Vizio VF552XVT, audio, but no backlighting

[Vandy30]

Re: Vizio VF552XVT, audio, but no backlighting

Any component tested on board that shows as bad or look bad on the meter should be removed and retest off the board.

for sure, take m out carefully, test m, and put m back in if good, then you can ether confirm their bad or good, and continue troubleshooting.

Well, my first time desoldering a MOSFET/Transistor didn't go so well...I probably damaged the pcb . The laminate underneath the big base tab on the MOSFET bubbled up some and the first one even peeled up some laminate/copper with it when I removed from the board (I didn't even know that was possible!). Too much heat and prying. The second one came off much easier after I saturated with solder, so at least I learned my lesson, just angry with myself and venting a bit.

On with the results...both of the MOSFETS that tested bad in circuit, also tested bad out of circuit. I will try to source some replacements and cross my fingers that the board will live to see another day.

[selldoor]

Re: Vizio VF552XVT, audio, but no backlighting

Let us know how it goes - if you need help or an opinion on repairing the board post pictures of the damage.

[CapLeaker]

Re: Vizio VF552XVT, audio, but no backlighting

not enough heat and prying too much! Once they are hot, you should just be able to pick it up like nothing, just add more solder maybe. You do need a good soldering iron though. A 25W isn't that great.

[Vandy30]

Re: Vizio VF552XVT, audio, but no backlighting

Let us know how it goes - if you need help or an opinion on repairing the board post pictures of the damage.

I really hate to even post these photos...be gentle lol. I did a terrible job and its quite embarrassing, but I would feel more comfortable letting you guys take a look and getting your honest opinion if this pcb damage can be fixed or not. My main concern is the copper pad on the left that the MOSFET sits on, since it is raised up off the board. Can that just be adhered back down? Will soldering the new MOSFET in be ok if left as is? I probed around on the board just doing continuity checks in the area and it tests the same as the pad on the right, but I may be overlooking something obvious. It's just hanging on by a thread and has me concerned.

I think I need a new tip on my iron as I just noticed that the end doesn't come to a point anymore, some of the metal eroded away. This may be why I had issues transferring heat, but regardless I shouldn't have pried so hard. Also, while I'm at it, I believe I will try a flat tip for the large pad area next time to see if that helps.

[nomoresonys]

Re: Vizio VF552XVT, audio, but no backlighting

ok, could not foresee that you would pry on the component, but mistakes are how we learn, there are some good solder/desolder tutorials on youtube. I'm bad at soldering too.

[budm]

Re: Vizio VF552XVT, audio, but no backlighting

When I remove this kind of SMD, I cut the two legs first then I use my 60W Weller with wide tip and add the solder to the tab for removing it off the board.

[Vandy30]

Re: Vizio VF552XVT, audio, but no backlighting

ok, could not foresee that you would pry on the component, but mistakes are how we learn, there are some good solder/desolder tutorials on youtube. I'm bad at soldering too.

In hindsight I should've watched the videos before digging in lol, I just got the cart before the horse. Thanks for the sympathy.

When I remove this kind of SMD, I cut the two legs first then I use my 60W Weller with wide tip and add the solder to the tab for removing it off the board.

budm, that definitely sounds like the best way to tackle these SMDs.

So, I'm still wondering...should I attempt to patch this thing back together? Will it hurt anything if I leave it as is and solder in the new components? Thoughts? Suggestions? I've got the replacement components ordered already and I'm just wondering if I should do some sort of maintenance on the PCB before putting on the new parts. Thanks in advance.

[Vandy30]

Re: Vizio VF552XVT, audio, but no backlighting

IT WORKED!! I just finished soldering the 2 replacement MOSFETS in the LED Driver Board, connected the board back up, and presto. To the best of my knowledge, the 2 shorted MOSFETS on the LED Driver Board were all that was wrong (knock on wood, it's only been running a short time up to now). I'm guessing there is some sort of feedback loop that detected the shorted MOSFETS which then told the PS to cut power to the LED Driver Board as a safety feature maybe? I'm still not positive on that one, but regardless, it is up and running.

I'd like give a big THANK YOU! to everyone that helped me with this project and also thank for your patience and understanding. This is honestly one of the most informative forums around and has a great community. I definitely learned a lot from this. Thanks fellas! Now to find the next project.

[CapLeaker]

Re: Vizio VF552XVT, audio, but no backlighting

I am glad it worked and thanks for the feedback, so others can learn!

[ny_jets_head]

Re: Vizio VF552XVT, audio, but no backlighting

IT WORKED!! I just finished soldering the 2 replacement MOSFETS in the LED Driver Board, connected the board back up, and presto. To the best of my knowledge, the 2 shorted MOSFETS on the LED Driver Board were all that was wrong (knock on wood, it's only been running a short time up to now). I'm guessing there is some sort of feedback loop that detected the shorted MOSFETS which then told the PS to cut power to the LED Driver Board as a safety feature maybe? I'm still not positive on that one, but regardless, it is up and running.

I'd like give a big THANK YOU! to everyone that helped me with this project and also thank for your patience and understanding. This is honestly one of the most informative forums around and has a great community. I definitely learned a lot from this. Thanks fellas! Now to find the next project.

I have the same set and slightly different back-light issue:
The top part of the screen back light is not on as well the bottom is on but flashes when cold and then stops after it warms up.
There is a red led that flashes
The set functions fine otherwise.


On the LED driver board I have the following off the D442 devices

Drain, Gate, Source
Q4 24.1, 1.0, 0

Q5 24.1, 1.0, 0

Q11 24.2, 1.7 ,0

Q12 24.2, 1.7 ,0

Q212 24.2, 1.9 ,0

Q213 24.2, 1.9 ,0

The Q 4,5 gates stand out as a possible issue with the devices or something else.

Thoughts and suggestions?

Thanks

Edit:
More info...
When powered on with the Visio logo all the back lights are working, the screen then goes black
After that the "No signal" screen is where I get the flashing as well as the partial back light at the bottom.
Possibly chasing the down the wrong cause?? maybe t-con?

[ny_jets_head]

Re: Vizio VF552XVT, audio, but no backlighting

Did factory reset and it still fashes.
Any idea where i should start?

[ny_jets_head]

Re: Vizio VF552XVT, audio, but no backlighting

Update:

This one is going to be a problem to troubleshoot.

Now it's only flickering slightly after its been off for a while... otherwise it has been working flawlessly.