved this problem and want to share with you.
After replace the IC TEA1750T, it stays the same.
So I've go again to research bad components at the secondary side and discovered a smd mosfet with leakage between source and drain; this mosfet is marked S72 (=2N7002) and connects pin 7 from TEA1762T and optoelectronic PC300.
So this inhibits the primary to start, I think.
Tank you all for your advices and hope this case can help you too.

[fpsousa]

Re: PSU Liteon PA-3241-02A1 don´t work

with some pics

[momaka]

Re: PSU Liteon PA-3241-02A1 don´t work

Nice work! Good to hear you got it fixed.
Those tiny SMD MOSFETs can be a pain to find when they go bad. Looks like yours darkened the PCB a little from all of the heat it produced.