Discoloured TV when using VGA - Page 1
Forum section: electronics / projects

author: TMFKSOFT
author_rank: Contributor
timestamp: October 29, 2013, 04:54:22 pm
content: I have no clue if this is the right area to post this in!I've had a Flat Screen TV for a while, Its brand is XL.When a PC is Plugged in via VGA or a DVD Player via Scart the display is discoloured as in, its a redish colour.TV Menus are fine.I got it from a family member who had taken it to be repaired and apparently the was an issue with the digital conversion.Sure if a chip had bust it'd not show any video? Is it possible a capacitor has died?I've not bothered opening it up myself just in case it's not worth the hassle, Thought I'd check here.Has anyone encountered this before and does anyone know a possible fix?Thanks,Thomas Edwardsp.s.I'm new to the blog, I've been an avid follower of Daves videos for the past year. Keep up the great work Dave!After watchingfor the 2nd time It gave me the idea of seeing If its possible ot repair my TV! Thankies!

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 29, 2013, 05:08:57 pm
content: Check for a broken pin in the cable or a loose pin in the connector.Do any of the other inputs work fine?

author: TMFKSOFT
author_rank: Contributor
timestamp: October 29, 2013, 05:10:39 pm
content: All pins are fine from just looking at them, Plus Composite seems to be the only input that works 100% fine.

author: DaGlitch
author_rank: Contributor
timestamp: October 29, 2013, 06:25:53 pm
content: Not sure if it's the same for your TV, but when ever I am watching something on the composite and switch over to VGA, my color mode sticks to CMY. I then have to change it to RGB to get things looking right again. Just thought I'd throw that out there.

author: TMFKSOFT
author_rank: Contributor
timestamp: October 29, 2013, 07:41:32 pm
content: There doesn't seem to be a colour mode option, However when changing the brightness I get to about 35% and suddenly it changes to a blue tint instead of red!I'm lost.. I'll have to open it up later and look. I'm not sure If I'll find anything though.

author: Alana
author_rank: Frequent Contributor
timestamp: October 29, 2013, 07:46:03 pm
content: Back when geforce 4 mx was a good VGA card i had my PC connected to TV using composite and had big problems with noise and other distortions due to crap on system ground. Basically TV antenna ground and PC case ground were not the same potential. Maybe you have something alike there?

author: notsob
author_rank: Frequent Contributor
timestamp: October 29, 2013, 07:55:51 pm
content: I see this quite often, throw away your vga cable and get a new one (visually the old one will look ok)

author: TMFKSOFT
author_rank: Contributor
timestamp: October 29, 2013, 10:21:54 pm
content: The VGA Cable is fine, I've tried other Cables etc. Even the usual TV Signal is discoloured.I'm out of ideas. I've been through the menu many times. Im out of ideas other than open it up and have a look around.

author: NiHaoMike
author_rank: Super Contributor
timestamp: October 30, 2013, 01:44:39 am
content: Try doing a factory reset.

author: amyk
author_rank: Super Contributor
timestamp: October 30, 2013, 10:53:48 am
content: Quote from: TMFKSOFT on October 29, 2013, 07:41:32 pmIt seems one of the colour channels is intermittent. Try tracing the signals with a scope from the connector to the image processor, while displaying pure white.

author: Psi
author_rank: Super Contributor
timestamp: October 30, 2013, 12:07:06 pm
content: if a input pin somewhere inside is floating (and it shouldn't be) you might get that.As the brightness part of the circuit changes voltage it maybe causing the floating pin to flip from low to high or vice versa.(The same way floating ADC channels on a MCU will pickup signals on other channels)I would be looking for a cracked or bad solder joint. You may find it comes right when you flex/move the pcb or push down on IC's.Obviously you need to be very careful if you poke around with it running.

author: TMFKSOFT
author_rank: Contributor
timestamp: October 30, 2013, 06:03:39 pm
content: I've tried resetting it, Tried pushing the board in different places etc and nothing seems to affect it.It's still acting like it. I cant find anything visually wrong with the board either.I've ordered a multimeter that im waiting to arrive tomorrow (Sadly its a REALLY cheap one), hopefully I can use that to poke around and see if I can find something thats not right.On a side note. I found some serial pins inside (RX & TX) that would be interesting to poke, Plus the TV has a USB Servicing Port on it which Im interested in poking at..Thanks for all the suggestions.