How the boards communicate?

[Ashroyer05]

I am a recent grad in electronics so I have a lot of theory and some hands on. Since I have started fixing tv`s (and in some cases attempting) I am curious in how the circuits communicate and in what sequence. The power supply is in standby when plugged in then the main board tells the psu to activate a higher voltage? Is that correct and what happens after?

[Ashroyer05]

Re: How the boards communicate?

More precisely I'm curious in the signals between the boards. If a psu goes high voltage is the signal from the main a constant high for that duration or does the signal go low and then high again when the main wants the psu to reduce voltage back to standby voltage?

[budm]

Re: How the boards communicate?

The signals from the main board to the power supply board and to the inverter boards are usually active HI, it is steady state, usually the HI can be from 2~5V, <1 = LO. Some manufacturers may use active LO. Read the basic troubleshooting guide below.

[cheapie]

Re: How the boards communicate?

In computers, the power supply starts out only supplying only the 5 volt standby (purple wire). When the power button is pressed, the motherboard connects PS_ON (green wire) to ground. This causes 12V (yellow), 5V (red), 3.3V (orange), -12V (blue), and "Power Good" (gray) to come on. When the computer wants to shut down, PS_ON is disconnected from ground, which causes the power supply to switch back to only supplying the 5 volt standby. TVs work in a similar manner.

[Ashroyer05]

Re: How the boards communicate?

Thanks guys. I'm learning more already.

[Ashroyer05]

Re: How the boards communicate?

Does the psu supply a voltage to the mother boards to turn it on and then the motherboard returns a separate voltage back to the psu to have it go to full voltage? I'm confused because a tv i'm working on now it has 3.2 all the time in one pin. When I turn the tv on another pin goes to 5.18 until the screen shuts off then back to 0 but the other pin with 3.2 stays the same. OR does the motherboard operate off of standby voltage. the thing is though that the 5 v pin goes high even with the mother board disconnected, so I know the mother board is not the one sending the 5v back. So basically my psu wants to send 3.2v and 5.18v to the mother board.

[budm]

Re: How the boards communicate?

The mother board or the main board will be running of the 'ALWAYS ON' standby power supply (it can be 3.3V STBY or 5VSTBY. The stby power supply will run the minute you plug the power cord into the AC outlet, this STBY is used to run the uController or CPU (not all the function of the u or CPU will be running) which is awake just enough to get the ON signal from the soft switch or from the remote, once it receives the signal, the main board will send the signal to turn on the rest of the power supply.

[Ashroyer05]

Re: How the boards communicate?

So the main board will send a separate singal back to the psu to go full power? Will this be on a separate pin? How much voltage does it send the 2-5?

[budm]

Re: How the boards communicate?

For TV, the signal is usually labeled with PS_ON, or STBY, or PWR_ON. < 1VDC is OFF 2~5VDC is ON. Read basic guide below.
https://www.badcaps.net/forum/showthread.php?t=25810

You can also read the training manual.