32" Dynex DXL3210A Won't Power On

**tieny** · 07-23-2012, 02:10 PM

Re: 32" Dynex DXL3210A Won't Power On

I've been trying but still having a really hard time finding one.

**ben7** · 07-23-2012, 02:13 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tieny

I've been trying but still having a really hard time finding one.

Have you checked to see if it goes down the left side, under the plastic of the connector?

**tieny** · 07-23-2012, 02:30 PM

Re: 32" Dynex DXL3210A Won't Power On

Alright I think we're finally getting somewhere! I finally found where the trace leads. It leads to what I think is an smd transistor. It just might be the bad component, but is there a way of testing it?

Attached Files

**ben7** · 07-23-2012, 02:35 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tieny

Alright I think we're finally getting somewhere! I finally found where the trace leads. It leads to what I think is an smd transistor. It just might be the bad component, but is there a way of testing it?

First we need to draw out the circuit right there to see what we need to check.

Both transistors in question have the marking "1Et", which is a BC847A.

**tieny** · 07-23-2012, 02:41 PM

Re: 32" Dynex DXL3210A Won't Power On

So how do we draw out the circuit?

**ben7** · 07-23-2012, 02:44 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tieny

So how do we draw out the circuit?

We trace the tracks, and draw it out. I use a special circuit-designing program to draw them out on.
You can try using just a simple paint program, since it will take a while to install more programs...

On your picture, the transistor that is circled in red, where do the bottom two pins goto? I think one of them will go to ground. The other I think leads to R684.

**budm** · 07-23-2012, 02:46 PM

Re: 32" Dynex DXL3210A Won't Power On

Whcih pin that the trace (PSON) is connected to on that transistor (left, middle (top tab), right)

**ben7** · 07-23-2012, 02:49 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by budm

Whcih pin that the trace (PSON) is connected to on that transistor (left, middle (top tab), right)

Top tab. (Collector)

its an NPN transistor.

Im thinking that is the pull-down transistor for the P_ON signal.

**tieny** · 07-23-2012, 02:51 PM

Re: 32" Dynex DXL3210A Won't Power On

Heres what i traced using the continutity function.

I forgot one line, but the two SMD capacitors seem to be in parallel.

Attached Files

**ben7** · 07-23-2012, 02:56 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tieny

Heres what i traced using the continutity function.

I forgot one line, but the two SMD capacitors seem to be in parallel.

So, if im right, this yellow trace should goto a power source? (probably 5vsb)

Attached Files

**tieny** · 07-23-2012, 03:02 PM

Re: 32" Dynex DXL3210A Won't Power On

Yep it leads back to the pin labeled 5VT, back on the connectors.

Attached Files

**budm** · 07-23-2012, 03:22 PM

Re: 32" Dynex DXL3210A Won't Power On

Then you should check the voltage between the Emitter (right pin) and Base (left pin) to see if it has about 0.6~07Vdc, if not, that means the processor is not sending the signal to the base to keep this transistor on (this will cause the PSON to stay lo) when the TV is not on.

**tieny** · 07-23-2012, 03:30 PM

Re: 32" Dynex DXL3210A Won't Power On

Component V604, With red probe on the emitter and black probe on the base, I get a reading of 0.035V. So does this means that the transistor is bad and is the cause?

VS02, I did the same measurement and got 0.683V so just comparing the differences.

**ben7** · 07-23-2012, 03:30 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by budm

Then you should check the voltage between the Emitter (right pin) and Base (left pin) to see if it has about 0.6~07Vdc, if not, that means the processor is not sending the signal to the base to keep this transistor on (this will cause the PSON to stay lo) when the TV is not on.

Do you think the other transistor pulls it high then?

Im kinda thinking the other transistor has to do with this one too. Like maybe they are hooked up as a buffer? (Two inverters)

**ben7** · 07-23-2012, 03:47 PM

Re: 32" Dynex DXL3210A Won't Power On

I'm thinking this is where the signal from some control chip comes from!

Attached Files

**tieny** · 07-23-2012, 04:04 PM

Re: 32" Dynex DXL3210A Won't Power On

Heres what i found going through the trace

Attached Files

**ben7** · 07-23-2012, 04:22 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tieny

Heres what i found going through the trace

You've made a mistake, it doesn't go to the resistor, it goes right under the chip in the corner.
EDIT: oh, you switched from one track to the other, and back again, I see now.

Strange that it connects to the crystal, unless it is supposed to be powered on when the tv is turned on.

Measure the voltage from ground to each end of RS34 back near the two transistors.

**tom66** · 07-23-2012, 04:27 PM

Re: 32" Dynex DXL3210A Won't Power On

The soldered joint near the crystal is to reduce EMI by connecting the case of the crystal to ground creating an RF shield around the crystal.

**ben7** · 07-23-2012, 04:30 PM

Re: 32" Dynex DXL3210A Won't Power On

Originally posted by tom66

The soldered joint near the crystal is to reduce EMI by connecting the case of the crystal to ground creating an RF shield around the crystal.

Im not sure about it though. The white overlay makes it hard to see the traces around there.

It is possible that when the TV is turned on, the PS_ON goes high, and it starts up the crystal oscillator.

**tieny** · 07-23-2012, 04:42 PM

Re: 32" Dynex DXL3210A Won't Power On

What is the function of crystals?

32" Dynex DXL3210A Won't Power On

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