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Old 10-10-2021, 08:07 AM   #13
angelos
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Join Date: Dec 2012
City & State: Free State
My Country: South Africa
Line Voltage: 220V AC
I'm a: Professional Tech
Posts: 343
Default Re: JVC TV Model LT-65N675- No picture

Hi Guys, i did further tracing around the voltages that are missing on the TCON and i noted the following. When mains power is applied to the tv the TCONs ribbon supply voltage from the main board is a steady 12V if the set is on standby or ON. This tells me that something else must switch on the 12V when picture is required. I have made some marking on the photo i sent you to explain properly.
ICA1 i assume is either a mosfet or a dc to dc converter, i dont know. What i do know is that when i removed the ICA1 i saw that 4 circuit tracks are common as the 12V input and one is on the output called HVIN_12V. The last pin is a bias pin or enable pin and is driven directly from the RT6931GQW IC.
I was monitoring the HVIN_12V pin when applyuing main power and it shot up to about 3.3V and dropped to zero. It never came up again.
If i measure ohms from HVIN_12V to ground i get 38.5 k ohms so there is no short there.
So here is my conclusion either RT6931GQW is faulty or goes into protection or who knows maybe there is no data from the main being detected by this chip so it does not start up???
The TV lies open awaiting your help.
Thanks so far.
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