jvc JLC42BC3002, has power, no picture

[gostmn26]

I just got this TV and it turns on. There is no back light, sound, or picture. It and seems like it might be in standby. I have searched around can not find a service manual for this.

From what I have tried to discern so far is this had a power/inverter board and a main/TCON board. Don't know if this is right or not, and need to know where to go from here. I have discovered there is no power outputting to the backlight from the powerboard. If I am understanding this right, The two wires on the left of the power board and what feeds power to the inverter.

[budm]

Re: jvc JLC42BC3002, has power, no picture

The two small white connectors to the left of the large two transformer (HV Inverter transformer) are the HIGH Voltage out put (around 2000V) to feed the lamps inside the panel, DO NOT try to measure that high Voltage unless you want to damage your meter.
We need to find out if you do have PFC boosted Voltage of around 400VDC measured between the two legs of the main filter (big brown cap laying on its side) or not.
the white connector to the right of the power supply-inverter board that goes to the main board has labels for each pins, you need to take the pictures of those labels for us and you need to take the DCV readings of each pin, you must provide the Pin number and pin names for each reading of each pin.
I.E.
Pin 1, +5V = XXX V
PiN 12, 12V = XXXX V
we need to know if you have all the correct Voltages and the command signals or not.

[gostmn26]

Re: jvc JLC42BC3002, has power, no picture

On the connector I got this

Pin1, 5.2v = 5.27Pin
Pin 2, 5.2v = 5.27
Pin,3 5.2v = 5.27
Pin 4-7 GND
Pin 8, +12v = 12.13
Pin 9, +12v = 12.13
Pin 10, +12v = 12.13
Pin 11, Remote on/off = 3.22
Pin 12, BL on/off = 0
Pin 13, lamp status = 3.33
Pin 14, dimming signal = 3.26

Measuring the cap with the TV on it measured 390v dc.

I can power the TV on with the panel button but the only way to turn it off is unplug it.

[ZnsaneRyder]

Re: jvc JLC42BC3002, has power, no picture

I repaired a JVC similar to yours. It would not come out of standby, and it was a mainboard.

Vizio/JVC are both made by amtran BTW.

[budm]

Re: jvc JLC42BC3002, has power, no picture

'Pin 12, BL on/off = 0'
The main board is not sending the Backlights ON command to turn on the backlights circuits.
The backlights can be forced on for testing by disconnecting the BL on/off wire going back to the main board first, then use 470~1K resistor between the BL on/off pin of the power supply and the 5.2V pin to force on the backlights, and if other function of the main board is OK, then you should see pictures and get sound, etc, but it sound like you have more than just backlights not coming on if you have to unplug the power cord to turn off the TV.

[aaronwt6]

Re: jvc JLC42BC3002, has power, no picture

I repaired a JVC similar to yours. It would not come out of standby, and it was a mainboard.

Vizio/JVC are both made by amtran BTW.

I 2nd this. Typical failed Amtran main board. Most likely bad eeprom and/or voltage regulators.

[martino]

Re: jvc JLC42BC3002, has power, no picture

I can power the TV on with the panel button but the only way to turn it off is unplug it.

Sounds a awe full lot like bad voltage regulator on main board.

[gostmn26]

Re: jvc JLC42BC3002, has power, no picture

Just to clarify are you saying a 470 ohm 1 watt resistor?

I'm learning electronics as I go here.

[budm]

Re: jvc JLC42BC3002, has power, no picture

Anything between 470~1000 Ohms range resistor will be fine, 1/4 W will be fine.

[gostmn26]

Re: jvc JLC42BC3002, has power, no picture

I just happened to have some 1k 1/2 watt resistors left over from when I made a JTAG to repair wireless routers.

The backlight comes on, however, I still get no response from the controls and no picture or sound coming out. Well the screen is lit up but there is nothing there. Clicking the menu shows nothing.

Is this then as the others have said lean toward the main board, considering the controls are unresponsive. Are there other tests to run to verify?

[budm]

Re: jvc JLC42BC3002, has power, no picture

Main board problem.
You can check the Voltage regulator ICs, heat and cool the board to see if it makes any difference, bad EEPROM, etc.

[ZnsaneRyder]

Re: jvc JLC42BC3002, has power, no picture

I actually put a Vizio board in the JVC TV, but I HAD to use the a Vizio remote, because the JVC remote code is different. The Vizio board was cheaper, that's why I did it that way. Plus, kinda cool seeing the Vizio logo on a JVC TV lol.

[gostmn26]

Re: jvc JLC42BC3002, has power, no picture

I would be up for putting a Vizio mainboard in this TV. I just happen to have 2 Vizio remotes laying around anyway. I just can not figure out what model Vizio TV this would compare with.

[ZnsaneRyder]

Re: jvc JLC42BC3002, has power, no picture

I was slightly off, the one I repaired was a JLC47BC3002. (47 inch) I am looking at the old board now.

My JVC board is #3647-0642-0150(5A) The Vizio version is #3647-0612-0150 from a VIZIO E471VLE

The picture of your board looks exactly like the dead JVC board I still have. The boards that I referenced are for 47 inch, I don't know if the 42 inch is compatible or not, but I doubt there is much difference.