sanyo

[dejesus]

this are the pic for the Sanyo dp52449 no backlight

[dejesus]

Re: sanyo

It been sometime I don't ad a tread, but this time I need some help. I pick this tv real cheap. It has sound and if I put a flash light I can see the video, but there is not backlight. I am getting the 5 and the 12 volt, still no back light. I connect the 5v to the bl_on with a 1k resistor but nothing happen. Can someone tell me how can I get the backlight on? Posting some pics.

[Mrx3750]

Re: sanyo

Hello there. Do you have a multimeter, and can you start testing voltages?

[dejesus]

Re: sanyo

yes

[budm]

Re: sanyo

OK, when you try to force on the BL_ON pin, you will have to disconnect that wire which goes back to the main board otherwise if the BL_ON is being held to ground by the main board it will not allow you to take that pin HIGH with 1K resistor.
Second: you need to remove that big aluminum plate off the power supply/inverter board so we can see what are under the plate. You will need to check the DC voltage RIGHT AT THE TWO LEGS of that large 450V filter cap, it should have about 160VDC when TV is plug in and it should go up to about 380~400VDC when you turn the TV on. Be real careful not to touch anything with your hand since you will be working in the HOT (deadly side) of the circuit.
By the way, what DC voltage do you get at BL_ON pin when TV is OFF when when TV is ON?

[dejesus]

Re: sanyo

cn7 nc=0 bl_adj=0 bl_on=0 gnd, stb5v= 5.0v

cn2 line on/off=0 15v=15v 15v=15v gn,gn,12v=12v 12v=12v 12v=12v 12v=12v gn,gn,d5v= 5.v gn ps on/off= 4.5v

cn3 ldp1 =3.3v ldp1= 3.3v gn, gn, gn, lcf=0 12v= 12v

[budm]

Re: sanyo

Hmm, the Line ON/OFF does not make sense, does it change state when TV is OFF and when TV is ON? I also expect some voltage at BL_ADJ (Backlights brightness).

[dejesus]

Re: sanyo

Budm, hello. What a did is that I cut the wire from the bl_on long enough to put it back together later on.

[dejesus]

Re: sanyo

Retested line on/off, no power with tv off or on. BL_ADJ no power with tv on, .27v with tv off.

[budm]

Re: sanyo

OK, this power supply board has PFC Voltage booster, check the voltage right at the two legs of the 400vdc brown caps when TV is off and when TV is ON. I also need to see the whole top side shot of the board.

[dejesus]

Re: sanyo

are you referring to the 400v capacitor?

[budm]

Re: sanyo

Yes, the two brown one laying side way.

[dejesus]

Re: sanyo

Voltage on both cap is 168 v went off and 349v went on

[budm]

Re: sanyo

That is good, the PFC is working OK.
Above the two caps is the High Voltage Inverter transformer, to the right of it there are two MOSFETs, and two Diode mounted on the heat sink, they are for driving the inverter transformer. We need to find out if we are getting the 349V to feed that circuit or not, so please post the WHOLE toP side of the board and the bottom side, then 1/4 section or smaller of the bottom side. I am looking for some kind of fuse or fusible resistor that the 348V feeds in to it and the out put side of the fuse then feed the 348v to the MOSFETs.

[budm]

Re: sanyo

One thing that is bugging me right now is that the main board is not sending out the BL_ON or the BL_Adj signal, plus you cannot turn on the backlights using the resistor, I hope that you do not have TWO probelms on both boards.
I like to try one more thing is to cut the BL_ADJ line and leave it without anything connected to it to see what happen when you put 1k between BL_ON and 5v.

[dejesus]

Re: sanyo

how are this?

[dejesus]

Re: sanyo

ok I will try that

[dejesus]

Re: sanyo

I did it and nothing happen. With the bl_on and bl_adj cut and a resistor on 5v to bl_on getting 4v but nothing happen not even a blink.

[budm]

Re: sanyo

OK, put 1k between BL_ADJ AND 5V also and see what happen.

[dejesus]

Re: sanyo

Did it,nothing happen