Help with Sharp TV - LED driver board etc...

[tucocaps]

Re: Help with Sharp TV - LED driver board etc...

Thanks for posting. This thread is of interest to me, as I've recently stripped a bunch of these Sharps, including the model you have. That blink code has always tied back to a faulty panel assembly, and I've not found a way to bypass. Luckily, as AFAIK, the sets all had working boards, but full testing wasn't possible, unless I could retest on a chassis with a compatible panel. The sharp "panel problem" shutdown is really aggravating. Wish there was a way to bypass it.

If I'm not mistaken, on the 70 inch models, you can do a certain keypad press and hold while powering on. I think this yielded a flash of backlight for me in most cases, followed by a steady power light, but still no tv operation.

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

UPDATE:

Since I replaced the power supply board with a refurbished one, the TV does not display any error messages (it used have 2-5 error, pointing to 12V PS problem) . But, even though the LCD does work, and there is a picture and sound, the picture can only be seen with a strong flashlight pointed at the screen. This means that the backlight does not work. I also checked the screen in complete darkness to make sure and there is absolutely nothing coming from the backlight, not even a brief flash or any light leaks anywhere, so I am quite confident that LEDs are not coming on, probably because they are not getting any power.

Earlier I figured that Budm happens to be in my neighborhood, and I got in touch with him. Budm was kind enough to take a look at my old PS board and as he posted here yesterday - it indeed does not produce 12V supply, so that would explain that 2-5 error code.

Now, I also took my original mainboard to him, the one that I have damaged as I was replacing it with a "new" one ("new" being - pulled from a TV with a cracked screen); it had one surface mount cap hanging by a thread... and budm fixed it in no time.

So, now I am thinking of installing that original mainboard back in my TV, while budm is repairing the PS board.

The thinking here is that either the replacement PS board that I have currently in the TV has a problem and therefore there is no power being supplied to the LEDs, or the mainboard that I have in the TV right now is not working properly and perhaps not sending the signal to the PS board to turn on the backlighting. I also have two t-con boards, but they both produce the same result leading me to believe that they are both OK.

I will let you know how things go from here on.

Peter

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

AND FINAL UPDATE:

The TV is working!

OK, so here is the scoop:

Assuming that the problem was maybe the main board, I replaced that first, few weeks ago. That made no difference. Then I replaced the t-con board, and that made no difference. Then, I replaced the PS board (should have done that first, but they are hard to find and these other two I found for a good price) and the TV came ON, but with no back light.

When I was removing the original mainboard, it got a little damaged and then Budm helped me with it and repaired it. I've already put back my original t-con board in the TV and that made no difference, and somehow I thought putting back the original main board would make no difference also.

Well, it did make a difference! I just finished replacing the mainboard - put in the old, original one instead of the "new" one, and the TV came right ON! No blinks, no need to reset anything, it just came ON like nothing was ever wrong. I haven't checked, but it seems that even all my settings are there too (weird?).

Thank you all for your help, especially Budm!

Peter

ps. Now we can debate why the replacement mainboard did not work - could it be different firmware since I could not find anything that looked damaged or wrong with it? It is the exact same model and serial number, with the only difference being the last row of numbers on the ARM chip, which as far as I know usually refers to unimportant stuff such as production series, date and such. Come to think of it, there was someone else on this forum who had very similar TV to mine (also 70" Sharp), and whose mainboard was not sending the signal to the PS board to send the 12V power... hmm...

[petervfx]

Re: Help with Sharp TV - LED driver board etc...

...If I'm not mistaken, on the 70 inch models, you can do a certain keypad press and hold while powering on. I think this yielded a flash of backlight for me in most cases, followed by a steady power light, but still no tv operation.

Yes, usually it is: plug in the power cord while holding the VOL-DOWN and INPUT at the same time. Or in some cases, hold the POWER button while plugging in the power cord. In my case, I could tell that the TV was trying to come on, twice each time, but nothing = and in the end it would just come up with the same blinking pattern 2-5 which is "no 12V supply" code.

Now, it seems that in some other cases, that same code can actually be produced by a faulty mainboard, so that's why I started from there; nothing on my PS board looked bad or burned, and no caps were crowned either. But, in the end, it really was a bad PS board (Budm knows better which component it was that was faulty).

BTW, removing the mainboard is a tricky job as there are SMC on the backside and the metal frame is made of two pieces so as you are unscrewing it, they all start coming apart and can hit the SMC and damage it, so be careful. Theoretically , that should not happen, as there are two screw holes that should keep those two metal frames together, but there were no screws in there - someone at the factory was lazy to put them in - so mine just came apart all at once, while I was taking it apart. I could tell that there were other screws missing also on the PS board... no wonder these TVs have such a bad quality - great design with one of the best pictures on a large screen TV, with incredible color balance and so on, but just awful quality control.

Peter

[budm]

Re: Help with Sharp TV - LED driver board etc...

Glad to hear that the old board is OK.
So I hope the new part will fix the original power supply board then you will have a spare this time. I hope you can get the refund on the replacement main board. I will keep the spare T-CON also.
In the mean time you should reduce the backlights level as low as you can so that it will extend the life of the LEDs.

[budm]

Re: Help with Sharp TV - LED driver board etc...

OK, I received the part yesterday and I just installed it, the board now has 12V_PNL like it should.

[stereojohn]

Re: Help with Sharp TV - LED driver board etc...

Hi i have a sharp Aquos 70" LED LC-70LE632U also and still cant find the faulty part , i got the one fast one slow code so i took appart the lcd from the led panel and it turns on for abbout 2 sec from dim to bright and all the leds look perfect and shuts off i saw once k 70le for a fraction of a second i cheked the power suply board and i cant find a faulty part ???? t-con board disconected makes no difference helpppp

[stereojohn]

Re: Help with Sharp TV - LED driver board etc...

Oh forgot to mention i dont have a service manual ! does someone have one ?

[stereojohn]

Re: Help with Sharp TV - LED driver board etc...

Need help with 70le732

[uigolfguy1]

Re: Help with Sharp TV - LED driver board etc...

@PETER, So I tested out your board, the 12VPNL output is only putting out 7VDC instead of 12VDC. It has bad Q7120: KIA378R12PI so you need to get a new one.
I just placed an order from EBAY.

Hey there Bud, brand new to the badcaps forum. Have the same TV that you all were diagnosing here in this thread. I am a novice at this stuff, but I am learning. I wanted to test this part as you did(KIA378R12PI). I am having a similar issue as Peter, plug the panel in, and get the 2-5 code. I too was reading 7.5V on the PNL12V line when I push the power button. I get my standby voltage, voltage jumps on the AC-DET pin when power is turned on.

My question to you, is how do I test to see if this bad on my board? Do I need to de-solder it from the board? Am I testing in diode mode? If so, what value am I looking for?

I appreciate in advance any help you pass along to me.

[budm]

Re: Help with Sharp TV - LED driver board etc...

You just have to test the Voltage at the input pin of the IC, It should be 12VDC, then output should be 12VDC, but you are getting only 7.5VDC so it is bad.
Look at the spec sheet of the IC to see how it works.

[uigolfguy1]

Re: Help with Sharp TV - LED driver board etc...

Thanks, tested it real quick before work this morning. Getting a standby voltage of 12-13V at first pin, zero on the remaining. When I push the power button, I get 7.50V on the second pin, 0V on the third, and 2.5V on the 4th. I will search for a spec sheet later today, but it sounds like it is bad and I will look online for replacement.

Thanks for you help. I will let you know how it turns out.

[jetadm123]

Re: Help with Sharp TV - LED driver board etc...

All your voltages look good except for the 7.5v output voltage. The 2.5v is the control voltage, which turns the regulator on. The third pin is ground. Regulator is definitely bad. The fun part is removing the heatsink to replace the regulator.

[uigolfguy1]

Re: Help with Sharp TV - LED driver board etc...

Bud/Jet, and to the whole thread, thanks for the advice. Got the parts in today. Heat sink was a little tricky to get, but patience is a virtue. Got the new regulator on there, re-installed the board, and voila...perfectly good TV saved from the scrapyard. Thanks again for the thread and the forum. Huge help! Sorry, the picture is upside down, was best I could do with the TV leaning against my bench.

[budm]

Re: Help with Sharp TV - LED driver board etc...

Thanks for the follow-up on the repair.