What Voltages on connector of main board for backlight 55" Jvc?

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JVC Television

Repair and disassembly information for JVC televisions.

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Ric @ric81505

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投稿日: 2026年1月28日

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What Voltages on connector of main board for backlight 55" Jvc?

LT-55N780A

Can someone tell me what voltage I can inject with a variable PSU to test the backlights please?

Set powers on but black screen. No backlight no picture.

I have the back cover off it and there are no lights showing thru the small holes that light usually shines thru, as in back light.

I have seen them light up before and work but they might have been damaged when I was playing around with the TV.

No audio.

I don't have aerial connected.

I suspect the power board and that's why I would like to know what voltage I can inject to see if the back light is there.

Thanks for your input.

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Hi @ric81505

Just verifying that with the TV turned on, you can't see any images on the screen (probably very faint if they are there) when using a flashlight held at an angle close to the screen to hopefully see them, is this correct?

If you can't then it could be more than a backlight problem e.g. tcon, mainboard or even screen

Is there audio heard when the TV is on?

What is the model number of the TV?

jayeff さんによる2026年1月29日

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River Park Senior Living @riverparks60351

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5 V standby: ~5.0 V
12 V supply: ~11.8–12.2 V (TV ON)
BL_ON (Backlight enable): ~3–5 V (0 V = OFF)
DIM / PWM: 0–3.3 V (or PWM signal)
GND: 0 V

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Hi @ric81505

Just verifying that with the TV turned on, you can't see any images on the screen (probably very faint if they are there) when using a flashlight held at an angle close to the screen to hopefully see them, is this correct?

If you can't then it could be more than a backlight problem e.g. tcon, mainboard or even screen

Is there audio heard when the TV is on?

What is the model number of the TV? — jayeff

jayeff @jayeff 評価: 532千 11 405 1.5千 · Answer 1 · 2026-01-29T02:06:11-07:00

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jayeff @jayeff

評価: 532千

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405

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投稿日: 2026年1月29日

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@ric81505

Can't find any info on the model but with most TVs the backlights need 80V DC at least.

You said to inject power to connector on mainboard, aren't the backlights being powered from the power board i.e. cable from power board to backlights?

If they are perhaps use a voltmeter to measure between a LED+ lead and an earth (screwhead) on the power board where the backlight cable connects to see what voltage it shows. If it is >100V and there's no backlights chances are they're faulty.

The voltages supplied to the mainboard from the power board are printed on the power board near the cable connector used by the mainboard power board cable.

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Thanks, will try that.

Ric さんによる2026年1月29日

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JVC Television

What Voltages on connector of main board for backlight 55" Jvc?

Update (01/29/26)

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