Sharp LC-40E77UN turns off bad IC detected

[icekillah]

ok i just got a sharp aqous LC-40E77UN i had a bad psu i saw a IC on the psu that was blown and it looked like someone shorted it out (see pics). i ordered a new psu and the tv turns off after about 10 seconds no (opc light blink code) when i touch the same ic in the new board it is insanely hot. could it be an inverter issue that is causing this chip to burn out? i dont have any schematics but if you've ever seen this before id appreciate the help i have a multimeter

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

i should say the ic that gets hot is a K915 TNY264pn 61877F

[ENERGYSAVINGS]

Re: Sharp LC-40E77UN turns off bad IC detected

Start by pulling all the connectors from the power supply, (except the input of course)
clip wires if you have to.
then install one piece at a time back to the power supply till you find the offending unusual power drain..
I would start with no load however just to insure the board does not overheat on its own.
-Lemur

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

ok its definitely the main board that is causing my ic to get hot (gets hot when the connector to the main board is plugged in. nothing on the main board is plugged in just the board itself) there is also a orange led that lights up when its getting power. Is there anymore trouble shooting i can do on this board?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

here are some pics. it looks like there is a jumper on the board can i cause any more damage to the set by trying different settings

[ENERGYSAVINGS]

Re: Sharp LC-40E77UN turns off bad IC detected

OK, Good start.
There are scant few things on that main board that can cause that kind of heat on the power board without smoking.
So the processor IC with the heat sink is suspect, I would NOT move jumpers around, it is not going to tell you anything.

Did you try the power board by itself to make sure the IC that overheats, (I assume it's a regulator IC)
doesn't get hot by itself? You MAY have already fried that, though they are generally self limiting, so I doubt it. If that does not overheat by itself, Try plugging in the main board without power, and see what component heats up.
With that kind of power being used something is going to overheat.
Just look for a transistor or other semiconductor that is big enough to drain that power without smoking. If the heatsink warms up, you can bet its the processor, and the board is done.
Tell me what you find.
Check the power board on its own first though. sorry to be redundant, redundant.

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

ok i hooked up just the power (ic's temp stayed the same, plugged in the main and started checking the mainboard the heatsink did not increase in temp but it may have not had enough time. however there is a bga that got a little hotter but the board would turn off before it could burn my finger. (i have an IR solder station) could this bga chip be causing the short?

[ENERGYSAVINGS]

Re: Sharp LC-40E77UN turns off bad IC detected

Almost certainly, the BGA if that has the heatsink on it, but make sure you check the other semiconductors as well, if resistors are getting hot, that tells you nothing, as it takes something they are feeding to warm them up. I see alot of diodes and some other IC's that could take the power without smoking. So check those, but the BGA looks like the culprit. If you can identify a power trace(s) to it,, cut those in a way to be repaired later, (scratch away conformal coating to bare the copper) and you could maybe rule out the BGA that way. Or seeing as it sounds like you have the equipment to remove it, you could do that, but that would be my LAST resort.
Good luck

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

Ok well that kind of sucks, what temperature is too hot? I am planning on getting a ir temperature gauge to help with troubleshooting. At what temperature on a voltage regulator or a mosfet is too much?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

bump

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

ok update i ordered a main board that i kinda thought would not be compatible but it was cheap enough. Now the back-light will come on for a second but no splash screen, however the same ic gets just as hot. Im beginning to think that the psu is back feeding the psu. i would like to check the resistors and diodes around that ic. in a laptop if the main gpu fails there will be no splash screen but this tv has a splash screen. i had two power boards one that the previous owner tried to repair(check out the ic) and the one thats in the tv now, ic still gets hot and tv turns off in a coulpe seconds. it seems to be a common problem with these sharp lcds, lets fix this so it can be a sticky!

[budm]

Re: Sharp LC-40E77UN turns off bad IC detected

That IC is for the 5VStandby power supply, so when you have the power supply by itself, do you get 5VSTBY at the connector? and what do you get when the main board is connected to it, will it maintain 5VDC?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

When the psu is isolated I have one pin @ 4.8 and one pin @ 3.0 volts rest of the pins are grounded @ 0.0 v. The 4.8 pin will stay at 4.8 till everything turns off. If everything is hooked up the wsy it should be the symptoms are PSU gets 5 and 3 volt pins, amber light lights up on the main board, a few seconds go by and then the screen turns off. But the sharp logo comes on and there is a snowy picture tried to enter service mode TV still turns off. I checked the voltage on the MOSFET that gets hot, while the PSU is isolated most of the pins were reading around 30v

[budm]

Re: Sharp LC-40E77UN turns off bad IC detected

"I checked the voltage on the MOSFET that gets hot, while the PSU is isolated most of the pins were reading around 30v" OK, you mean the IC TNY264pn? Otherwise which MOSFET is that?
"The 4.8 pin will stay at 4.8 till everything turns off" The 5VSTBY should always be there as long as the TV is plugged into the AC outlet, it does not turn off when TV is turned off, are you sure you check the 5VSB pin?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

Yes I meant the ic that overheats. When power board is disconnected from the main board I get 4.8v and 3.0v. When everything is hooked up normally 4.8 drops to 0.2 when the TV shuts down couple seconds goes by and it jumps back to 4.8v. Couple seconds goes by and back to 0.2v. I tried disconnecting the tcon from the main and the symptoms are the same. Since the sharp menu pops up when the TV is on, I'm thinking the Main board is good. What do you think? Bad ic? Bad diode back feeding This ic?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

The 4.8 and 3.0 are two separate pins on the PSU to main board connector

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

I would like to check continuity. On the diodes around this ic. Any idea on about how many ohms I should be getting?

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

Bump

[icekillah]

Re: Sharp LC-40E77UN turns off bad IC detected

Ok i did a diode check with the board removed from the tv. when the COM is on the cathode side of the diode I get .329, and when the com is on the anode it jumps up to 1.840 its the biggest diode on the board, does this sound normal?

[PotShotScott]

Re: Sharp LC-40E77UN turns off bad IC detected

I realize this thread is old but did you ever get anywhere on this? I just picked up one of these models and mine turns on for about 10 minutes and then stops working altogether. I have a FLIR thermal camera for iPhone and nothing really stands out thermally.