Vizio SV420XVT1A LCD 2 Seconds to Black

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Ok that makes sense I thought I was doing something wrong, so I pulled each one and tested all show up 0.L on my meter at all settings for resistance

[cashkennedy]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

>.> budm made the same post about testing the inverters within the exact same time as i was typing my post about it... except his post was better lol

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

OK, the ballast caps seems to be OK (but do not that is 100% true since they may break down when exposed to 2000v), next thing I need to do is to look at the Inverter connections and see how the components are connected together.
Right now I need you to remove that flat aluminum heat sink on the power supply board to see what are underneath. One you have it remove, please make DC voltage reading on the two legs of that large main DC filter cap when TV is OFF (should be around 170Vdc) and when TV is ON (should be around 380~400Vdc). I want to make sure that the PFC is working or not, PLEASE BE REAL CAREFUL, YOU ARE WORKING ON THE HOT SIDE, DO NOT TOUCH THEM WITH YOUR HANDS, AND PLEASE DO NOT SLIP THE PROBES!

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

I will pull the plate off and take pictures tonight. Along with taking those readings.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Ok here are the uploaded pics under the heat sink. The readings are as follows plugged in 164 Vdc and after the power was turned on 391Vdc

Is it normal for those rails to have a charge? I used the positive probe on a screw and then negative on the left rail and with the TV off its 60.3Vdc and with the TV on its 56.4Vdc. Is this normal?

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

So if that dc filter cap is good does that mean it could be between there and the ballast caps I tested or then it could be bad ccfls? Am I jumping to far in assuming?

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

That 391Vdc is good. You cannot use the chassis as part of the Voltage measurement in the Primary side. The Negative leg of the large cap is the circuit ground for the primary side.
Can I get the picture of the whole bottom side of the power supply board? I am having a hard time seeing the MOSFET's and the IC that drive the Inverter transformer.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Here are the photos of the bottomside of the power board. If you need better pics let me know. Photos are uploaded from left to right in order when the board is flipped

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Full bottom image of power board

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

I already have those same 4 pictures you post #14, I will wait for the full view of the bottom side of the power supply bd.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

uploaded image is where the left side is the where the transformers are, thought it would be good to bring them forward in the thread so its easier to reference

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

OK, Please get the P/N of the IC as shown in the PDF. We need to check the VCC pin.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

I think it's pj487 7502 but that is with the naked eye, I will have to get a magnifying glass to verify

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

I Google the numbers but nothing comes up.

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

One thing that I worry about troubleshooting this Inverter section is that there is no easy way to find out if the CCFLs are good or not.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Well if the power board is verified then it leads down the path of ccfls right, isn't it possible to completely disassemble the tv and replace the ccfls? Or am I way off basis.

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

To tear down the panel to get to and inspect the CCFL will not be for the beginner since the LCD panel will have to be lifted off the assembly and put it aside without cracking it, very fragile. We can continue to troubleshoot the inverter section if we can at least get the IC information. We are not 100% sure yet if it is the board or the lamps.

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Once I confirm I will post the p/n of the IC and then go from there

[Crimsonmt]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

Ahh i was so close without a magnify glass, Here is the number off the IC PJ HBY FAN 7602 i beleive there is a B on the third line too, i will be pulling the brown cap and teseting tonight.

So after looking it up it seems I need to check pin6 which is the VCC, Since its on the bottom that means i have to have the board powered on and upsidedown correct? And good tricks to this task?

[budm]

Re: Vizio SV420XVT1A LCD 2 Seconds to Black

You can trace that pin to see where it goes to which I will need that any way, mat be it will be connected to somthing that you can access from the top side.