Philips 55PFL3907/F7 Sound and Backlight, No Video

[tumoheat]

Hello, I have Philips 55PFL3907/F7 LCD TV with sound and backlight (I can see the light from behind), but no video. I replaced the TCon board and still nothing. Not sure what to try next. I thought it could be the Inverter boards but the tech at ShopJimmy didn't think so. Any guidance would be greatly appreciated.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Try unplugging ribbon cables from t-con to panel one at a time and see if you get picture

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Thanks for replying. I unplugged the one ribbon cable and got a 1/2 white 1/2 black screen. The white side was where I disconnected the cable. Repeated the process with the other cable and go the same thing, with the white side of the screen being on the side of the disconnected cable.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

So happens I have same model with same problem. I have a frc board between the t-con and main board and was getting no data out so I replaced and still have same problem. Unplugging ribbon cables I get same results as you. I know this is not much help. Thinking a main board at this point.

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Looking at he main board I don't see any bad capacitors, and I tested the fuse. Not sure where to look. I tried finding the SM online but no luck.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Manual: https://www.electronica-pt.com/esque...ileinfo/26605/

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Thank you.

[maxvalutech]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Would seem like a main board problem. Have you tried input from AV or HDMI. Then possible Eeprom update. Is the tcon getting its voltage. LVDS intact both ends. Just some thoughts.

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

maxvaluetech, I hooked up a DVD player and got sound but no picture. I'll have to check the other things when I get home. Thanks for the reply and suggestions.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

From what op is reporting. He's got same problem I have. From my testing I believe I have a good panel, good t-con, good power supply. This tv has a separate frc board. With oscilloscope I get data going into frc but not coming out. Pressing menu button changes waveform. Main ic on frc board gets warm. Checked voltages on frc all seem good. Replaced frc board same problem. I am thinking main board needs to send reset or some signal to frc to enable

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Does your setup look like this? See attachment.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

That's it. Parts seem a little hard to find. You've changed t-con. I've changed the board above the main board. Power board is good. Leaves main board

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Main board, correct?

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Board to right with metal shield over it

[tumoheat]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

This one, correct? I'll start going through the SM and see what I can find on it.

[kdh2012]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

That's it. Parts seem a little hard to find. You've changed t-con. I've changed the board above the main board. Power board is good. Leaves main board

Anybody ever verify that the main board was the problem?

I also changed the FRC board because it has working inputs, but no output at all. If it is the fault of the main board, it must be something with the SDA, SCL or, Uart signals. Everything else looks good.

It's hard to accept that the main board is bad when it is doing so many things correctly??

So, anyone ever fix theirs with this precise problem? TIA!

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Op replaced t-con. I have replaced frc. I have not gone further. I think that frc needs an enable signal from mainboard to turn on. My best guess

[kdh2012]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Op replaced t-con. I have replaced frc. I have not gone further. I think that frc needs an enable signal from mainboard to turn on. My best guess

Thanks for responding on this. I believe that you are correct about needing an enable. But, I think it is a complicated handshaking sort of enable.

Almost like the main board forgot that it has an FRC board and is just outputting the data and clock signals that a T-con board would use.

[dskall]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Frc chip gets warm and data going in. Not likely bad frc since two have been changed. So would think mainboard is the problem. Find enable pin on frc and check for signal

[Davi.p]

Re: Philips 55PFL3907/F7 Sound and Backlight, No Video

Hi, i don't have a scope, which signal do you measure? differential one? what type of wave do you see and with which frequency range? How do you think that a bad comm signal main<>frc can result to lvds data sent? power supply tensions generated on frc how do you have checked, with the help of schematic? I have repaired an frc board (Philips), there is a switch transistor to feed power to the panel, it was broken togheter with a linear regulator, are you sure you have 12v on the tcon? Thinking of the flat cable test it seems to be good, but in this case is serial comm between frc<>tcon that don't work (but this can still belong to mainboard). I think that a SM reset, and eventually a SW reflash+SM reset is a next step. BYE