Sony Bravia KDL-46EX640 no power

[bullwinkle]

My 2 year old Sony Bravia KDL-46EX640 LED TV does not have any power at all. No RED LED standby indicator in the front panel can be seen. In short, deadset.

My first step is to check the AC power cord and it turns out OK. Now I check fuses at the power supply board. All are OK. What's next?

Any help would be much appreciated. Please help.

[budm]

Re: Sony Bravia KDL-46EX640 no power

Post good clear pictures of the back side so we can see how the boards are connected together will be a good start.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

Here are some pics as requested.

[tibimakai]

Re: Sony Bravia KDL-46EX640 no power

I'm in the same situation with a 55EX720. I don't even have standby.
At the moment I'm waiting for a voltage regulator to arrive. On mine(yours may be different) I have 6 pin voltage regulator at the output of the standby transformer, which shows 4.27V input and output, which is not good, because the output should be 3.3V.
I'm hoping, that it didn't mess up the mainboard.

[budm]

Re: Sony Bravia KDL-46EX640 no power

OK, measure the DC voltage right at the two legs of the main filter cap (big black cap laying on its side) C6530. You are working on the HOT side of the circuit so do not touch anything with your hands or body, plug the TV into GFI outlet will be a good idea.
http://www.shopjimmy.com/media/catal...4-11-top_1.jpg

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

@ budm:

Its 393.4 Volts DC.

[budm]

Re: Sony Bravia KDL-46EX640 no power

If that is the case, then the main board is sending out the PS_ON to turn on the PFC voltage booster. Turn the TV power switch to off, then the voltage on the cap should drop down to around 160~170VDC. Your meter is good, right?

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

If that is the case, then the main board is sending out the PS_ON to turn on the PFC voltage booster. Turn the TV power switch to off, then the voltage on the cap should drop down to around 160~170VDC. Your meter is good, right?

Its a Fluke 79III True RMS Multimeter. But when I take the DC voltage, I simply plugged in to AC outlet and measure it across the big capacitor which is 393.4Vdc. I did not use any power switch since I can't see any RED LED standby indicator on the front panel.

[sugar_ray]

Re: Sony Bravia KDL-46EX640 no power

98% of the zero power issues I have encountered always seem to lead to a bad power supply board. Even after testing components that seemed ok. Just had a toshiba this weekend with the same issue your having. No standby, no front light, wouldn't respond to remote or side buttons. Just dead!! With meter I could tell the ps board was getting power but that's as far as it was going. No output. Ceramic fuse was fine as well. In most cases this will be a bad ps board. You'll just have to decide if you want to hunt down components or just replace the supply board itself. Rare occasions it can be the main board, but from experience, a bad main will still allow a standby light.

Here was the toshiba I was referring to. Replaced ps, and it lives!! Best of luck

https://www.youtube.com/watch?v=Bk9a...ature=youtu.be

[cliff_hootarski]

Re: Sony Bravia KDL-46EX640 no power

In your second picture, do you see any burn marks on the mainboard near the connectors
at the top right of the board? Hard to tell in your pictures.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

I'm in the same situation with a 55EX720. I don't even have standby.
At the moment I'm waiting for a voltage regulator to arrive. On mine(yours may be different) I have 6 pin voltage regulator at the output of the standby transformer, which shows 4.27V input and output, which is not good, because the output should be 3.3V.
I'm hoping, that it didn't mess up the mainboard.

Please update us soon.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

In your second picture, do you see any burn marks on the mainboard near the connectors
at the top right of the board? Hard to tell in your pictures.

Checked both the power supply board and the mainboard using magnifying lens. All clean. No burnt marks or components.

[tibimakai]

Re: Sony Bravia KDL-46EX640 no power

What do you get at D6201? That should be the diode after the standby transformer. Use the TV for ground when measuring.
Monday I should get the part.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

If that is the case, then the main board is sending out the PS_ON to turn on the PFC voltage booster. Turn the TV power switch to off, then the voltage on the cap should drop down to around 160~170VDC. Your meter is good, right?

Turned the switch to OFF but still the voltage present across the big filter capacitor is 393.4Vdc.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

What do you get at D6201? That should be the diode after the standby transformer. Use the TV for ground when measuring.
Monday I should get the part.

D6201 voltage is 3.327Vdc.

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

Other voltage infos:

D6303: Anode side: 374.4 Vdc and Cathode side: 420 Vdc
D6308: 14.41 Vdc
D6307: 13.98 Vdc

IC6301 (MIP2H2):

Pin 1: 5.74 Vdc
Pin 2: 1.632 Vdc
Pin 3: 0V
Pin 4: 14.41 Vdc
Pin 5: 374.5 Vdc
Pin 6: - - -
Pin 7: 0V
Pin 8: 0V

Any ideas?

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

These components are also taken out and measured:

C6308: 4.7uF/50V (measured = 4.8uF / ESR = 3.3 ohms)
R6301: 10 Ohms (measured: 10.3 Ohms)
R6302: 100KOhms (measured: 99.1 KOhms)
C6311: 2.2uF / 50V (measured: 2.38uF / ESR = 5.8 Ohms)
C6310: 100 uF/50V (measured: 110.9 uF / ESR = 0.65 Ohm)
C6524: 10uF/50V (measured: 10.5uF / ESR: 2.3 Ohms)

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

D6303: Anode = 374.4 Vdc / Cathode = 420Vdc
D6308 = 14.41 Vdc
D6307 = 13.98 Vdc

Im wondering if the ESR values stated are beyond their normal values. Do I have to replace those caps? Any inputs?

[Ltank]

Re: Sony Bravia KDL-46EX640 no power

The Tv PS turns on as soon as the set is plugged in and the PS turns on? Can it still be turned off and back on? The MB gives the PS_On all the time? Normally if there is no standby voltage the set will not turn on at all. Strange

[bullwinkle]

Re: Sony Bravia KDL-46EX640 no power

The Tv PS turns on as soon as the set is plugged in and the PS turns on? Can it still be turned off and back on? The MB gives the PS_On all the time? Normally if there is no standby voltage the set will not turn on at all. Strange

When I plug the unit to the wall outlet, i didnt see any RED LED Standby Indicator at the front panel. But when I trace the voltage starting the AC side, voltage is present, DC across the big filter capacitor is also present and in normal value.

BUT, even if I press the POWER SWITCH located at the side of the unit, the DC voltage across the big filter capacitor remains the same. No changes at all. Does this mean a bad power switch?