Videokarma.org

Go Back   Videokarma.org TV - Video - Vintage Television & Radio Forums > Flat Panels & Digital Format

We appreciate your help

in keeping this site going.
Reply
 
Thread Tools Display Modes
  #1  
Old 08-23-2018, 12:47 AM
cademan cademan is offline
VideoKarma Member
 
Join Date: Dec 2007
Posts: 23
Toshiba flat screen tv

Hi all, I usually hang out at AudioKarma. I know electronics and I am mostly into tube equipment and the audio side of things. Anyway, I have a Toshiba flat screen which seems to have an intermittent problem.

I thought I would run it by a few people here who are more knowledgeable with the flat screen technology.

The tv was given to me for free, and it was said that it didn't work but when I got it home and plugged it in, it worked fine..........for about a month but then it went out and now it won't work again. It seems like the back lit panel isn't working right as when you first turn it on, it will flash a picture on the screen but then go dark. The front panel power indicator light used to glow solid green but now only glows for a second and then goes dim.

Would this be a bad capacitor? Bad back light transformer? Power supply? I can easily check these things but just wanted some general input here before I open it up and dive in. My forte' is audio so I am not much of a tv guy or couch potato.

This thing only has one single circuit board with all the parts, and a few wires running to the back light panels. That's it.

Any general ideas?

Appreciate any replies. Thank you!
Reply With Quote
  #2  
Old 08-23-2018, 10:16 AM
Electronic M's Avatar
Electronic M Electronic M is offline
M is for Memory
 
Join Date: Jan 2011
Location: Pewaukee/Delafield Wi
Posts: 14,758
I've only done a couple flat panel displays, but the ones suffering from bad caps would do similar.
If any cans look bulged or like they let gunk out those are definitely bad...Sometimes you need an ESR tester to check. The little $15 Chinese ESR testers on ebay can do this.
__________________
Tom C.

Zenith: The quality stays in EVEN after the name falls off!
What I want. --> http://www.videokarma.org/showpost.p...62&postcount=4
Reply With Quote
  #3  
Old 08-23-2018, 07:07 PM
cademan cademan is offline
VideoKarma Member
 
Join Date: Dec 2007
Posts: 23
Great place to start. Thanks!
Reply With Quote
  #4  
Old 08-25-2018, 11:48 AM
MadMan's Avatar
MadMan MadMan is offline
The Resident Brony
 
Join Date: Oct 2016
Location: Chicago
Posts: 1,217
I would bet on a backlight problem. They're tiny little fluorescent tubes, and like regular fluorescent lights, they get old and stop working. What I've seen happen (in my admittedly limited experience) is that the tubes go bad or weak, and the power supply (think ballast) still sending the tubes high voltage, through tiny wires, and the HV leaks out and arcs to ground. The backlight goes out, obviously, and depending, the power supply may stay on and run the tv anyway, or turn itself off as a sort of failsafe mode.
Reply With Quote
  #5  
Old 09-02-2018, 05:07 PM
cademan cademan is offline
VideoKarma Member
 
Join Date: Dec 2007
Posts: 23
Hmm, I have some capacitors on order but how would I check the back light?

The people that gave it to me said it quit working but when I actually got it home and checked it out, it worked perfectly for about a month. Not a single glitch or hiccup. Nice and bright with no flicker or dimming.

Turned it off one night and then back on the next day and it started doing again what I presume it was doing before I got ahold of it so possibly an intermittent (hopefully easy) problem.

It has a very simple single power supply board with only two outputs. One for the back light and one for the video board. All diodes, bridge and voltage regulator test good.

Oh well, the capacitors only cost me $10.00.
Reply With Quote
Audiokarma
  #6  
Old 09-26-2018, 08:11 PM
mbates14 mbates14 is offline
VideoKarma Member
 
Join Date: Apr 2004
Posts: 1,003
if the backlight pulses and shuts down, you should check the inverter board. They have multiple safetys built in, and if it senses that 1 or more tubes dont fire, it will shut down.

Same thing if the board itself cant supply the correct tube current for one reason or another.
Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:20 AM.



Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
©Copyright 2012 VideoKarma.org, All rights reserved.