JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

[m21bmr]

I have a JVC JLC47BC3002 47" LCD TV that does not power on, and has no lights illuminated when plugged in. I got the TV in this condition, so I don't have a history of it.

Visually, everything looks good to me on both the Main and Power board. I don't see any burned components, or bulging caps. I measured the voltages at some of the points on the Power board. I got 212.0 VAC on both sides of the main power fuse (the only fuse I found on the PCB).

The only voltage I measured from the PCB to Main board connector was 5.14v at the labeled 5.2V terminals, all others were 0V. Full detail below.

DIM = 0V
Status = 0V
On/Off = 0V
Standby= 0V
12V = 0V
12V = 0V
12V = 0V
Grnd = 0V
Grnd = 0V
Grnd = 0V
Grnd = 0V
5.2V = 5.14V
5.2V = 5.14V
5.2V = 5.14V

Any ideas on what to check next? Thanks for any help.

[CapLeaker]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Looks like the main board isn't returning PSon / BLon. STBY voltage is there on the PSU. Equals main board problem.

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Are there diagnostic recommendations for testing the main board, or is it usually recommended to just replace the entire board?

[dskall]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Do you get any change on the on/off terminal when you push power button? If not I would be checking button connector for voltage and response when pushing buttons.

[Andrew F. Ali]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

There are no lights on when plugged in, so in my view there is no Std-By voltage. If we see 5.14Vdc only then my next check would be to remove the cable from the Pwr Bd to the Main Bd and measure the voltages produced by Pwr Bd. The pin marked standby should read 5Vdc. If 0Vdc on that pin and still only getting 5.14Vdc on the 5.2Vdc pins then I'll suspect a Pwr Bd failure. I would measure the voltage across the Main Filter cap as this will give me more information.

[dskall]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

I missed no standby v. Saw the 5v and assumed standby.

[CapLeaker]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

You can try the PSU by unplugging the main board, leave the back lights connected. Then take two 1k ohm resistors and solder one from STBY voltage to On/Off and the other from STBY voltage to Standby. When you plug that PSU in, it should fully turn on and the back lights should be on too.

As far as the main board goes, there is probably a "Mediatek" main processor. You can try reflowing it, but I'll give that only a small rate of success. Depending on you 'skill level' you may just want to replace the main board.

In your case the Standby pin is PSon, the On/Off pin is BLon.

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Thanks for the input so far.
Here is some more information with the cable to the main board disconnected. I still only see voltage on the bottom 3 pins (all labeled 5.2v). Today I am seeing voltage constantly varying between 5.14v to 5.23v. When I measured yesterday, it was solid at 5.14v.
With the connector unplugged, there is still no voltage on any of the other pins.

I can remove the board and check the voltages across the 3 largest capacitors (in the lower right portion of the board as shown in the first photo) if that would help diagnose things better.

[CapLeaker]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

If the main board doesn't return PSon and BLon, the PSU won't turn fully on. All you see is 5V, that's it until you either fix the main or force it on.

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

You can try the PSU by unplugging the main board, leave the back lights connected. Then take two 1k ohm resistors and solder one from STBY voltage to On/Off and the other from STBY voltage to Standby. When you plug that PSU in, it should fully turn on and the back lights should be on too.

As far as the main board goes, there is probably a "Mediatek" main processor. You can try reflowing it, but I'll give that only a small rate of success. Depending on you 'skill level' you may just want to replace the main board.

In your case the Standby pin is PSon, the On/Off pin is BLon.

I'm pretty inexperienced at this, so just to be sure I'm understanding correctly, it appears that you are calling the three 5.2V terminals "STBY voltage". So I would solder a resistor between one of the three 5.2V terminals and the "Standby" pin to turn on the PSU, and then another resistor to the "On/Off" to check the power to the backlight.
After that is done, if the PSU is working properly, the backlight would be on, and the 12V terminals should show voltage.

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

More results:
I did not have any 1k ohm resistors, but I used two 3k ohm resistors that I had.
I connected the resistors from a 5.2V output to the "On/Off" and "Standby".
The backlight worked, and here are the voltages measured from the 14 pin connector output:
DIM = 3.33V
Status = 0V
On/Off = 4.64V
Standby= 5.21V
12V = 11.84V
12V = 11.84V
12V = 11.84V
Grnd = 0V
Grnd = 0V
Grnd = 0V
Grnd = 0V
5.2V = 5.30V
5.2V = 5.30V
5.2V = 5.30V

So from these results, am I correct in assuming the PSU is functioning properly and the main board is the problem, as CapLeaker suggested earlier in this thread?

[CapLeaker]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Very good! You are on the right path!

[dskall]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

I'm confused when does standby = pson? Not doubting just slow learning curve

[CapLeaker]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Learning curve, yes... I fell for the same thing many moons ago. Trust me, there are a bunch of folks that get confused with that.
If you follow the pins on the PSU on picture #2. You need to have PSon and BLon. It can't be the Status or the DIM pin, so there are only 2 pins left. The Standby and the On/Off pin. There is no standard set by the manufacturers, just a bunch like to call them PSon and BLon because it is short and it does identify perfectly what is what.
Also you could trace it out on the back side of the PSU.

[dskall]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Learning curve, yes... I fell for the same thing many moons ago. Trust me, there are a bunch of folks that get confused with that.
If you follow the pins on the main board on picture #2. You need to have PSon and BLon. It can't be the Status or the DIM pin, so there are only 2 pins left. The Standby and the On/Off pin. There is no standard set by the manufacturers, just a bunch like to call them PSon and BLon because it is short and it does identify perfectly what is what.
Also you could trace it out on the back side of the PSU.

Well first for me. Only seen standby as well standby. Thanks for info.

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

I purchased a used Main board for the TV (that stated it had been tested) and now I have:
Red light on front of TV on when plugged in. Pressing power results in the white light on the front of the set turning on, but the backlight does not turn on. Once the white light is on, pressing the power doesn't do anything. I must unplug the TV from the wall to get the white light off.

Here are the voltages measured at the 14 pin connector when the white light is on:
(all voltages were 0 with the bottom 3 measuring 5.14V with TV off and only red light displaying on the bottom of the set.)

DIM = 3.31V
Status = 0.02V
On/Off = 0V
Standby= 3.26V
12V = 12.3V
12V = 12.3V
12V = 12.3V
Grnd = 0V
Grnd = 0V
Grnd = 0V
Grnd = 0V
5.2V = 5.14V
5.2V = 5.14V
5.2V = 5.14V

Any ideas about what the next step is?

[budm]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

"On/Off = 0V' The main board is not sending the BL-ON signal to turn on the backlights circuit.
And also other problem as well on the main board based on this statement: 'I must unplug the TV from the wall to get the white light off.'

[m21bmr]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

I thought I would post what I ended up doing on the TV. As I originally saw on another thread here on Badcaps, the JVC JLC47BC3002 and the Vizio E471VLE are almost identical TVs (both manufactured by Amtran). The lcd panels and power supplies are common, as is the form of the main board.
I ended up returning the non-functional replacement JVC main board that I bought, and getting a Vizio E471VLE main board. When I installed the Vizio board, everything works properly. The only consequence from the Vizio board was having to switch to a Vizio remote control.

[vinceroger69]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

Thanks for the update glad the replacement board fixed the issue

[mattress]

Re: JVC JLC47BC3002 47" LCD TV Dead - No power on , no lights

I'm having the exact same issue here. I'd like to avoid replacing the main board if possible ($100).... but I don't know how to diagnose bad hardware without visual indicators. I attempted to "reflow" the CPU with a heat gun but did not change anything. I don't see any bulging or leaking caps, no burn marks, fuses are good. Looks like I'm getting correct voltages from psu. I was able to jump 5v to "on/off" and "standby", and got the backlights to come on. I also understand a bad eeprom/ bad CPU is also likely with these cheap sets... and I guess that wouldn't be testable ... I saw this thread where another Amtram tv was brought back from the dead with a firmware update. I can't seem to find one for this tv...