Vizio vo420e no 12v

[shadetreetrader11]

I have a vizio 420e that is missing 12vdc on the power supply. 5v standbye is present. I purchased a eprom from SJ and installed it on the main board already. When you push the "power on" button, the main board does send the 3.3v to the power supply telling it to turn on. The Vizio light on the bottom changes color from yellow to white, but that's as far as it goes. Main caps have 168v.

[budm]

Re: Vizio vo420e no 12v

Please provide us the Voltage readings of all the pins of both connectors:https://www.badcaps.net/forum/attach...6&d=1533524257
Please make sure to put down the pin name and follow by the reading when TV is OFF and when the power switch is activated.
We also need the pictures of the whole backside of the TV showing all the board and straight shot of the whole bottom side of the power supply board.
The more details we have the better. Did someone else work on this TV before?

[CapLeaker]

Re: Vizio vo420e no 12v

If you only get 168V DC at the main filter cap while the PSU is turned on, then the PFC isn't working. No PFC, no 12 and 24Volts.

[shadetreetrader11]

Re: Vizio vo420e no 12v

Sorry BudM Lets try this again

Tv off
168v on main caps

dim-0v
inv on-0
vbr_a-0
blank
status-0
blank-0

on/off-0
12v-0
12v-0
12v-0
gnd
gnd
gnd
gnd
gnd
st/5v- 5.19
st/5v-5.19
st/5v-5.19

TV ON
168v on main caps
dim-0
inv on- 3.28
vbr_a-0
blank
status-0
blank-0

on/off- 3.19
12v-0
12v-0
12v-0
gnd
gnd
gnd
gnd
gnd
st/5v- 5.19
st/5v -5.19
st/5v -5.19

[budm]

Re: Vizio vo420e no 12v

Vizio 0500-0412-0750 (PLHL-T802A, 3PCGM10001A-R) PS
http://www.shopjimmy.com/vizio-0500-...wer-supply.htm

I will have to trace out the circuit on the bottom side of the board to get the test points to test.
In the mean while check the fuse F601 (white rectangular box) right next to the two main filter caps.

[shadetreetrader11]

Re: Vizio vo420e no 12v

Fuse is ok

[budm]

Re: Vizio vo420e no 12v

Fuse is ok

OK check the resistance of PFC diode D606 to see what kind of leakage resistance it has.

[shadetreetrader11]

Re: Vizio vo420e no 12v

.450v and nothing the other direction. I used diode mode and I checked it in circuit .

[budm]

Re: Vizio vo420e no 12v

I am looking for resistance.

[budm]

Re: Vizio vo420e no 12v

What is the O/N of U501?
U501 is for 12V power supply.
Vizio 0500-0412-0750 (PLHL-T802A, 3PCGM10001A-R) PS.
Pictures provided by shopjimmy.
This is going to be tough tracing the circuits, those black paints are covering up the traces.

[shadetreetrader11]

Re: Vizio vo420e no 12v

U501 is a q0465r

[shadetreetrader11]

Re: Vizio vo420e no 12v

I imagine you want me to trace the 3.3v from the "power on" pin back to some form of an oscillator IC?

[budm]

Re: Vizio vo420e no 12v

https://cdn.badcaps-static.com/pdfs/...355a828787.pdf

[budm]

Re: Vizio vo420e no 12v

I imagine you want me to trace the 3.3v from the "power on" pin back to some form of an oscillator IC?

Need to find out which opto isolator is used for turning on the switched VCC to run the PFC and the rest of the power supply.
It looks like PC102 is the one.

[budm]

Re: Vizio vo420e no 12v

Can you read U801 PFC controller IC, we may be able to trace the VCC pin of that IC back to the switched Transistor that supplies the switched VCC.
So far it looks like OPTO PC102 is used for turning on Q101 to supply VCC to run the PFC IC.
You need to check VDC at the Collector and Emitter with ref. the hot side circuit GND which will be the negative leg of the main filter cap in the hot side.
Make sure to at least plug the TV into the GFCI outlet.

[shadetreetrader11]

Re: Vizio vo420e no 12v

Ok,tonight when I get off from work I'll give it a whirl.

[shadetreetrader11]

Re: Vizio vo420e no 12v

Got to looking at Q101 and if you zoom in you can see a burn spot right in the center of it. If you click on the white picture above the image of the green circuit board there are some voltages for you to look at. I didn't know how to resize it. And Opto PC102 looks like it is the one that goes directly to this transistor.

[budm]

Re: Vizio vo420e no 12v

It does look bad, it is a NPN Transistor, the Collector get the DC input Voltage from the AUX winding of the standby power supply, the Emitter pin is the output pin that feed the VCC to the PFC IC.
BTW, when look at the transistor with the two legs pointing down, the left pin is the Base which gets the bias current from the Opto to turn it on when PS-ON is present then the output at the Emitter goes to the PFC IC.
At this point we need to verify that there is no low resistance reading between the hot side GND and the Emitter since the output may be seeing the shorted/very low Ohm so it damage the Transistor.

[R_J]

Re: Vizio vo420e no 12v

I believe Q101 is the VCC switch, It should have voltage (18-20 volts?) on the collector (use hot ground to measure).the base should have a zener diode (likely 15 volt) and the emitter supplies the VCC voltage (15 volts) for the pfc ic U801.
PC102 should be the opto that turns on the Q101. If q101 is burnt, the pfc ic U801 may or may not be shorted

[shadetreetrader11]

Re: Vizio vo420e no 12v

Emitter to hot ground is 30 ohms. I think you guys mean u601 instead of u801. U601 is a FAN7530. And the Emitter goes directly to the VCC or pin 8 of the U601 IC. I also measured all the other pins of U601 to hot ground and they were all above 1k ohm.
I should also note that the readings were done with the transistor removed from the circuit.