sanyo no back ligth

[tom66]

Re: sanyo no back ligth

Yes, he tested R322 which is the main fusible resistor in this instance.
The fault is probably on the IC which drives the MOSFETs.

[ealequi]

Re: sanyo no back ligth

which is that one? i still learning.

[selldoor]

Re: sanyo no back ligth

That datasheet for the transformer doesn't look like the correct part. It looks like a conventional 50/60 Hz transformer, not an SMPS one.

GOOD CATCH Tom - I am now fairly sure you are correct (again )
I have checked and re googled under the part number PFT24-35 It is even available on Digikey cant think why anyone would save it on a pdf with the part number of this transformer MP-130B. I thought it was a bit easy to find and it did look the same shape/pins etc and the 1500Vrms threw me .
The one on the board is probably proprietory and unobtainable.

Ealequi - have you tested the fusible resistors?

[tom66]

Re: sanyo no back ligth

That datasheet for the transformer doesn't look like the correct part. It looks like a conventional 50/60 Hz transformer, not an SMPS one.

[ealequi]

Re: sanyo no back ligth

thank for the advise

[selldoor]

Re: sanyo no back ligth

Dont do that - do resistance test only - did you read the datasheet
1500 Volts probably wont do your meter any good.

[ealequi]

Re: sanyo no back ligth

I am not easy to give-up

[ealequi]

Re: sanyo no back ligth

I am going to test the transformer to see if there is power going in and coming out

[selldoor]

Re: sanyo no back ligth

OK. please check the fusible resistor R322 that feed the B+ to the inverter transformer driving circuit.

You may as well check the other two fusible resistors at R332 .

I attach a datasheet for the transformer I am not sure what you can test on it
Start with the primaries - Power off - meter on 2000 ohms check and post result. Budm or Tom may be able to suggest further tests ( How to check the secondaries)

[selldoor]

Re: sanyo no back ligth

Off topic a bit - I have a question for Budm Or Tom66. On the bottom of the board (Pic post 70) Pan along the bottom edge t the midpoint hole then up slightly there are two points marked OVP 12v and OVP 5v - OVP means Over voltage protection? but are those actual components or what? Cant see anything to correspond on the top of the board.

[budm]

Re: sanyo no back ligth

OK. please check the fusible resistor R322 that feed the B+ to the inverter transformer driving circuit.

[lorins_core]

Re: sanyo no back ligth

Ok i Suggest. Would you try to Resolder. fist the Main Power Supply?. then Try if have no Luck. Try The secondary. they have a Old Solder lead at the Main Board. I Suggest Only. Good Luck Friend.

[MisterD]

Re: sanyo no back ligth

I see a lot of variances of this power supply board for your model, if you do order one BE VERY CAREFUL to get the part number off of the white bar code sticker and not the pc board itself, I see some on ebay and also some places on ebay repairing your board if you send it in. you can also check shopjimmy.com to see what they have.

[budm]

Re: sanyo no back ligth

That 1.3V can be the main board is not pulling high enough, there is voltage divider resistoirs that the 1K is feeding, that is why it will never be at 5V, 3.7V is more than enough to drive the transistor. That 1.3v reading was generated by the main board, since we cut that line open, all he now is the 5V feeding through the 1K resistor.
See post 86 for typical receiving circuit.
If he trace that BL_ON line, there will be a resistor connected to that pin.
Without the diagram of of the board, we cannot check for test points.

[MisterD]

Re: sanyo no back ligth

Before he added the resistor his readings were:
bl_on = 1.3
bl_dim = 3.2
5vstb = 5.v
Before making any changes BL_ON was only 1.3V, then after adding the resistor BL_ON was 3.7V and still no backlights. If there is a problem with the inverter board or bulbs why would it be at 1.3V. since the 1.3V would still be there and he is adding 5V through the 1K resistor I would think it would be higher than 3.7V, is it possible there is a shorted component on the inverter section or bad lamps pulling that voltage down?

[MisterD]

Re: sanyo no back ligth

deleted.

[budm]

Re: sanyo no back ligth

Well at this point we have verify that the backlights are not working not due to the main board problem but due to your bad power supply/inverter combo board problem or due to bad lamps.
We do not have the diagram to troubleshoot down to component level, but I want to make sure that you DID NOT EVEN SEE THE SCREEN FLASH for seconds? The problem is now down to either bad board or bad lamps, with one or two bad lamps I will expect to see the screen lights up for seconds then shutdown if the inverter board is OK, but if the inverter board is bad it may not even try to light up the screen at all, this is where you have to make the decision if you will want to try ordering the new power supply-inverter board to find out if it will fix the problem or not.

[ealequi]

Re: sanyo no back ligth

ok. i missing the backligth. i have video, sound led i green but no backligth.

[MisterD]

Re: sanyo no back ligth

The backlight (a white light ) can be seen through the holes in the metal chassis from behind with the back off the TV, the LED he is referring to is the little light on the front of the tv plastic case. Do you have that white light?

This is from your first posting and it sounds like the backlight is not working because you are using the flashlight method to see video.

"I have a sanyo dp42647 when i turn it on there is a black screen with sound. If i put a flashligth close to the screen i can see the video. Any idea?"

[ealequi]

Re: sanyo no back ligth

There is a misunderstanding. Is the back ligth went you able to see the video but is dark? That is what i have. I need the brite ligth wish i imagine that is the led. The tv still doing the same thing that make me come to the forum