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

[Martin_Silberkuhl]

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

Hey dick,

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 measure +4,68V

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

see attachement

I'm not realy sure, if the mosfet's are defect, but normally there should be overload between Source and Gate, isn't it?

[dick_barton]

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

That voltage appears to be correct. So you have the supply voltage and the STB voltage (On/OFF) for both IC's but no boosted LED voltages (117.8V)
It would be unusual to find that both IC's are failing to boost the voltage needed to drive the leds.

Out of curiosity what voltages do you have on pin 23 (Reg90) which should be 9.0V and pin 12 (FailB) which should be at a High level.

MDHT4N20Y & MDD7N20C
Check between the Drain and Source, set powered off and with your meter in diode mode and you should see a diode reading one way and open circuit when you swap your meter probes around. There should be no short circuit between any of the pins of the mosfets.

[Martin_Silberkuhl]

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

Hey dick,

MDHT4N20Y & MDD7N20C
Check between the Drain and Source, set powered off and with your meter in diode mode and you should see a diode reading one way and open circuit when you swap your meter probes around. There should be no short circuit between any of the pins of the mosfets.

As I've already measured in one way 0,56V, the other way "open circuit" and no short circuit.

[dick_barton]

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

With your meter set to min/max to try and catch any peak voltage you have at switch on at the following components.
D901A
repeat
D901B
repeat
D902A
repeat
D902B

[budm]

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

You have 4 boost converter circuits, so did you do the test on each one of the LED+ four times? I cannot see how both LCD Controllers (1 IC with 2 boost converters) failed at the same time. Some thing that is common to all four circuits has failed if all 4 boost converters are dead.

[dick_barton]

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

I'm not realy sure, if the mosfet's are defect, but normally there should be overload between Source and Gate, isn't it?

Missed this tabled.
Testing in circuit can give those readings but you have no short circuits and D-S check out OK for each of them so they look fine.

What part number of the small 8 pin IC alongside the led driver chips?

[Martin_Silberkuhl]

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

@dick
That voltage appears to be correct. So you have the supply voltage and the STB voltage (On/OFF) for both IC's but no boosted LED voltages (117.8V)
It would be unusual to find that both IC's are failing to boost the voltage needed to drive the leds.

Out of curiosity what voltages do you have on pin 23 (Reg90) which should be 9.0V and pin 12 (FailB) which should be at a High level.

pin 23: 0V
pin 12: 0V

on both IC's U901A, U901B


With your meter set to min/max to try and catch any peak voltage you have at switch on at the following components.
D901A
repeat
D901B
repeat
D902A
repeat
D902B

D901A: 89,1V max.
D901B: 89,1V max.
D902A: 89,4V max.
D902B: 89,2V max.

What part number of the small 8 pin IC alongside the led driver chips?

AS358A

@budm

You have 4 boost converter circuits, so did you do the test on each one of the LED+ four times?

Yes, I did

[dick_barton]

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

With Reg90 at 0V this disables the Gate1 & 2 drives and also Dimout1 & 2 drives. So something is switching off the Reg90 supply. What voltage is on UVLO (Pin 17).

Unfortunately without the power supply schematic I don't know what the AS358 function within the circuit is.

[Martin_Silberkuhl]

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

With Reg90 at 0V this disables the Gate1 & 2 drives and also Dimout1 & 2 drives. So something is switching off the Reg90 supply. What voltage is on UVLO (Pin 17).


Pin 17: +5,66V

[dick_barton]

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

I find the data sheet confusing but I think it says that VCCUVL should be >7.0V and that the IC shuts down when VCCUVL <6.7V

[Martin_Silberkuhl]

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

I think the detection condition table is more meaningful.
Reading it, I think we have no Problem.

btw. - I measured the PWM1-Signal with my Oszilloscope, which should come from the Mainboard, but no Signal. So as I stated earlier, I think the failure is on the Mainboard.

What do you think and do we have a possibility to search on that board?

[dick_barton]

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

Could you try and jumper PWM1 & also PWM2 of one of the IC's to 5V using resistors and see if that clears the fault condition for that IC. Again with the mainboard disconnected and the other jumpers in place.
Data sheet does say PWMx = H; 2.0V to 5.5V

[budm]

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

What DCV do you have on pin 2 (STB: IC ON/OFF) of both LED driver ICs BD9483?

[dick_barton]

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

What DCV do you have on pin 2 (STB: IC ON/OFF) of both LED driver ICs BD9483?

In an earlier post (#21) it was given as 4.68V on each

[budm]

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

In an earlier post (#21) it was given as 4.68V on each

Ahh, I missed that one, thanks.

[Martin_Silberkuhl]

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

Hey dick,

Could you try and jumper PWM1 & also PWM2 of one of the IC's to 5V using resistors and see if that clears the fault condition for that IC. Again with the mainboard disconnected and the other jumpers in place.
Data sheet does say PWMx = H; 2.0V to 5.5V

OK, I connect my frequency generator to PWM1 of the connector, comming from mainboard + the other jumper in place.

Settings are: puls-signal, f=10kHz, V=5V

And as I switch on, the LED-stripes are lightning

So now we can definitely say, that the PWM1-signal is missing from the mainboard.

What do you think? Is it possible to search and find the failure, or do I have to buy a new mainboard?

[dick_barton]

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

This was an interesting piece of troubleshooting. It does appear as though you were correct and that without PWMx signals the Led Drivers stay latched off. If driving them externally brings them on then that rules out the Led Driver IC's or the leds as being at fault.

It does looks very much as though your diagnosis that the mainboard is at fault is correct.

[dick_barton]

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

Is the third picture in post #1 of the mainboard the mainboard in your TV. It looks as though it has been cooked in the oven. The plastic SCART has been melted.
This would suggest that someone may have tried to reflow the large BGA chip, IC3301 which would suggest there has been a previous attempt on repairing this mainboard.

[Martin_Silberkuhl]

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

yes dick, it was me.

With BGAs on your board, sometimes it could be a possibility to repair, by heating it. But I had no success and the connectors were damaged (but no problem for me).

Other idea: Do you know if there is an extra power-preparation on the mainboard to supply the ICs?

[dick_barton]

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

I am not sure of what you are asking.

If the set is for yourself then you could use a NE555 timer as a PWM to control the PWMx input and run it from a 5V supply. This may be worth while if everything else worked on the set.

http://www.electroschematics.com/583...ator-with-555/