Looking for couple tips please

[ohmmy]

Re: Looking for couple tips please

Great. If the psu has both a ps_on and backlight on pin, do both need to be triggered on with a resistor?

[budm]

Re: Looking for couple tips please

Yes, each resistor for each signal pin, and sometime the Dimming pin also.

[ohmmy]

Re: Looking for couple tips please

Could someone's briefly explain what voltages you normally look for on a t-con and what they do?

[tom66]

Re: Looking for couple tips please

5V/12V/13V input typically
Logic supply voltages: 1.2, 1.5, 1.8, 2.5, 3.3, 5V.
Panel source driver voltage: AVDD (15~16V)
Panel common voltage: VCOM (AVDD/2 or 7~8V)
Panel gate driver voltages: VON/VGH (+20V to +35V) and VOFF/VGL (-5V to -10V)
Gamma voltages are monotonic around VCOM.

[ohmmy]

Re: Looking for couple tips please

Awesome Tom! Why are there negative voltages?

[tom66]

Re: Looking for couple tips please

Ground is relative.

The way I understand an LCD panel is that the negative voltages take the TFT pixel gate way past the bias point, making sure it stays off. The positive voltages turn the transistor (TFT) from off to conductive, the amount of conduction dependent on the voltage between gate and source.

tl;dr: ground is relative.

[ohmmy]

Re: Looking for couple tips please

Cool. I've read conflicting information about when light is passed through that the TFT is off (non conducting) and others have said that when light is passed through its on (conducting).

Which is it?

[budm]

Re: Looking for couple tips please

Some info.

[ohmmy]

Re: Looking for couple tips please

5V/12V/13V input typically
Logic supply voltages: 1.2, 1.5, 1.8, 2.5, 3.3, 5V.
Panel source driver voltage: AVDD (15~16V)
Panel common voltage: VCOM (AVDD/2 or 7~8V)
Panel gate driver voltages: VON/VGH (+20V to +35V) and VOFF/VGL (-5V to -10V)
Gamma voltages are monotonic around VCOM.

Can you explain what all those labels mean in terms of tcon operation goes? Im only really aware of the low negative and positive signal voltages coming from LVDS cable

[tom66]

Re: Looking for couple tips please

VON/VGH is used to make a row on the panel take pixel information, VOFF/VGL is used to deselect it. The panel is updated rapidly and continuously. AVDD goes to the SOURCE drivers and controls the pixel intensity. Gamma voltages make the pixel colours look even and accurate. VCOM is used to avoid panel DC bias, leaving burned images. Poor VCOM causes violent visible strobe effect.

[randtek]

Re: Looking for couple tips please

A quick tip about adjusting Vs and Va (and a good practice for most types of electronic adjustment)

You should always operate the TV for about 20 minutes to allow it to come to full, normal operating temperature before performing the adjustment. This allows for the most accurate adjustment.

[ohmmy]

Re: Looking for couple tips please

Awesome. Thanks for the info.

I'm curious, does running an LCD backlight at full intensity lessen the ccfls lifespan?

[tom66]

Re: Looking for couple tips please

Yes, but it's not worth worrying about. Typically 50,000 hrs can be achieved by most backlights.

[ohmmy]

Re: Looking for couple tips please

Hi guys, curious.. Why do some lcd tvs have master/slave inverters? Does each board drive different ccfls?

[ohmmy]

Re: Looking for couple tips please

Hi guys, curious.. Why do some lcd tvs have master/slave inverters? Does each board drive different ccfls?

Still wondering about this

Also I've been meaning to ask, what are all these solder lines over traces underneath power supplies? Are they a type of shielding? Thanks to anyone in advance!

[budm]

Re: Looking for couple tips please

They are bare copper traces covered with solder so the trace can handle more current.