32" Dynex DXL3210A Won't Power On

[budm]

Re: 32" Dynex DXL3210A Won't Power On

OK, just want to see if the T-CON board is loading down the main board.
Well, how much is the new Main board PCB assembly?

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

Disconnecting the Tcon from the main board and turning on the TV? I just disconnected the cable going to the Tcon while everything else is still connected and tried turning on the TV but still no response.

[budm]

Re: 32" Dynex DXL3210A Won't Power On

Well, the processor is bad or it has stuck output, but lets say that it is just this output is bad and other sections of the processor are working, then you should see the pictures and sound when you turn on the TV if all we have is just stuck on PSON, but that is not the case since you are not getting any functions on the TV at all either.
Does not sound good. May be the Xtal for the processor are not working? This is going to be real tough to fix.
Did you try disconnecting the T-CON board yet?

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

I measure 0.683V

[budm]

Re: 32" Dynex DXL3210A Won't Power On

What voltage are you getting at the Base of the first transistor?

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

To find the model, I have to remove the heat sink on the biggest chip correct?

Worst scenario is the main chip is bad and I would have to replace it (I feel like it may be impossible to find a replacement) so I might have to replace the entire board?

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

That is what I thought the output of the processor will be, which is usually active high, so just think of the two transistors as switches. When the output of processor is sitting at '0' (which it should be normally when the TV is OFF) the first transistor is turn off which will cause the second transistor to turn on, so the output (PSON) will be lo, when the processor wakes up and its output goes HI, then the first transistor will turn ON, which will cause the second transistor to turn OFF which causes its out put to be HI (PSON = HI = 12V/24V power supply section turns on. Simple.
Now we just need to find out what is the logic level of the processor out put is when the TV is OFF.

Yes we do.

tieny, what model is the processing chip?

I wonder if the chip is bad, or if there is a voltage regulator feeding it that is bad. (Yes I know you checked them, but sometimes they are in the really small 3-pin devices too)

[budm]

Re: 32" Dynex DXL3210A Won't Power On

That is what I thought the output of the processor will be, which is usually active high, so just think of the two transistors as switches. When the output of processor is sitting at '0' (which it should be normally when the TV is OFF) the first transistor is turn off which will cause the second transistor to turn on, so the output (PSON) will be lo, when the processor wakes up and its output goes HI, then the first transistor will turn ON, which will cause the second transistor to turn OFF which causes its out put to be HI (PSON = HI = 12V/24V power supply section turns on. Simple.
Now we just need to find out what is the logic level of the processor out put is when the TV is OFF.

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

Ow, brain overload! Its been a couple of years since I took my circuits class. I reread it a couple times and understand about only half of it. :p

So from trying to understand whats going on so far the problem would be that the second inverter is recieving a high input from the first inverter which allows the current to constantly flow through, or the second inverter is shorted, allowing current to flow through? Or I don't know what I'm even talking about. ;p

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

Nice, I wish I knew more about circuits though

When the input is high, or '1', a current (limited by RS34) flows through VS02's base to its emitter, then to ground. That causes the transistor to turn on and let current flow through its collector to its emitter, then to ground. However, the current is limited by RS33, and the voltage at VS02's collector is about 0.7v. That 0.7v is considered a low state, or '0'.

When the input is low, no current flows through VS02's base, and so it does not turn on. Because of the resistor - RS33 - going from the 5v bus to VS02's collector; and because VS02 is not conducting, there is no current flowing through RS33. That means there will be 0v across RS33, so VS02's collector will be at the 5v potential, or 'high'. (This is assuming that there is NO current flowing towards R648 - the output of the inverter. If there is current flowing through the inverter's output, then there would be a voltage drop across RS33. How much voltage (V) is dependent on the current (I) and the resistance (R). You can calculate the voltage drop by using ohms law, V=IR)

And so there is another inverter made up out of R648, V604 and R649. The two inverters in series make up a circuit know as a buffer. The wiki page will explain more about why they are used.

Hope I didn't overload your brain! :P

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

Nice, I wish I knew more about circuits though

Are the transistor of the cause of the problem?

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

Ok!

Here is the circuit I drew, and it was exactly as I thought it might be, a buffer circuit xD

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

So the red is connected to the transistor base, and I need to figure out where it leads?

Nope, it just connects to a test point (the round solder bump).

Let me try to draw out the circuit.

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

So the red is connected to the transistor base, and I need to figure out where it leads?

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

Now that I realized it, the via actually goes to a test point on the other side of the board.

The blue is the trace that goes to the processor chip, and the red is the trace/TP in question.

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

Since that transistor is not being bias on (when the TV is off) to keep the Collector voltage at lo, then we need to find out where that base (left pin) is connected to, it either goes to another transistor or go to the processor out put though something like a 1K resistor.

The base connected to the 10k resistor. You are right though, there is a via, i'm not sure where it goes though.

[budm]

Re: 32" Dynex DXL3210A Won't Power On

Since that transistor is not being bias on (when the TV is off) to keep the Collector voltage at lo, then we need to find out where that base (left pin) is connected to, it either goes to another transistor or go to the processor out put though something like a 1K resistor.

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

On the photo, The top of the resistor pin measures 1.99V. and 0.68V on the bottom,

[ben7]

Re: 32" Dynex DXL3210A Won't Power On

What is the function of crystals?

They are used as an accurate, high frequency clock for ICs.

Can you measure the voltage from ground to each end of RS34(back near the two transistors)?

[tieny]

Re: 32" Dynex DXL3210A Won't Power On

What is the function of crystals?