Vizio XVT3D650SV - Help

[budm]

Re: Vizio XVT3D650SV - Help

Here is the function blocks of the power supply board:
T901 transformer is for:
Rectifier D909 is for 18V (CN203 PIN 3 & 4, filter cap C934), transformer pin 10, 11.
Rectifier D907A, 907B are for 5VSB (CN202 PIN 1~4, CN201 PIN 8~9, filter cap C952), transformer pin 6, 7.
Transformer pin 8, 9 are common ground.

T601 transformer is for:
Rectifier D201 is for 12V (CN202 PIN 10~12, CN201 PIN 6~7, filter cap C203), transformer pin 2, 5.
Rectifiers D120A, 120B are for 24V C121 is one of the filter caps, transformer pin 6, 7.
Transformer pin 9, 10 are common ground.

[budm]

Re: Vizio XVT3D650SV - Help

CN203 pin 3 & 4.Unless the label is wrong, that does not look right, it should be 18V. You do have 5VSB (CN202 PIN 5~8) OK, right?
This 18V is switched through Q912.

[newpey]

Re: Vizio XVT3D650SV - Help

Across the caps

DCV
left: 76.9 right: -55.5
ACV
left: ~63.2 right: ~63.0

[budm]

Re: Vizio XVT3D650SV - Help

Across the caps

DCV
left: 76.9 right: -55.5
ACV
left: ~63.2 right: ~63.0

Are you checking the voltage right at the TWO LEGS (+ and -) of the caps as I requested? You cannot use the chassis for the black probe since you are working in the primary side of the circuit. The measurement are in DC, not AC.

[newpey]

Re: Vizio XVT3D650SV - Help

So the CN203 only has 4 pins:
1&2 SGND i assume that is ground but I cant use that for a ground point to test voltage of 3&4, I have to use the metal of the tv or the ground from another wire. Is that right? Are we looking at the same connector?

[newpey]

Re: Vizio XVT3D650SV - Help

Are you checking the voltage right at the TWO LEGS (+ and -) of the caps as I requested? You cannot use the chassis for the black probe since you are working in the primary side of the circuit. The measurement are in DC, not AC.

Whooops! That;'s what happens when a software engineer uses a multimeter

163.5 volts across the legs of all 3

[budm]

Re: Vizio XVT3D650SV - Help

"1&2 SGND i assume that is ground but I cant use that for a ground point to test voltage of 3&4" YES, you can use that for the secondary circuit ground ref (OR chassis ground) to test the 5V, 12V, 18V, and the 24V.
Right now I need are the voltage on those 3 main filter caps in the primary side to know if the PFC circuit is functioning or not, DO NOT LET THE PROBES SLIP ON YOU while checking. PFC must be working before going any further.

[newpey]

Re: Vizio XVT3D650SV - Help

"1&2 SGND i assume that is ground but I cant use that for a ground point to test voltage of 3&4" YES, you can use that for the secondary circuit ground ref (OR chassis ground) to test the 5V, 12V, 18V, and the 24V.
Right now I need are the voltage on those 3 main filter caps in the primary side to know if the PFC circuit is functioning or not, DO NOT LET THE PROBES SLIP ON YOU while checking. PFC must be working before going any further.

Right on! No zaps tonight! 163 volts on the legs of all 3

[budm]

Re: Vizio XVT3D650SV - Help

OK, that is more likely that the main board is not sending the PS_ON to turn on the PFC, or that the PFC is not working. I am still not sure if you are making the correct reading on the correct pin of the REMOTE_ON/OFF pin.

[newpey]

Re: Vizio XVT3D650SV - Help

OK, so on CN202.. I am testing like this...

Black probe on pin 1 (front right corner - black wire)
pin 2 would be far right back corner.
pin 3 would be front, second to last pin from right
pin 4 behind pin 3

in the picture....
pin 1: black wire
pin 3: red wire
pin 5: yellow wire
pin 7: blue wire
pin 9: grey wire

pin 13 remote on/off would be the 2nd wire in from the left (smaller yellow), up front visible in picture

Am I right or way off?

[budm]

Re: Vizio XVT3D650SV - Help

See the pin 13, as you can see you have ODD and EVEN numbering on the dual-row connector.

[newpey]

Re: Vizio XVT3D650SV - Help

See the pin 13, as you can see you have ODD and EVEN numbering on the dual-row connector.

Awesome .. I get -5.17 with or without pushing power button

[budm]

Re: Vizio XVT3D650SV - Help

OK, so the PS_ON (ON/OFF) control line is stuck on and you do not have PFC voltage function to run the 12V and 24V power supply and turn on the switched 18V power supply. Not good.
Did the problem just happen by itself or the TV was hit by any power surge, etc, or worked on by some one else before?

[newpey]

Re: Vizio XVT3D650SV - Help

That worries me....

So the history of it...

It started to not turn on unless unplugged for hours (overnight) while trouble shooting it, I drained the 3 caps you had me test by shorting them (learned later there are better ways to drain them). This kept the TV turning on while I waited for new caps to come in for the power board as I thought one was swollen. At some point the TV never turned on again. I replaced those caps but still no luck. I figured I fried something somewhere. I ordered a brand new power board and installed it but same issue.

So now I am stuck with it busted and no clue what the issue is other than what you just said (which is more info than i had!)

Soooooo i prob caused it and at least i admitted it but still sucks!

[bammbammfran]

Re: Vizio XVT3D650SV - Help

OK I did some testing on the main board:

Voltage Regulator on bottom right (7806cg rka07):
Pins:
Top 5.17
Middle 5.18
Bottom 5.17
Out 5.18

Voltage Regulator on bottom left: (m462 g1117)
Pins:
Top 5.17
Middle 5.16
Bottom 5.17
Out 5.16
8

These do not look correct considering that the one tab should be a ground.
For instance: on the 7806 ? which I think is a 7805-- it should be the center small pin and the large tab

Are you sure you are using your tester correctly and using a proper ground ?

I have a feeling that the 12 volt supply where I pointed out that F1 fuse that looked questionable should be probably on at the same time as the 5 volts.
Can you post a bottom picture of the power supply board

[budm]

Re: Vizio XVT3D650SV - Help

The 12V and the 24V are generated by the same power transformer T601 and is turned on by the ps_on, the 5vsb and the switched 18V (also turn on by PS_ON) is generated by T901. The 12v/24v SMPS runs on boosted PFC voltage. Also see post 21.
His V readings do look right at all, not sure what he used for GND. REF.

[bammbammfran]

Re: Vizio XVT3D650SV - Help

Thanks bud
Helps to have a good one shot picture to work with
I now see the 5-12-18 & 24 source transformers

Still, those two voltage regulator readings have me confused ?

[budm]

Re: Vizio XVT3D650SV - Help

I am not worried about that right now, it is the PFC circuits that have me concerned since it is not going up like it should, the PS_ON is also at 5V I expect it to be less than 5V due to the bias resistors and the Vbe junction voltage. I have a feeling the ps_on is not getting all the way to turn on the Transistor or the Opto. It is hard to trace out that REMOTE_ON/OFF line to see where it goes. I will have to zoom in more to see. My be you have better eyes than I do.

[budm]

Re: Vizio XVT3D650SV - Help

OK, this is not going to be easy, you will have to get access to Q301 which is the transistor that receives the PS_ON signal fro pin 13, this signal is fed to R310A (1K) to the BASE of Q301. We need to find out what DC voltage we have at E and B, we know that one end of R310A that is connected to pin 13 of CN202 has 5VDC on it, so I expect to see about 0.6~0.8Vdc between E and B. Th hard will be that you will to work with the board powered up which can be dangerous.
Q301 when it is turned on by ps_on, it will then turn on Q302 which will turn on OPTO, then the Photo transistor inside the Opto is turn on which it then turn on the transistor to supply the B+ to run the PFC controller IC and the SMPS IC for the 12V/24V section.

[newpey]

Re: Vizio XVT3D650SV - Help

OK you guys officially have my head spinning. I need to go take some electrical engineering classes to fully understand what is being said above lol!!

Let me test the pins you want. I will also re-test the voltage regulators. I will make sure I use the ground wire/pin