JVC LT-50A330 Backlights turn off after 2-5 min

[SHADOW3277]

Trying to fix this JVC. It will turn on with backlights but after about 2 minutes the backlights cut off. Sometimes they cut off as soon as 30 seconds and I have timed them staying on until 5 minutes but most of the time is about 2 minutes.

With the backlights on I have 3.2 volts at BL_ON and 2.8 at DIM. I also have the same voltages with the backlights off. I have 24 volts coming off the power supply to the LED board. Now here is the interesting thing. I have 3 test points on the LED board that have 13 volts but when the backlights cut off, the voltage jumps to 24 volts. I have attached a picture of the LED driver board with the 3 test points circled. The pin out measurements are below. I am leaning towards the LED Driver board being bad but just want to check that I haven't missed anything. Thanks


CN1 PS to LED driver

Backlights On OFF
Pin 1 VBL 24v 24v
2 VBL 24v 24v
3 VBL 24v 24v
4 VBL 24v 24v
5 VBL 24v 24v
6 GND 0 0
7 GND 0 0
8 GND 0 0
9 GND 0 0
10 GND 0 0
11 ERR 0 0
12 BLON 3.2 3.2
13 NC 0 0
14 E_PWM 2.8 2.8

CN2 LED driver to led's

Backlights On OFF
Pin 1 FB2 0.3v 0v
2 FB1 0.6v 0v
3 PT 2.0v 4.7v
4 CNT 4.8v 4.9v
5 VCC 5v 0v
6 SGND 0 0
7 NC 0 0
8 VBL- 0 0
9 VBL- 0 0
10 NC 0 0
11 VBL+ 0 0
12 VBL+ 0 0
13 NC 0 0
14 E_PWM 2.8 2.8

[CapLeaker]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

Turn down your back lights and see if they stay on longer? If it does, you may have a LED going bad. Or a loose / bad connection cold solder joint somewhere.
Check the DC Voltage of each LED string on and then again when the error occurs.
Somehow the VCC 5V is gone and the FB's are down to zero.

[ducky29]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

Is it a Vestel power supply?

[SHADOW3277]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

Capleaker - So you're thinking it's a bad LED and not the driver board? I can't take the panel off today to get to the LED's so I'll have to check them out this weekend.

ducky29 - No idea.

[budm]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

There is a slide switch on that LED driver board, did you try to see what it does?
CMO 27-D063847 (VBT70118.00) LED Driver
http://www.shopjimmy.com/cmo-27-d063847-led-driver.htm
Pictures provided by shojimmy.
The VBL+/- is high frequency AC output.
To me it looks like there may be another board inside the panel.
BTW, what is the P/N of that U2 on that LED board? OZ??????/

[SHADOW3277]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

budm - my board doesn't have that switch. It's also a different part number but both were used for the same panel. Here is my board

http://www.tristatemodule.com/VIJ370...ij37001.00.htm

Only difference between the 2 I see is that slider switch.

[budm]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

Do you have the LCD panel model number?

[SHADOW3277]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

V500HJ1-L01 Rev.C1

[budm]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

Something is not right, the more I look at that driver board and the spec of the LCD panel. TV cosumes over 200W, that does not sound right for LED LIGHTS TV.
http://www.beyondinfinite.com/innolux/v500hj1-l01/
It show as CCFL. that board is supply AC to inside the panel, I believe there is another board (Balancer) inside the panel.

It does not use LED backlights.

[SHADOW3277]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

That would make sense. The TV is bulky like an LCD but that LED driver board made me think it had LED's. Never seen an LCD with one before. I'll tear it down to the panel this weekend and check out the balancer board.

[budm]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

I do not know why just about every sellers of the called it LED driver board when the output at VL+/- is high (but not in the 1KV) range Voltage AC.

[CapLeaker]

Re: JVC LT-50A330 Backlights turn off after 2-5 min

So I went looking. Indeed that is a LCD TV. I think SJ has an error as it sez it is a LED driver board?