Vizio VF552XVT Power Problem.

[budm]

Re: Vizio VF552XVT Power Problem.

You can solder the wires to the caps legs on the bottom side of the board carefully connected them to the meter.
Since the PS-ON is still present when the 12V/18V and 24V supplies go into shutdown like that, it has to be common latched shutdown circuit for both power supplies to go into shutdown like that which is unlikely, something has to be in common to both supplies (12V/18V and the 24V to cause that symptom. I can see just the 24V circuit shutdown but not the 12V/18v too.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

You can solder the wires to the caps legs on the bottom side of the board carefully connected them to the meter.
Since the PS-ON is still present when the 12V/18V and 24V supplies go into shutdown like that, it has to be common latched shutdown circuit for both power supplies to go into shutdown like that which is unlikely, something has to be in common to both supplies (12V/18V and the 24V to cause that symptom. I can see just the 24V circuit shutdown but not the 12V/18v too.

I tested the voltage at the filter cap.

162v off

305v on with CN3 disconnected, (half backlight)

304v on with CN2 disconnected, (full backlight)

305v and a quick drop to 157v when all connected. (supply shutdown)

No leaking when on before shutdown.

[budm]

Re: Vizio VF552XVT Power Problem.

Typical PFC Boosted Voltage is around 380 ~ 400VDC range. That low of the Voltage may be the problem.
Can you read through the heatsink holes to see what Voltage rating of that cap is? It should be rated at 450VDC.
BTW, your power supply board is the same one as shown at shopjimmy?

[wadehavens]

Re: Vizio VF552XVT Power Problem.

Typical PFC Boosted Voltage is around 380 ~ 400VDC range. That low of the Voltage may be the problem.
Can you read through the heatsink holes to see what Voltage rating of that cap is? It should be rated at 450VDC.
BTW, your power supply board is the same one as shown at shopjimmy?

Unfortunately the markings on the cap are on the side that is glued to the board. The bottom of the cap does have a 4XXv on it, but it's cut off to the point that I can't tell what it is.

YES, that is the same board that you linked to on Shop Jimmy.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

Typical PFC Boosted Voltage is around 380 ~ 400VDC range. That low of the Voltage may be the problem.
Can you read through the heatsink holes to see what Voltage rating of that cap is? It should be rated at 450VDC.
BTW, your power supply board is the same one as shown at shopjimmy?

Ok, so I did solder reflowing around the filter cap. The transistors and the ic's on the hot side seemed kinda cold. Now, it turns on and stays on. However, the voltage at the filter fluctuates between 316v and 330v depending on the video that's playing and how bright it is. I'm gonna monitor the voltage for a few hours and see what happens.

[budm]

Re: Vizio VF552XVT Power Problem.

Wells, I think you found the cause of the problem, we just need to get that boosted Voltage up to 380VDC or so, it may have bar resistor network in the feedback circuit in the PFC circuit.
Need to locate the PFC IC and the resistor network on the bottom side of the board.
Do not try to run the TV too long because when supply Voltage is low it will draw more current in the transformer driver circuits so more heat.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

Wells, I think you found the cause of the problem, we just need to get that boosted Voltage up to 380VDC or so, it may have bar resistor network in the feedback circuit in the PFC circuit.
Need to locate the PFC IC and the resistor network on the bottom side of the board.
Do not try to run the TV too long because when supply Voltage is low it will draw more current in the transformer driver circuits so more heat.

I'm not quite sure exactly what I'm looking for. I see a resistor network, and a couple of IC's but not sure which one is the PFC IC.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

I think I found the IC. ICE2PCS02 is it I think.

[budm]

Re: Vizio VF552XVT Power Problem.

https://cdn.badcaps-static.com/pdfs/...f3ef28b014.pdf
As you can see, the Vsense pin is the output Voltage feedback pin so look for a bunch of resistor connected in series between + pin of the filter cap and the primary side circuit GND.

[budm]

Re: Vizio VF552XVT Power Problem.

So PFC IS is IC800 (ICE2PCS02). IC801 is LM293.
Pictures provided by shopjimmy
Vizio 0500-0507-0670 (DPS-450RP A)

[wadehavens]

Re: Vizio VF552XVT Power Problem.

So PFC IS is IC800 (ICE2PCS02). IC801 is LM293.
Pictures provided by shopjimmy
Vizio 0500-0507-0670 (DPS-450RP A)

c819 is the filter cap. There is a small transistor and then a block of resistors that is connected from the positive side of the filter cap and then to pin 6 of IC800 after the resistors.

I'm not sure what to do from here.

Are you saying that the IC is bad? Or that I may have a bad resistor in that block?

[budm]

Re: Vizio VF552XVT Power Problem.

I suspect the resistors have drifted in value, the IC is working otherwise you will not have that 300V, it is just too low than what it should be.
You are going to have to test the value of each one of those resistors.
At this point, the problem is in your power supply board.
I cannot really do much from long distant to be able to trace out the board connections using pictures.
There should be a resistor between pin 6 and GND, if that resistor goes up in value then the output Voltage will be less.
You may want to check the filter cap on the VCC pin of that PFC IC too to make sure it is good, or monitor the VCC pin to see how steady the Voltage is.That darn heatsink is also in the way to see if there are any small lytics caps under that heatsink.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

I suspect the resistors have drifted in value, the IC is working otherwise you will not have that 300V, it is just too low than what it should be.
You are going to have to test the value of each one of those resistors.
At this point, the problem is in your power supply board.
I cannot really do much from long distant to be able to trace out the board connections using pictures.

ok thank you very much for your help. I'll post the findings when I have them.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

I suspect the resistors have drifted in value, the IC is working otherwise you will not have that 300V, it is just too low than what it should be.
You are going to have to test the value of each one of those resistors.
At this point, the problem is in your power supply board.
I cannot really do much from long distant to be able to trace out the board connections using pictures.
There should be a resistor between pin 6 and GND, if that resistor goes up in value then the output Voltage will be less.
You may want to check the filter cap on the VCC pin of that PFC IC too to make sure it is good, or monitor the VCC pin to see how steady the Voltage is.That darn heatsink is also in the way to see if there are any small lytics caps under that heatsink.

I checked all the resistors in the area. If anything they've drifted down a bit, but nothing has gone up in value. The ones closest to the IC are spot on.

Do you think it could just be a bad filter cap at this point?

[budm]

Re: Vizio VF552XVT Power Problem.

If the top strings (the string connected to the cap +) go down in value then the output will be less..

[wadehavens]

Re: Vizio VF552XVT Power Problem.

If the top strings (the string connected to the cap +) go down in value then the output will be less..

Unfortunately they are all fine. It's the string after the transistor connected to the cap + that is lower than they should be. By about 20%.

[budm]

Re: Vizio VF552XVT Power Problem.

20% is a BIG number. Those resistors are at most 5% tolerance for that circuit but more likely to be 1%.
See application circuit here: page 8

Getting 305V instead of 380V that means the output Voltage is only 80% of what the Voltage should be.

[wadehavens]

Re: Vizio VF552XVT Power Problem.

20% is a BIG number. Those resistors are at most 5% tolerance for that circuit.
Getting 305V instead of 380V that means the output Voltage is only 80% of what the Voltage should be.

ok...I'll replace those resistors and see what that does.

[budm]

Re: Vizio VF552XVT Power Problem.

See my update post 37 with application circuit.