Sharp Aquos - LC-52LE640U - Power Supply Error

[wcsd106]

Hello,

I am in the process of diagnosing the problems with a Sharp Aquos LC-52LE640U television.

This television has been having intermittent problems since early 2015 with the Lamp Error counter reaching 5 and causing the TV to display the Lamp Error LED Blink Code until the lamp error counter is reset through the service menu.

Last week, the TV again refused to power up. However, the LED code is now 2 long blinks, 2 short which, according to the service manual, represents a power supply error: Power supply error 2 (*2) UR+13V error.

I have located a replacement power supply board, but I am hesitant to replace the power supply unless it could also be tied to the lamp error problem I've been experiencing.

Any ideas?

[ben7]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Have you actually checked the output voltages of the power supply, to see what they are like?

-Ben

[Terryfictv]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

D7805 on the power board is shorted = replace with MUR460.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Thanks for the replies. I haven't actually had a chance to crack open the case on this TV yet. Had a couple of those Hisense (Crap) tv's in on repair. Will be opening the case tomorrow and removing the power board to test.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Power supply has been removed and is ready for bench testing.

I have attached a picture of the PD connector and pinout.

I know that normally you can turn on a power supply by shorting the PS_ON and 5VSB pins. However this particular board does not have a 5VSB. It has a STB, which I assume is standby, but the adjacent pin to the PS_ON is BU5V.

Before I proceed, which pins should I focus on shorting to get this powered up?

Thanks.


Also, my first order of business was to check D7805 as suggested. With one leg of the diode removed from the board, the diode is testing as OK.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Bench tested the power supply board today.

The pinout was in post #5.

I connected Pin 14 (PS_ON) to Pin 15 (BU5V) which was the only pin that had 5v on it as soon as power was applied to the board.

With a switch connecting Pins 14 and 15, I get no output voltage on any pin except for P13 (AC Det) which shows around 3.3v, and pins 14/15 which are both at 5v. (switched on)

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Any ideas of where to check since I am not getting any voltages except for the 3.3v AC Det and the 5v standby voltage?

[budm]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

How about showing good clear pictures of the whole back side of the TV so we can see all the boards, also the pictures of the whole boards?

[Terryfictv]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Check all the fat, hefty diodes D7806B, etc.
budm is right....send pix of whole boards.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Here are the pictures, as requested.

If you need a closer shot of anything, let me know.

Seen is the unit itself, the TCON board, the Main board, and the Power Supply / LCD Controller board.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Have checked all the hefty diodes. All are testing fine with my BK 5460 bench multimeter set to diode test. All are showing a voltage drop of around .4~.5 volts, infinite when polarity reversed.

Checked the two large electrolytic capacitors wired in parallel, they check out fine.

Going to check the other electrolytic capacitors tomorrow, but visually none of them look bad. C7500 & C7510 are in parallel and may have to come out of circuit for testing as my meter isn't getting a reading on either of them. There is a resistor across them that might be limiting my meter's ability to test them.

[CapLeaker]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

can you provide a better picture of the bottom left or the whole thing again of the power supply? I can't read anything, too blurry. The main board pic is blurry too.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

I will take some more photos in the morning and get them posted. I will use my other camera that will let me get closer.... boards may have to be shot in multiple pics to get the best resolution.

[budm]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

What DCV do you get between the two legs of those two main filter caps (47uF 450VDC) when you force on the power suppl? It should be more than 360VDC.
Pictures provided by shopjimmy.
http://www.shopjimmy.com/catalogsear...?q=LC-52LE640U

[CapLeaker]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Forcing on the PSU, while all other boards are disconnected and see what you get is your best option.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Bud,

When I force the power supply on, I am getting 405.99v DC read across the legs of C7800A and C7800B (The large 450v electrolytic filter caps) With the power supply in standby, I get a reading around 168v.

[budm]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

So the PFC Voltage booster circuit is OK. So when you have all the boards connected back together you do not get the PS-ON signal?

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

I will have to hook everything back up and see.. I'll leave my wire soldered to the board at the PS_ON connector so that I can connect my meter to it.

I would assume it tries to power up, since the sharp V on the front of the tv flashes an error code when I hit the power button on the TV.

Will give it a shot here in a few and see what happens.

[wcsd106]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Curious though, If I measure from the negative side of the large filter caps to pin 1 or 2 (PNL12V) of connector PD (The panel voltage connector) I am getting about 13v AC at those pins, however if I connect the negative multimeter probe to one of the pc board grounding points (GP7006) for example that serves as board ground on the secondary side of the display, I only measure 9 volts AC.

I was expecting DC voltage on that side of the board, and would definitely have expected the voltage to remain the same on the negative side of the filter cap and the ground point.

It's almost like something is floating just a bit above ground on that end.

[budm]

Re: Sharp Aquos - LC-52LE640U - Power Supply Error

Are you talking about the negative leg of the main filter cap? You only use that as the GND ref when you make measurement in the primary side, when you check the PNL12V is in the secondary side so you will use the chassis as the GND ref.