Vizio E550VL Black Screen/PSU

[msrods]

I have replaced the T-Con and mainboard and nothing but when I look at the PSU resistors R304,305 and 308 only read 28 Ohm. They are marked 68 Ohm. Back of the PSU at resistors location is yellow compared to the rest of board. Is it possible why all I am getting at the 24VDC pins for the master and slave only 8 VDC. I am a novice so any help would be greatly appreciated.

[budm]

Re: Vizio E550VL Black Screen/PSU

Start by uploading good clear and well focused pictures of the whole back side of the TV so we can see how all the boards are connected together, then pictures of the TOP and BOTTOM sides of the power supply board.

[Alastair E]

Re: Vizio E550VL Black Screen/PSU

Does voltage rise when BL boards disconnected...?

[msrods]

Re: Vizio E550VL Black Screen/PSU

No it does not. It falls off slowly to 4 VDC and holds there. BTW If someone can tell me how to post the pictures I will.

[msrods]

Re: Vizio E550VL Black Screen/PSU

Start by uploading good clear and well focused pictures of the whole back side of the TV so we can see how all the boards are connected together, then pictures of the TOP and BOTTOM sides of the power supply board.

As per request here are the pictures.

[budm]

Re: Vizio E550VL Black Screen/PSU

"I look at the PSU resistors R304,305 and 308 only read 28 Ohm." They are connected in parallel so the total resistance is about 23 Ohms.
So BOTH inverter boards are disconnected you still do not get 24VDC, right?
Please check the DCV between the two legs of main filter cap C801A when TV is on to see if the Voltage is >360VDC.
Pictures provided by SJ.

[msrods]

Re: Vizio E550VL Black Screen/PSU

Voltage is 168 DVC

[budm]

Re: Vizio E550VL Black Screen/PSU

Voltage is 168 DVC

It should be more than 360Vdc when power switch isactivated and PS-ON is present, so that section needs to fixed or find out what is causing not to work.
So just to be sure, the Voltage on the cap DID NOT JUMP up to >360VDC and then drops down, right?

[msrods]

Re: Vizio E550VL Black Screen/PSU

It goes to 397 then drops back to 169.

[budm]

Re: Vizio E550VL Black Screen/PSU

OK, so the PFC Voltage did come on and then drops out, then you need to find out if the PS-ON signal also drops out or not next.

[msrods]

Re: Vizio E550VL Black Screen/PSU

How do I check that?

[budm]

Re: Vizio E550VL Black Screen/PSU

The white connector on the power supply board that goes to the main board has the pin labeled with name of the pin next to it, so list each pin name and the measured DC Voltage reading (when TV power switch is activated) next to each one.
See CN201:
http://assets.shopjimmy.com/media/ca...0790-top_1.jpg

[msrods]

Re: Vizio E550VL Black Screen/PSU

PS is 2.88 The next 3 which should be 12VDC are 13VDC and the bottom 3 which should be 5VDC are 5.04VDC

[budm]

Re: Vizio E550VL Black Screen/PSU

OK, something does not make sense here, you are saying that you do have 12VDC (13VDC) on the coNnector CN201, but you are getting only 8V on the 24VDC on CN202, CN203. The problem is that the 12V and the 24V are generated by the same circuit, so to have only 8V on the 24V but the 12V is OK does not make sense, I would expect the 12V will be very low also. If both inverter boards are not connected, the Voltage should be a lot higher than 8V.
Something else is also causing the PFC Voltage circuit to drop out also.
You are having the same problem as this one:
https://www.badcaps.net/forum/showth...-321%2A&page=2
But the OP never comes back to tell us what happen after I wasted so much times tracing out the connections.

[msrods]

Re: Vizio E550VL Black Screen/PSU

First off I will stay with this until the problem is solved. I will pull the board and turn it over and check the voltages as indicated on the traced picture. I have been checking all the voltages one the front side at the pins. Maybe I am missing something. Have a Happy Easter.

[msrods]

Re: Vizio E550VL Black Screen/PSU

Don't know if this maters or not, but depending on where I put the ground clip the voltages vary by 4VDC and if I use the sig gnd for the grounds I get no voltage same with the GP1 on the board.

[budm]

Re: Vizio E550VL Black Screen/PSU

Right now we are interested in the 24V power supply section without having the inverter boards connected to CN203, CN202. You just put the meter probe on CN203 PIN 1 (24vdc) and black probe on pin 7 to see what DCV you get.
The boards will be mounted in place.
And in what section are you checking the Voltage, the primary side circuit? the secondary side circuit?
We also still need to find out why the PFC Voltage drops down.

[msrods]

Re: Vizio E550VL Black Screen/PSU

Using pin 1 and pin 7 (black probe) I get no voltage at all. Testing on the secondary voltage side. If I use H55 on secondary side for ground point I get 0 VDC, if I use H53 on primary side for ground I get 20.11VDC.

[msrods]

Re: Vizio E550VL Black Screen/PSU

My post should have said HS3 and HS5 instead of H53 and H55

[budm]

Re: Vizio E550VL Black Screen/PSU

Using pin 1 and pin 7 (black probe) I get no voltage at all. Testing on the secondary voltage side. If I use H55 on secondary side for ground point I get 0 VDC, if I use H53 on primary side for ground I get 20.11VDC.

Primary circuit Ground point cannot be used for the Gnd ref for the seocndary side, and secondary side GND ref cannot be used for the primary Gnd ref.
So pin 1 and pin 7 of the 24VDC output connector is showing 0V but you do have 12V and the 18V?