Vizio VO47LFHDTV10A - No Backlight

[vinceroger69]

Re: Vizio VO47LFHDTV10A - No Backlight

i would wait and see if budm has any ideas on what maybe causing your issues some times you can see a failed ccfl tube but that means stripping the lcd panel down and high risk of cracking/damaging it, so thats your last resort, are the new parts you have fitted to the boards still testing ok? also if you have two inverter boards if they have identical transformers you could measure both for primary and secondary winding resistance and see if they both match.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

are the new parts you have fitted to the boards still testing ok?

Would the fact that I see an image, albeit for a couple of seconds, confirm that those parts are OK?

EDIT: On second thought, maybe that a false conclusion...?

also if you have two inverter boards if they have identical transformers you could measure both for primary and secondary winding resistance and see if they both match.

A good idea, I'll check the winding resistance of the Master and Slave inverter boards... Thanks!

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

A good idea, I'll check the winding resistance of the Master and Slave inverter boards... Thanks!

Checked the resistance of the windings for all four transformers (two per inverter board)... They're all the same.

I turned the TV on several times and noticed that on two occasions, it appeared that one of the ccfl tubes in the center of the screen was off, but I couldn't replicate it after those two times... Maybe a ccfl tube on the verge of failing?

[budm]

Re: Vizio VO47LFHDTV10A - No Backlight

So at this point none of the IC or the MOSFETs are blown, right? Just 3-second to black problem, correct?
It will only take one bad lamp or bad lamp socket (if it uses socket) to trigger protection circuit.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

So at this point none of the IC or the MOSFETs are blown, right? Just 3-second to black problem, correct?

Correct.

Could/would the failure of one or both inverters cause this new failure to occur?

It will only take one bad lamp or bad lamp socket (if it uses socket) to trigger protection circuit.

How does the protection circuit work? Does it sense overly high current?

If it is a bad ccfl or socket, that means I'll have to open up the TV even more to get to those parts... A bad socket would be repairable... A bad ccfl? Probably not.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

It's been over a year, but I finally got back to this HDTV.

Since my last post I haven't turned on the TV... Until now.

It powers up and I have a picture at the moment, but I suspect over time it'll shut itself down like before, like something heats up or charges up. Then it turns into a 2 seconds to black issue.

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

If the transformers test ok, then most likely a bad lamp or lamp socket/connection as mentioned. As always be very careful working in that area DEADLY VOLTAGES, warning is for those reading that may not be aware, safety first.

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

If the transformers test ok, then most likely a bad lamp or lamp socket/connection as mentioned. As always be very careful working in that area DEADLY VOLTAGES, warning is for those reading that may not be aware, safety first.

Thanks for the reminder.

I suppose if I have to get at the lamps/sockets, most/all of the boards will have to be removed and that should eliminate the high voltage threat, right?

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

You probably already did but you could check your 24 volt inverter pins to see if you have steady 24 volts going from powerboard to inverter board/s.

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

When it's in the fault condition could try heating the powerboard and inverter boards with a hairdryer heating the capacitors etc, see if it starts working or anything changes.

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

Thanks for the reminder.

I suppose if I have to get at the lamps/sockets, most/all of the boards will have to be removed and that should eliminate the high voltage threat, right?

Yes, just be careful handling the power board, the big filter caps can hold a big charge for quite a while after power is removed.

[nomoresonys]

Re: Vizio VO47LFHDTV10A - No Backlight

Here's Norcal doing some testing on the same model as yours looks like: https://www.youtube.com/watch?v=jR2UZhoDC2c

[bmwracer]

Re: Vizio VO47LFHDTV10A - No Backlight

When it's in the fault condition could try heating the powerboard and inverter boards with a hairdryer heating the capacitors etc, see if it starts working or anything changes.

So far, the TV's been running fine... I've got a heat gun I can use to warm things up.