Arquos 70LE640u dead

[paulstef]

Just wanted to know if there are any known issues with this TV.

It doesn't turn on. Front LED flashes long then short indicating an LED or inverter failure according to SM.

Primary main voltage stays at 170V, no boost. LED transformer is not driven. How the mainboard knows there is a inverter fault if it doesn't even try to drive it I don't know...yet.

Board is RUNTKA933WJN6.

I have 5V nothing else...

[paulstef]

Re: Arquos 70LE640u dead

The PFC can be made working (goes up to 405V) by shorting PS_ON to BU5V on connector PD.

Unfortunately there are som many signals it's hard to say which one would control the LEDs. There are DIMMER, PWM1, PWM2, PNL12V, OFL, PNL_POW.

In the SM it says:
"ERR_PNL: failure(H). Inverter/Lamp error is detected.
Note that after five detection counts, the lamp cannot be
activated except in the adjustment process mode.
Accumulated counts are cleared to 0 by the setting in the
LAMP ERROR RESET on the adjustment process mode."

Now, how would one get into adjustment process mode if there is no backlight????

[tom66]

Re: Arquos 70LE640u dead

Adjustment process mode means the service menu; it's activated by holding keys on the TV (check service manual for further details) usually VOL- and CH- or VOL- and INPUT.

[paulstef]

Re: Arquos 70LE640u dead

Adjustment process mode means the service menu; it's activated by holding keys on the TV (check service manual for further details) usually VOL- and CH- or VOL- and INPUT.

Thanks Tom, but what I don't understand is they say in order to reset the backlight fault counter I would need to access the service menu. When the counter is higher than 5 the backlight would not be activated (PS_ON stays low).

Does this make any sense? How do they want us to reset the counter if the backlight is always off? Seems like a contradiction.

http://elektrotanya.com/sharp_lc-52-.../download.html

[paulstef]

Re: Arquos 70LE640u dead

How do I test those backlights? Just applying a high enough voltage (with current limit)?

There are three sections. How much voltage would I possibly need? The two main secondary voltage caps have a rating of 200V and the other 3 electrolytic caps a rating of 350V...

[tom66]

Re: Arquos 70LE640u dead

Entering the Adjustment mode temporarily inhibits the backlight counter disable. The backlight should come on, if it is not faulty.

[paulstef]

Re: Arquos 70LE640u dead

How do I test those backlights? Just applying a high enough voltage (with current limit)?

There are three sections. How much voltage would I possibly need? The two main secondary voltage caps have a rating of 200V and the other 3 electrolytic caps a rating of 350V...

[tom66]

Re: Arquos 70LE640u dead

Very hard to tell. It depends on the architecture. Pretty much the only way to be sure involves taking apart the panel to see the LED arrangement (how many are tied in series/parallel etc.)

[paulstef]

Re: Arquos 70LE640u dead

Very hard to tell. It depends on the architecture. Pretty much the only way to be sure involves taking apart the panel to see the LED arrangement (how many are tied in series/parallel etc.)

I think me taking apart a 70" display is not a good idea, almost certain I'm gonna damage something....

[tom66]

Re: Arquos 70LE640u dead

Agreed, it's extremely difficult to do.

This is the problem with LED TVs - undocumented operating voltages and currents...!

[paulstef]

Re: Arquos 70LE640u dead

The LED strings being sold have 64 LEDs on them , possibly 2x32 in parallel. There are 3 connectors on the wire harness, and there seems to be only one connector on each LED string.

Assuming they use really 3 LED strings, what configuration would that be? Two on top, one in the middle? One on the side? Weird.

[tom66]

Re: Arquos 70LE640u dead

Well each two wire pair will be approx 3.5V x 32 LEDs = 112V DC

You can start with a low current limit, and ramp up. Remember LEDs are current driven devices, not voltage driven. So always use a current limiting power supply, or a current limit resistor in series.

I wouldn't exceed 50mA total.

Not sure on the layout, that is odd. Possibly left & right strips, and one top strip? Weird...

[paulstef]

Re: Arquos 70LE640u dead

Even at 127V there is no current at all through them. Maybe they are all in series...

EDIT:

When forcing the LED driver chips ON the voltage established at the caps ranges from 194 to 184V AND the backlight turns on.

Needed is only :

Shorting PS_ON to BU5v
Shorting STB to BU5V
then
Shorting PWM1 to BU5V.

PWM2 and DIMMER are not used.

Still unclear how to clear the counter in the mainboard without having access to the service menu.....

[tom66]

Re: Arquos 70LE640u dead

OK I don't have any experience with the LED-backlit Sharp sets but I've had the CCFL ones with lamp failures. On those sets holding the buttons on the side of the set (VOL- and INPUT I think) would bring the TV into "K" mode where it can be adjusted. This would turn BL on even if counter has reached max failures. VOL- and CH- would then enter service menu where counter could be reset.

[paulstef]

Re: Arquos 70LE640u dead

Turns out the backlight has the same problem as other Sharp TVs, I've seen a thread somewere here, lower left edge is barely lit...

In adjustment process mode the picture is there ... Awesome :-/

[paulstef]

Re: Arquos 70LE640u dead

Now, did anyone ever succeed in opening such a huge panel and repairing the LED strips?

I think it maybe best to remove all the screws that hold the panel together then holding the parts together with tape, flip the whole thing around so it lies on the front and then I could lift up the inner metal plate that holds the LEDs...

Will need to try it.

[newtothis]

Re: Arquos 70LE640u dead

Now, did anyone ever succeed in opening such a huge panel and repairing the LED strips?

I think it maybe best to remove all the screws that hold the panel together then holding the parts together with tape, flip the whole thing around so it lies on the front and then I could lift up the inner metal plate that holds the LEDs...

Will need to try it.

That is how I would do it... I do that to even 42" sets just to make sure no abnormal pressures are applied to the LCD. Still a 70" is going to be so fragile vs the weight of the LCD itself and I would not like to be attempting it myself! If I do get one I am going to get those glass suction cups and create a stand with them mounted.... Lock them to the screen then remove the rear panel.

[mmartell]

Re: Arquos 70LE640u dead

I think it maybe best to remove all the screws that hold the panel together then holding the parts together with tape, flip the whole thing around so it lies on the front and then I could lift up the inner metal plate that holds the LEDs...

Will need to try it.

I do it this way except I use something smaller than the panel to support it (a large footstool) such that it's easier to work around the edges and when the metal bezel is free you simply lower it to the floor. Then you lift the lightbox off the panel.

[paulstef]

Re: Arquos 70LE640u dead

I managed to open it without breaking the LCD. The backlight is 3 strips with 64 LEDs each all on the lower edge. Apparently it's 2x32 LEDs in parallel on each strip. One LED burnt, half of a strip is dead. Shorted the LED, it works again and voltage is lowered, i.e. current regulation of the driver chip seems to work.

Putting it back together will be more difficult.

[Ltank]

Re: Arquos 70LE640u dead

Sharp used to make repair kits for the 60 to 70" sets. I kept the pdf at shop but i cant get to it untill June 3rd. I will check to see if you found the instructins. it tells you how to take it apart. if you cant find it Iwill post it when i get back to shop. Its better than nothing