Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

[Martin_Silberkuhl]

Hi there,

I've a problem with a Sharp TV.

If I plug-in, only the turned "V" lights blue steadily. I cannot switch into stand-by, not with the power sensor button on the front, not with the remote control. Remote control ist working because if I press a button the "V" starts to flicker. If I connect my laptop via HDMI, no picture and no sound appears.

Following actions I did, but had no effect:

- hold VOL down and INPUT buttons at the same time, then press POWER

- measure all voltages on the right connector of the psu
>result: can measure all voltages with a dvm, except PS_ON, BL_ON (0V), PWM1 and DIM, because not knowing what to expect)

- measure all voltages on the top connector which supply the backround LEDs
>result: no voltages between LED+ and LED-, but if I disconnect and drive the LEDs with an external psu, the LEDs are working

- measuring all diodes on the psu
>result: all diodes are OK

- looking on all capacitors
>result: seems to be OK, nothing is bloated

Any idea?

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

A good start is to give the voltages on the connector. The label for the pinout is at the top of the photo.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

OK, here we go:

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

You have no backlight or DIM voltages so the backlights won't come one. You should have sound and be able to see a picture using a bright light source (torch) shone onto the screen and looking carefully.

If you disconnect the main board and power up, do the backlights come on. If not I would with the mainboard still disconnected, jumper the 5V standby to BL_On using a 1K resistor and a second 1K resistor to jumper 5V standby to PS_ON and see if the backlights then come on.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

First issue I can test tomorrow.

Second issue "jumper...." I've done (see photo).
After jumpering I can measure 5V on BL_ON and PS_ON, but no effect, so no
backlight.
Also the voltages on LED1+/LED1-, LED2+/LED2-,... are 0V.

Further suggestions?

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

What value do those resistors (above photo) measure with your meter?

When you initially power on and come out of standby what voltage do you have on the led connectors. Initially it may peak and then drop suddenly.
If no voltage then with the power off, check all the diodes with your meter set to diode mode.

Can you post a picture of the underside of the power supply.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Both 1kOhm, as you suggest.

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

The colours in the photo look like brown, grey, green, black, silver

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

When you initially power on and come out of standby what voltage do you have on the led connectors? Initially it may peak and then drop suddenly.

0V


If no voltage then with the power off, check all the diodes with your meter set to diode mode.

All diodes have about 0,46V forward voltage, except the 1N... . They have about 0,6V (that's normal).
D402 and D401 have 0,2V and D207 0,3V.

Can you post a picture of the underside of the power supply.

Is attached

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

OK, the value of resister is brown, black, green, brown, brown -> 1050 Ohm

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

What are the IC numbers as given on the IC's

[budm]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

When you initially power on and come out of standby what voltage do you have on the led connectors? Initially it may peak and then drop suddenly.

0V


If no voltage then with the power off, check all the diodes with your meter set to diode mode.

All diodes have about 0,46V forward voltage, except the 1N... . They have about 0,6V (that's normal).
D402 and D401 have 0,2V and D207 0,3V.

Can you post a picture of the underside of the power supply.

Is attached

Are you saying you have 0V at the LED+ PIN of the LED connector with ref to the chassis GND? Please clarify.
What DCV do you get by measuring between the two legs of cap C901?

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hey Dick,

the ICs U901A and U901B are both BD9483F (White LED Driver for large LCD
Panels - DCDC Converter type).

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hey Budm,

I measured the 0V between LED+ and LED-, not with ref to the chassis GND.

The DCV between the two legs of cap C901 is +90V.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hey Dick,

You should have sound and be able to see a picture using a bright light source (torch) shone onto the screen and looking carefully.

I tested it in the morning and I have no sound and no picture, also not using the torch.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hi there,

I really don't know, but because I can't switch the tv in stand-by I suppose the failure on the main-board. But let's stay in this systematically mode.

[budm]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hey Budm,

I measured the 0V between LED+ and LED-, not with ref to the chassis GND.

The DCV between the two legs of cap C901 is +90V.

You need to use chassis GND.
That 90V is the Voltage for feeding the Voltage Boost converter circuit to supply the Voltage to run the backlights LEDs.
You also need to do this test:
1) Turn the TV off.
2) Leave the DCV meter BLACK PROBE on the chassis, and Red probe on the LED+
3) Keep an eye on the TV and see how high the Voltage goes up to and then wait about 5 seconds to see if it goes back down to 90V.

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hi there,

I really don't know, but because I can't switch the tv in stand-by I suppose the failure on the main-board. But let's stay in this systematically mode.

Quite true i was forgetting that the tests were with mainboard disconnected.


What voltage do you have on Pin1 of the two IC's BD9483. The data sheets says between 11V to 35V This is with the jumper resistors in place as described in an earlier post.

[Martin_Silberkuhl]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

Hello guys,

hope you had a good weekend. The following things I have done in the morning:

@budm
You need to use chassis GND.
That 90V is the Voltage for feeding the Voltage Boost converter circuit to supply the Voltage to run the backlights LEDs.
You also need to do this test:
1) Turn the TV off.
2) Leave the DCV meter BLACK PROBE on the chassis, and Red probe on the LED+
3) Keep an eye on the TV and see how high the Voltage goes up to and then wait about 5 seconds to see if it goes back down to 90V.

I had done all three steps. When I switch on the TV, the voltage goes to exactly 90V and stays continuously.

@dick
Quite true i was forgetting that the tests were with mainboard disconnected.

You did not forget.


What voltage do you have on Pin1 of the two IC's BD9483. The data sheets says between 11V to 35V This is with the jumper resistors in place as described in an earlier post.

I measured 12,12V on both IC's Pin 1.

[dick_barton]

Re: Sharp Aquos LC-60LE652E - Blank screen, no sound, steady blue LED

12V is within the operating voltage range for those IC's
What voltage do you have on Pin 2 of each of them which should be >2V

I would check all the mosfets/diodes around those IC's. The 4 above and the 4 below the IC's