Sharp LC-52D85UN that won't power on

[jrudasill]

I have a Sharp LC-52D85UN that won't power on. The Power and OPC lights blink 2 times together and then the OPC light flashes 3 times by itself. I pushed the volume up and channel down buttons while plugging in the power and the backlight came on, but I can't get the TV to display anything with the remote or side buttons. I can power it off and on with the remote and the power button after I get it on as described above. If I hit the Menu button on either the TV or remote, the screen seems to get a bit brighter and the reverse when pressed again. Even though the backlight came on, could this still be a power board issue or possibly the main board? Any assistance would be greatly appreciated.

[Hendog]

Re: Sharp LC-52D85UN that won't power on

Reviving an old thread.

Rather than start a new thread I thought I would revive this one since MY TV model and symptoms are identical. Hopefully I can get a little more traction this time around since more time has passed and others may have since solved this one.

I have a SHARP TV model LV-52D85UN
The TV does not light up. OPC flashes 3 times, power flashes 2 times.

Attached is a screen shot of the Service manual explanation for the symptoms my TV is exhibiting.

I measured the voltages on the power supply board 12 pin connector PD.
Pins 1 through 8 = 0 VDC
Pin 9 = 3.0 VDC
Pin10 = 0 VDC
Pin 11 = 5VDC
Pin 12 = 0VDC

I also have the service manual and the operation manual if required. I'm not sure how to proceed from here and so I'm reaching out for some guidance please?

Thank you,
Henri

[Hendog]

Re: Sharp LC-52D85UN that won't power on

Not "Identical" symptoms...
When I press the volume up and channel down button while plugging it in I do not get any back light however the power LED comes on solid and no other LEDs are active.
So I took another set of voltage readings from 12 power supply board 12 pin PD.
Pins 1 through 4 = 13.14 VDC
Pins 5 through 8 = 0 VDC
Pin 9 = 3.0 VDC
Pin 10 = 2.868 VDC
Pin 11 = 5V (4.98 VDC) I round to 5V on the first set of readings...
Pin 12 = 0 VDC

[Hendog]

Re: Sharp LC-52D85UN that won't power on

TNY264PN voltages with Power Led flashing twice and OPC flashing three:
Pin1=-26.47VDC
Pins 2&3= -29.81
Pin4= -29.45
Pin5=59.3
Pin7=-29.94
Pin8=-29.90

After holding +vol and <chan cycling power I get steady Power LED
Pin1=-26.61VDC
Pins 2&3= -29.65
Pin4= -29.62
Pin5=178.6
Pin7=-30.00
Pin8=-30.00

[dick_barton]

Re: Sharp LC-52D85UN that won't power on

You give the voltage readings but not the pin names. Without a picture of the power supply or the service manual they do not mean an awful lot.

Can you put the names alongside the readings you have given.

[dick_barton]

Re: Sharp LC-52D85UN that won't power on

Pin 12 = 0 VDC
This is the Panel On (PNL_ON) pin and is missing it's input voltage from the mainboard and looks like it's an output from the main BGA chip

Edit
This is from another website "Home Theater Shack"

Hi there, BigBadBill! Is "Aquos" the entire model name/number? I get conflicting info in my searches. Anyway... came across a few posts describing issues with blinking LED's. This one seemed particularly relevant:

'The frequency and color of the blinks will indicate the issue. There is a hold-down button sequence to try to backdoor your way into the set to see if the panel will light. You may have simply racked up too many "weird tuner faults" and need to reset it. My suspicion is that it's either that or bad panel backlight.

Unplug set, press and hold (on set) volume-down and channel-down and hold them while pluging in set. Will come on with "k" on screen, or will crash again if backlight bad. If it stays on, use your remote and arrow right then look for "fact init" and any other reset and turn them on. Arrow back up to "fact init" and hit enter. Let set recycle to green and unplug/re-plug in 5 seconds: the set should be in OOB state'

[Hendog]

Re: Sharp LC-52D85UN that won't power on

Pin 12 = 0 VDC
This is the Panel On (PNL_ON) pin and is missing it's input voltage from the mainboard and looks like it's an output from the main BGA chip

Edit
This is from another website "Home Theater Shack"

Thank you Dick_Barton. You're right I'm missing the PNL_ON voltage. I'll try to include more document details while I'm at it.

I've been focusing on the power supply board given what I've read about them. The problem I have is my PC board component identifiers don't match up with the service manual schematic. On my power supply board RDENCA336WJQZ, I have a TNY264PN commonly found to be bad along with a couple resistors and a diode. So much so, repair kits are easily found on line which contain these components. I don't know if my TNY264PN is bad or not, but the surrounding resistors and the diode are good. I lifted one leg of each and measured them to spec. My schematics don't show these components nor is the naming convention the same. See the attached pic of my power supply board along with the two relevant pdf pages of the power supply board. IC7905 is not in the schematic, yet it's on the board.

Anyhow, if I put that aside and look at that missing PNL_ON voltage, my next question would be: is my CPU faulty? I believe the PNL_ON is an output of the CPU: page 75/106 from teh sharp lc-52d85un manual. If you search the pdf for PNL_ON you will find 5 "hits".

[Hendog]

Re: Sharp LC-52D85UN that won't power on

There is a shortage of parts these days. Even if I wanted to order a main board KE833 XE833WJ, no one has any in stock.

I think I've done what I can with this TV and it might just be time to take it to the recyclers.

[dick_barton]

Re: Sharp LC-52D85UN that won't power on

If your measuring the voltage on TNY264 then the ground connection for you meter would be the negative leg of the 450V capacitor. Your readings in post #4 appear to show negative readings so I assume that you used chassis as the groung connection for you meter.
A photo of your power supply could prove useful if it does not match what is given in the service manual.

What is the voltage between the two legs of the 450V capacitor under the large heatsink. It's normaly around 380V DC.

You appear to have all the voltages ie BU5V, +13V, PS_ON, AC_Det so it looks like your power supply is working. PNL_ON is sent to the power supply via the CPU as you noted again assuming that the mainboard matches that shown in the service manual.
It does initially look lke a BGA failure.

I would wait to see what advice others can offer before giving up.

[R_J]

Re: Sharp LC-52D85UN that won't power on

IC7905 is the STANDBY IC, if anything to do with it was bad you would not have the tv turn on at all. The only thing PNL_POW does is control the regulator ic7121 which supplies PNL12V whos input is from the 13.5 volt supply
Try disconnecting the ribbons between the t-con & panel and see if you get PNL12V

[Hendog]

Re: Sharp LC-52D85UN that won't power on

IC7905 is the STANDBY IC, if anything to do with it was bad you would not have the tv turn on at all. The only thing PNL_POW does is control the regulator ic7121 which supplies PNL12V whos input is from the 13.5 volt supply
Try disconnecting the ribbons between the t-con & panel and see if you get PNL12V

Mmkay...What is th e t-con panel? I don't see any IC7121...

[R_J]

Re: Sharp LC-52D85UN that won't power on

Mmkay...What is th e t-con panel? I don't see any IC7121...

T-Con = Timing control board
Panel = Are you kidding?
IC7121 is located on the power supply board mounted to a heat sink.

[Hendog]

Re: Sharp LC-52D85UN that won't power on

OK sure, I see IC7121 on my board. My schematic doesn't jive with my board. I can't tell what does what.

[Hendog]

Re: Sharp LC-52D85UN that won't power on

If your measuring the voltage on TNY264 then the ground connection for you meter would be the negative leg of the 450V capacitor. Your readings in post #4 appear to show negative readings so I assume that you used chassis as the groung connection for you meter.
A photo of your power supply could prove useful if it does not match what is given in the service manual.

What is the voltage between the two legs of the 450V capacitor under the large heatsink. It's normaly around 380V DC.

.

I have two large 450V caps there. I suspect they're in parallel but I don't know for sure. I'm measuring 380 VDC, and yes I was referencing chassis GND when measuring the TNY264.
See pic of power supply board.

[R_J]

Re: Sharp LC-52D85UN that won't power on

If you are so determined that the power supply is bad, order a replacement.
Then you will convinced that this is NOT where your problem is.
The large caps are in the primary and are NOT checked to chassis ground, you must use HOT ground (primary capacitor negative lead)
If you keep doing what you are doing, you WILL need a new power supply.

[Hendog]

Re: Sharp LC-52D85UN that won't power on

If you are so determined that the power supply is bad, order a replacement.
Then you will convinced that this is NOT where your problem is.
The large caps are in the primary and are NOT checked to chassis ground, you must use HOT ground (primary capacitor negative lead)
If you keep doing what you are doing, you WILL need a new power supply.

I'm not determined the PS is bad. I think my writing and punctuation mislead you. I actually believe the PS is fine. The resistors and diode check good. I am getting 380V across the two leads on one of the large 450V cap (NOT referencing chassis). Admittedly I was using chassis when measuring the TNY264, so that's where I went wrong with my meter.

I'm thinking the CPU is faulty because I'm not getting an output from the PNL_ON line. Thank you for outlining the Hot and Cold side by the way, that is helpful.

[R_J]

Re: Sharp LC-52D85UN that won't power on

If there is a fault with the panel or t-con board, the main board will not keep the Panel power on. it will detect the fault and shut it down. That's why you try and eliminate the panel as the cause by disconnecting it from the T-con board.

[JOHNZHANG]

Re: Sharp LC-52D85UN that won't power on

I had the same problems for this model TV(LC-52D85UN), any solution or advice. THX in advance!!!!