Author Topic: JVC LT-40C890 & 40C750 no pic but not leds  (Read 1200 times)

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sinclairtv

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JVC LT-40C890 & 40C750 no pic but not leds
« on: July 08, 2021,06:38:45 »
Had these sets in within a week of each other. LEDs checked ok but it was bad connections on the strips to the bar. Mebbe gonna have to open up sets to check leds before ordering strips. Anyone needing a set of new strips lol.
Add Toshiba 40L2863. All use 3 strips
« Last Edit: August 05, 2021,11:18:53 by sinclairtv »

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JVC LT-40C890 & 40C750 no pic but not leds
« on: July 08, 2021,06:38:45 »

Davy

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #1 on: July 18, 2021,08:24:42 »
Not much help I know..... I had a similar telly JVC LT48C570 it'd switch on and then sometimes the led would blink about once a minute or so giving a click from the speakers, thats all it did. Since I couldn't get the firmware I got a board from Ebay that cleared my problem.

The main board is a T.MS3463S.711 with a LSC480 HN08-8 screen.

I would guess you checked the fuse on the Tcon mine was a badge clone for Curry's and PC world and wasn't listed on JVC site - they didn't want to know. What about the 3.3V supply from the DC-DC converter on the main board?


Dave

sinclairtv

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #2 on: July 19, 2021,14:56:52 »
I fixed them by rewiring the board that the strips go onto. Just thought it was strange that I had 2 with the same fault. I didnt remove the board so may have been one of the strips not making right connection.

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #2 on: July 19, 2021,14:56:52 »

cheeky2

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #3 on: October 06, 2021,05:57:15 »
I have had a similar issue with a Toshiba 40inch LED set. No illumination which I presumed faulty leds, so used my led tester to power them up (without removing taking the screen apart)and they all illuminated with around the correct voltage I would expect for the amount of LED's inside the set. So re plugged the connector back in just to test and all leds illuminated.
 Anyway after using it for a while a few hours it then went off again.
 So dissembled the screen and examined the leds and connections. Found one of the connector strips had around 1.5V drop across it.
 I find it is way easier to see a voltage drop across the connectors than applying a lot of pressure on the connections to get a good resistance reading. The additional pressure applied can decrease the resistance across the connections giving you unreliable readings. So by looking at the voltage across the connectors is a way more reliable means of quickly checking for any high resistance connections. The higher the voltage drop the higher the resistance.
So the resistance of the connector was just enough to trigger the psu to shutting down the output from the leds. Soldered two wires to the bridge the connectors and it has resolved the issue.

sinclairtv

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #4 on: December 31, 2022,08:42:36 »
Toshiba 43U5863 had the same problem. I scraped connections and even soldered over them but no difference so had to rewire. Read about 15 ohms. 3 leds away so had to replace strips as well.

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Re: JVC LT-40C890 & 40C750 no pic but not leds
« Reply #4 on: December 31, 2022,08:42:36 »

 

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