Sharp LC-70SQ15 PWB DPS-206EP problem

[rabitbay]

Hi everyone

I have this problem with the PWB, it all begins with shade areas on the screen done by bad led strip, it worked for about 4 months until the tv goes off for it self, when try to power on again it just stay on for about 3 second and go off again, then throws a 1-1 blinking code, at that moment I thought "the strips just burn off" so I fully disassembled the tv and find out most of the led strips was burn. So I replaced de bad leds (almost 90) then I tested by groups of 4 by for leds for (I just have a 24v power supply) and every LED was tested and was OK.

Once I put on the strips and assembled the panel try to enter the adjustment procedure to reset the led error count, and find out this scenario:

Scenario 1: TV not turning on, not even the backlight, just solid white on center icon and solid green on main board and after about 30sec turn off for about 1 sec then solid again, and this repeats three times then throws 3-1 flash code (Initial communication error).

So I tried the CH Down and Vol+ and get solid white on icon and Main board solid Led green but nothing else, then Scenario 1.

So this what I tried:
All t-con flex cables disconnected + CH Down and Vol+: Scenario 1
All t-con flex cables disconnected + Adjustment Procedure : Scenario 1
T-Con disconnected from Main: 3-2 Flash code (similar to https://www.youtube.com/watch?v=jHjBjIaQzXc)
Voltages on L1 Anode connections With LED strip disconnected: 167.2V
Voltage on L1 Cathode connections With LED strip disconnected: 0.02V
Voltages on PD are almost perfect (verified with SpeedAdiction thread) except for a NC pin getting 2.5V this PIN is between 5v BUS and Dimmer
Just LED stripes connected + PNL_POW and PS_ON feeded: getting 167.2V on L1 but not lighting stripes.
When everything is connected I find out T-Con 12V are feeded, but after the first Flash on Scenario 1, no 12V are feed, T-TCON is turned off


There's something more, if I'm not wrong each of the 3 LED strip have 2 arrays of 32 series LED of 6V each (7030 Led) Isn't necessary at least 192v for power the entire Led strip?

Here's where I get stuck, any help would be appreciated

[R_J]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

Monitor the voltage on L1 pin4, This voltage needs to be measured when the tv is FIRST turned on, (when the voltage is boosted) If there is a fault, it will drop to 167v.

You can also check the voltage on the return pins,1,3 & 5, when the tv is first turned on, this is the return line and will likely be around 20v if the string is good and 0 volts if a string is open.

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

"Just LED stripes connected + PNL_POW and PS_ON feeded: getting 167.2V on L1 but not lighting stripes." You have done that without cable going to the main board, correct?
STB pin = BL-ON = Control Voltage (around 3V) to force on the backlights circuit.
PNL_POW is the control pin to turn on the switched PNL12V to run the run the T-CON board.

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

Monitor the voltage on L1 pin4, This voltage needs to be measured when the tv is FIRST turned on, (when the voltage is boosted) If there is a fault, it will drop to 167v.

You can also check the voltage on the return pins,1,3 & 5, when the tv is first turned on, this is the return line and will likely be around 20v if the string is good and 0 volts if a string is open.

I've attached the readings, in this model the Cathodes are connected to a common point, to a MOSFET that I checked worked properly, but something curios happens when I was checking this MOSFET... I accidentally touch the drain pin with the sink (grounded) and then the backlight was turned on!!
What's going on here?

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

"Just LED stripes connected + PNL_POW and PS_ON feeded: getting 167.2V on L1 but not lighting stripes." You have done that without cable going to the main board, correct?
STB pin = BL-ON = Control Voltage (around 3V) to force on the backlights circuit.
PNL_POW is the control pin to turn on the switched PNL12V to run the run the T-CON board.

That's correct, I did bridge from 5V Bus to STB pin and led strip connected and nothing happend, i't 3v mandatory?

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

That PWM controlled MOSFET Q7202 for maintaining the constant current through the LED strings (4) is driven by IC7201 LED driver IC. Do not short out the pin of the MOSFET otherwise you will force too much current through the LED strings and damage them.
Look up spec sheet for the IC7201 (BD9488?) to see how the circuit operates. Q7201 is for boost converter.
Sharp RUNTKB131WJQZ (DPS-206EP) Power Supply / LED Board
https://www.shopjimmy.com/sharp-runt...-led-board.htm

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

That's correct, I did bridge from 5V Bus to STB pin and led strip connected and nothing happend, i't 3v mandatory?

But did you disconnect the cable going to the main board first? It may also need the dimming control line too, STB >3V = Backlights circuit turned on.

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

But did you disconnect the cable going to the main board first? It may also need the dimming control line too, STB >3V = Backlights circuit turned on.

I did just cut and bridge 5v BUS to STB and Dimmer, and nothing happend while CHDown and Vol+ combination was used. Start to suspect on the OPAMP (LM258A) or the LED Driver (BD9488F)

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

I did just cut and bridge 5v BUS to STB and Dimmer, and nothing happend while CHDown and Vol+ combination was used. Start to suspect on the OPAMP (LM258A) or the LED Driver (BD9488F)

I do not undertsand, if you do not have cable between the power board and main board connected then there will be no power to run the main board which means using CHDown and Vol+ combination will do nothing.
If you did not remove the cable to the main board and force on the control pins, you can damage the main board.
Do not force on the power supply board without removing the cable to the main board first.
Did you look up the LED driver IC as suggested?
Start checking Voltages on the IC. The LED+ pins should be much higher than 167VDC when the LED power is working.

[nomoresonys]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

Don't you also need a resistor to ps-on as well when trying to jumpstart the powerboard without it connected to mainboard so resistor from ps-on and resistor from stb and maybe resistor from dimmer so those 3 resistors going to bu-5v, that might bring the backlights on, as mentioned no need to do ch- vol+ while mainboard is disconnected. PLUS MAKE SURE cable from powerboard to mainboard is unhooked.

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

At post 1 he said he jumps the PNL-PWR and PS-ON but now he said he jumps the STB and dim; so at this point I have no idea how pins he is forcing on, and yes 500 ~ 1K resistors should be used for each forced on pins. I also wonder what the rating of the replacement LED's are.

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

Don't you also need a resistor to ps-on as well when trying to jumpstart the powerboard without it connected to mainboard so resistor from ps-on and resistor from stb and maybe resistor from dimmer so those 3 resistors going to bu-5v, that might bring the backlights on, as mentioned no need to do ch- vol+ while mainboard is disconnected. PLUS MAKE SURE cable from powerboard to mainboard is unhooked.

Hi, thanks for the advice, so I made a test circuit, and yes, like budm said, I'm testing now with the unhooked main plug, and just LED plug connected

this is the circuit I made, just bypass every pin to a pot, just to be able to play with it, by default I set every pot to ~600 then tested with LED stipes conected but nothing

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

I do not undertsand, if you do not have cable between the power board and main board connected then there will be no power to run the main board which means using CHDown and Vol+ combination will do nothing.
If you did not remove the cable to the main board and force on the control pins, you can damage the main board.
Do not force on the power supply board without removing the cable to the main board first.
Did you look up the LED driver IC as suggested?
Start checking Voltages on the IC. The LED+ pins should be much higher than 167VDC when the LED power is working.

I tested every PIN after circuit test was plug in, I've attach voltages, including of the LED driver and the OPAMP, there I was doubting (I'm not electrician expert) but I have different voltages proporcions from one of the internal OPAMP1 and the OPAMP2 so what do you think, the chip seems ok?

The LED I used to replace was 7030

And just to clarify, as you said, I make the mistake once plugin in every harness and forcing on CHDown and Vol+, but now I'm just with the led stripes plugged and the test circuit (I made)

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

1) What DC Voltage do you have when measure between the two legs of the main filter cap? It should be around 380 ~ 400VDC if the PFC Voltage circuit is running with the present of the PS-ON.
2) What DC Voltage do you have on the LED+? It should be more then 200VDC if the LED boosted power supply is running when the BL-ON (STB) present.
3) 7030 LED is just the dimension of the LED body, nothing to do with the electrical spec of the LED, see PDF for example of the LG 7030 LED .

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

1) What DC Voltage do you have when measure between the two legs of the main filter cap? It should be around 380 ~ 400VDC if the PFC Voltage circuit is running with the present of the PS-ON.
2) What DC Voltage do you have on the LED+? It should be more then 200VDC if the LED boosted power supply is running when the BL-ON (STB) present.
3) 7030 LED is just the dimension of the LED body, nothing to do with the electrical spec of the LED, see PDF for example of the LG 7030 LED .

1) 418V on each of the three
2) I've attached a diagram as the voltages are different, but I have ~34.27v of return, and it's not more than 200v.
3) That's bad, sorry my ignorance, I suppose that, as the 7030 was on the serial number of the stripe (2012SSP70_64_7030_REVO_12012) what a shame, but it's 6v LED, if you need more LED spec info let me know to ask to the seller

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

You only have 167V on the LED+, it should be more than that if the LED Boosted Voltage is working.
It has 350VDC filter caps for reason.
Keep the probe on the LED+ then power up the board to see how high it jumps up to, black probe on circuit ground.

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

You only have 167V on the LED+, it should be more than that if the LED Boosted Voltage is working.
It has 350VDC filter caps for reason.
Keep the probe on the LED+ then power up the board to see how high it jumps up to, black probe on circuit ground.

The max value I could catch (In digital multimeter it's harder) was 268v, I did the test once the board was uncharged (seen ~.5v on LED+), otherwise I couldn't catch a peak.

That's interesting, what could be limiting the voltage to rise up?

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

After seeing the chip Led driver specs and comparing with my voltages reading, I realised I haven't voltage on the DIMOUT pin, and the UVLO (Under voltage lock out detection pin) It's receiving 4.26v so LED booster is called but it seems to not respond because has no voltage on DIMOUT pin.

As long as I reed and understood the datasheet, this driver has the condition of LED Open Protection Function if ISENSE < 0.1v (that's true I have 0v, look at attached images on old post) for about 4 cycles,will cause an abnormal state, which cause DIMOUT to GND Level.

So I could think that the peak (258v or so) is catched on the lapse of 4 cycles.

Conditions where LED Open Protection Function is masked:
CASE1. When PWM = L. ISENSE is less than 0.1V even in normally,
because DIMOUT = L.
CASE2. In the soft-start interval. ISENSE is less than 0.1V, because of the
insufficient output voltage Vout.

It could be a faulty MOSFET?
As long as I know the led strip was ok, I have checked it in groups of 4 by 4

[budm]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

The max value I could catch (In digital multimeter it's harder) was 268v, I did the test once the board was uncharged (seen ~.5v on LED+), otherwise I couldn't catch a peak.

That's interesting, what could be limiting the voltage to rise up?

It is not seeing so it goes into shutdown due to over Voltage condition so all you see is the 167VDC feeding Voltage to the boost converter circuit once it is in shutdown mode.
So just to be clear, right now when you power up the board you DO NOT see the backlights flash on for seconds, correct?
You are also seeing over 200V on all four LED + each time you power up the board, correct?
BTW, 418VDC on the main filter caps is too high, it should have cause the PFC circuit to go into shutdown. Main caps are only rated at 450VDC. Are the batteries for your meter good? Low meter's batteries will cause the reading to be higher than it should be.

[rabitbay]

Re: Sharp LC-70SQ15 PWB DPS-206EP problem

So just to be clear, right now when you power up the board you DO NOT see the backlights flash on for seconds, correct?

Not even a flick

You are also seeing over 200V on all four LED + each time you power up the board, correct?

Correct, BTW when I did the test for the first time this morning (for double check) I got around 300v reading, then over 200v

BTW, 418VDC on the main filter caps is too high, it should have cause the PFC circuit to go into shutdown. Main caps are only rated at 450VDC. Are the batteries for your meter good? Low meter's batteries will cause the reading to be higher than it should be.

Just to avoid any bad reading, I just changed my multimeter batteries for new ones this morning and double checked, I did had the same readings.