sharp lc-m3700 displaying video problem

[gmzombie]

ok i have this lc-m3700 older lcd tv and it just stopped turning on. The unit will show a red light and will turn on for about 30 seconds and then display 3/4 of the screen in a up and down rainbow screen then turn back off and red light blinks.
The pic below shows the screen when the rainbow shows up. it only shows up for a few seconds then fades away to black as tv shuts off after that. Also i thought it could be the tcon board so i replaced that with a good one and no change.

[gmzombie]

Re: sharp lc-m3700 displaying video problem

nobody can help with this monitor?

[Th3_uN1Qu3]

Re: sharp lc-m3700 displaying video problem

Seen it before - check the regulators on the mainboard. Specifically the 3.3v and 1.8v ones.

[gmzombie]

Re: sharp lc-m3700 displaying video problem

replaced the main board and im still getting this problem. any other ideas

[tom66]

Re: sharp lc-m3700 displaying video problem

It's hard to say what the main board is on that TV. I'd say it's the input card - with all the connectors - but what would normally be the Tcon (top of display) looks a lot more complex than it should be.

One check, try disconnecting the LVDS cable from input board to Tcon, if lines stay, probably the Tcon or, less likely, the panel. Try turning the set on and off with the connector disconnected. Again rainbow lines point to bad Tcon or possibly (although unlikely) the panel.

Also is the pattern of lines consistent? Does it change from time to time, or when the set is turned off and on again?

[PlainBill]

Re: sharp lc-m3700 displaying video problem

TCON or panel, I'd tend to say TCON. Note that there is no variation in the intensity of a vertical line throughout it's height. Note that (roughly) the left 1/4 of the panel is blank. These indicate an addressing problem.

PlainBill

[gmzombie]

Re: sharp lc-m3700 displaying video problem

i have replaced the tcon board at the top with a known good one. or at least this is what i was told when i bought it on ebay as the guy said the screen worked but the panel was broke.

the rainbow lines never change sides or anything. just fade away after about 5-10 seconds to a blinking red light.

[PlainBill]

Re: sharp lc-m3700 displaying video problem

i have replaced the tcon board at the top with a known good one. or at least this is what i was told when i bought it on ebay as the guy said the screen worked but the panel was broke.

the rainbow lines never change sides or anything. just fade away after about 5-10 seconds to a blinking red light.

Let's verify a few points.

1. Did changing the main board result in any change in the display?

2. Did changing the tcon make any change in the display?

3. Have you tried hooking up a signal source (game console, DVD player, etc) and stepping through the inputs to see if the sound comes through?

4. Does hitting the Menu button make any difference?

If the sound comes through in #3, and the answers to the other 3 questions are 'No', I would have to say the panel is bad. I cannot conceive of any fault in the boards that have not been changed, or a common failure in two the main boards or two tcons that would cause this display.

PlainBill

[gmzombie]

Re: sharp lc-m3700 displaying video problem

i hooked up my ipod to the only input for audio. This is a monitor only there was only one hookup and the speaker was small but i couldn't get any audio.

Neither boards made a difference in the display.

hitting menu or any button did nothing no menu or anything

The tcon board does have a weird connection between the IO board. and when i take the plugs off of the io board it refuses to start. red light to green light for about 3 seconds the red light blinking.

[PlainBill]

Re: sharp lc-m3700 displaying video problem

That indicates the TV is monitoring the tcon and won't start if the tcon is disconnected. As a matter of curiosity, what happens if you disconnect the tcon from the panel?

PlainBill

[gmzombie]

Re: sharp lc-m3700 displaying video problem

when i disconnect all of the ribbons on the tcon board, there are 6 1 left 1 right and 4 top the screen does almost the same thing except when it is supposed to show the rainbow 3/4 screen the entire screen lights up..but is still black.
Then it waits a few seconds and shuts off to a blinking red light.

[PlainBill]

Re: sharp lc-m3700 displaying video problem

when i disconnect all of the ribbons on the tcon board, there are 6 1 left 1 right and 4 top the screen does almost the same thing except when it is supposed to show the rainbow 3/4 screen the entire screen lights up..but is still black.
Then it waits a few seconds and shuts off to a blinking red light.

I can't think of any other tests to perform. I THINK it's the panel, but wish there was a way to verify that.

PlainBill

[tom66]

Re: sharp lc-m3700 displaying video problem

when i disconnect all of the ribbons on the tcon board, there are 6 1 left 1 right and 4 top the screen does almost the same thing except when it is supposed to show the rainbow 3/4 screen the entire screen lights up..but is still black.
Then it waits a few seconds and shuts off to a blinking red light.

Do you mean the display goes white with no connections to the T-con? That is normal.

[gmzombie]

Re: sharp lc-m3700 displaying video problem

well yea the backlights light up,but it only does it at the same time it would show the rainbow.