TV starts but no picture, sometimes I get picture and everything

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Television

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Erik @vasso123

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Posted: Aug 25, 2018

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TV starts but no picture, sometimes I get picture and everything

So, I got a ‘‘JVC LT-40E71(A)’’, when turning it on the standby button goes from red to blue like it should, everything is fine there. but the problem is that the logo only pops up sometimes, when it does the TV works fine,.

95% of the time the screen gets back-lit and just stays dark, whats the problem?

I’ve been looking around for a psu but I would like to be sure that would fix it before I buy anything.

Thanks in advance!

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oldturkey03 @oldturkey03 Rep: 782.3k 1.1k 893 2.3k · Answer 1 · 2018-08-25T10:33:18-07:00

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oldturkey03 @oldturkey03

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Posted: Aug 25, 2018

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@vasso123

this could be a bad power board as well as a bad main board. rembmer that it is the main board that sends the signal to the power board. Your JVC is a bit tough to find schematics for, we’ll need to depend on your skills here. Go ahead and post some good pictures of your boards with your question. That way we can see what you see. Use this guide Adding images to an existing question for that.

Your power board TV3902-ZC02-01(C) is also use in also used in Haier 40D3500M Haier le40f3000w. That is just an FYI ;-). Check the voltages on COM4 on the power board. This would be great to measure when it works and when it is not. That would give us a good indication. Anyhow, check these values:

CON4

Pin number Signal name

1 NC

2 GND

3 GND

4 +5V

5 POWER ON/OFF

6 +5VSTB

7 +5V

8 +5V

9 GND

10 GND

11 GND

12 +12V

13 +12V

You can also measure these cicuits and see what values you get.

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21 Comments:

I tagged around 30 pictures total of everything in the tv as I dont want to miss something I dont know about.

the TV is in your capable hands, thanks for the help

Aug 25, 2018 by Erik

I also wanted to mention that; if I wait a couple of days and try to turn the TV on again it usually works for a few ons and offs, but after that it just wont show any picture again.

does that sound like a powerboard thing, mainboard or both?

Aug 25, 2018 by Erik

@vasso123 that could be capacitor as well as MOSFET transitor issue. Let's see what we can find out.

Aug 25, 2018 by oldturkey03

I dont have any equipment to measure such things, but it pretty safe to assume its a powerboard issue right?, or its a fair chance it is.

And I can get a Haier le40f3000w as a replacement board?

Aug 25, 2018 by Erik

@vasso123 it's a bit of a crap shoot between the power board and the main board. I woukld start with the power board but get it from a seller where you can return it, just in case the issue is the main board. Just do a search for a TV3902-ZC02-01(C) power board.

Aug 26, 2018 by oldturkey03

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