Author Topic: TV turns on, lights up but blank screen & no audio  (Read 791 times)

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Offline AndyMacSteve

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TV turns on, lights up but blank screen & no audio
« on: September 22, 2018, 12:03:20 am »
I picked up my old TV from my basement which I havent used for a year, powered it on, the screen lights up but it is blank with no audio or video output.
The model is a Panasonic TC-L47E50 LCD.

I haven't done too much testing or diagnosis, because I think the problem is not the internal power supply but potentially a problem on the T-CON board or the secondary board(s).

One of the caps measured 300V 10 minutes after unplugging and showed no signs of discharging and some diodes seemed to be shorted (diodes normally allow 1 way power flow only, but this ones seems broke)

Could it be a power supply problem, or a much more complicated T-CON board or other board problems?
 

Offline tpowell1830

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Re: TV turns on, lights up but blank screen & no audio
« Reply #1 on: September 22, 2018, 01:00:54 am »
Can you access the menus?
PEACE===>T
 

Offline Seekonk

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Re: TV turns on, lights up but blank screen & no audio
« Reply #2 on: September 22, 2018, 03:17:02 am »
I had that same problem a couple weeks ago. It was called lightning, hit 30 feet  and blew a hole in the ground. My solution was a DTV converter box fed into AUX. I just wish it hadn't taken out the amplified antenna.
 

Online james_s

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Re: TV turns on, lights up but blank screen & no audio
« Reply #3 on: September 27, 2018, 12:55:00 am »
Did it work last time you used it? Do any of the controls do anything? Does it get moist in the basement where it was stored? How are you testing the diodes? Beware that testing parts in-circuit can give misleading results. I would start by checking the outputs of the power supply, often they are printed right on the board.
 

Offline AndyMacSteve

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Re: TV turns on, lights up but blank screen & no audio
« Reply #4 on: September 27, 2018, 01:06:41 pm »
Im just putting the probes across the two diode terminals, and they give the same resistance in both ways.

And no the controls are doing nothing. Not even the menus.

And I also dont remember any lightning or weather causing problems on my TV
 

Online james_s

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Re: TV turns on, lights up but blank screen & no audio
« Reply #5 on: September 27, 2018, 03:46:09 pm »
A resistance check won't tell you anything, in many cases a modern meter will not pass enough voltage to bias the diode. Does your meter have a diode test function? Most do. It's unlikely the diodes are bad though, if they were shorted the tv would probably shut off, blow the fuse or smoke.
 


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