Vizio VW42LFHDTV10...Brother Mikes TV...

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...what parts

I'm trying to boil down the trouble with this set and get on to deciding what may need replacing of parts. From all the threads I've read here about similar sets with no picture and no back lights, the fix has usually been the replacement of the slave inverter board. An occasional bad cap maybe, but like mine, the power supply board checks out, as do the ccfl's; also no one has done much on main board except the readings I have reported in this thread.
These are the parts that have been implicated on the inverters: the four 8847L transistors on each board, the video driver chip BD99897F on the master board, sometimes a 470uf cap, and kinda unsure if the transformers were ever really proven guilty.
Can anyone help me finish my inverter diagnoses to determine what parts have failed,.. and hopefully why ?
Or do you think I should just replace the slave inverter board now ?

[rayrod81]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

In my experience if an inverter were bad (especially on an LG/Philips panel) the TV would power on but have no picture (sound would be good).

Anyway, I know this is not a Vizio but it may help. I recently had a Sharp Aquos LCD that did not power on but the error code it flashed said it had a 12V failure to the panel. I could not check any voltages because it would power on so I just checked for shorts and such. Power supply checked out fine, main board seemed fine but there was really no way to know. After an hour or so of trying to make sense of it I decided to unplug the LCD Controller (T-CON board) from the main board. Believe it or not the TV and backlight came to life and stayed on. I replaced the board and I am happy to say that it fixed the problem and I was soon watching TV as it was meant to be watched...in 1080P.

Not sure if this will work or not but based on the fact that there were squiggly lines on the display shortly before it went out it is probably the T-CON board. My advice is to unplug the T-Con board from the main board and then power on the set. If it turns on and stays on then just replace the board and you will have a working tv. The beauty of it is that it will only cost $40 to $60 in most cases.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Thanks Ray for your T-Con suggestion, but its no cigar in this case...no change no light up with it disconnected. I hadn't thought much about it but so appreciate any help that's offered.
Any more ideas for me ?
Anyone ?

[rayrod81]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

I just looked back through the post and noticed that the inverters are controlled by the T-Con which to me would mean that if the T-Con were bad then unplugging would not let the TV turn on anyway so my earlier suggestions are moot. It could still be bad but there would be no way to tell. I also noticed that the resistance you measured on the FETs of the inverters were much lower than they should be so I would guess that the IC on the slave is bad and possibly even on the master but I am not 100% positive. The main board could be the problem but I would say not mainly because the voltages you are measuring as out of spec could be pulled down by a bad board further down the line.

[PlainBill]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

The real problem is I don't have any information on the inverters currently in use on TVs. At one time the inverter was strictly a one-way setup. The main board sends signals to turn the inverter on and set the brightness. Now some of them appear to have a feedback line.

With the old style you could disconnect the inverter, turn on the TV, select a 'live' input, shine a light on the screen and if you saw the video (and heard the sound) you would have a good idea that everything was working except the inverter.

Without knowing if this model Vizio can and does monitor the health of the inverter it's impossible to do meaningful troubleshooting.

PlainBill

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Well King, If you dont find the problem within about a few weeks, I'll be moving up there to Hazelwood PA (near Homestead). I wouldn't mind helping you out with this. As for now, I'm trying to disect what was done already to really give me an idea of what to check next.

Some of these questions are going to be in random order so please be patient.

On one of your previous posts, you said that you had 24V on on inverter but only 1.4 on the other? Was this measured across one of the caps?

What are the cap's ratings on the inverter boards (uF and voltage)?

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Dgtech...then welcome 'back' to Steeler country...your not moving cause the Ravens lost are you ?
Thanks for working with me on this TV.
At my post #21 I wrote..."there is then 24 volts and 1.4v to master inverter, and 24v to slave inverter.." I meant I found both 24V and 1.4V into master, but only 24V to the Slave with no small voltages.
The caps on the inverters are all 4 Rubycon series ZLH 470uf x 35 v.

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

I moved to Baltimore from Pittsburgh 10 years ago for a job. Steeler fan for life here. I will be moving back - thank goodness.

I had a problem with a set like this before. The set looks at both master and slave together before it fires up so either of the two can cause the set to not work. I narrowed it down by comparing master to slave just as you are. In your case, the master is quite different from the slave. The resistance checks from before will not be an adequate guide for these boards. The one checked out good but the other... it has different parts. I feel good that the resistances were about the same though.

What I'd do next is CAREFULLY check and compare the voltages of the primary pins on the high voltage transformers. I dont remember what they should read but I'm pretty sure that the master should not be different of the voltages on the slave.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...reading transformer voltages

CAREFULLY...I think I better check how it is to be done. I have of course two high voltage transformers on each inverter board. On the primary side the legs are numbered 1, 2, 3 and on the secondary side 4 and 5. There is one leg on 1 and 3 and two soldered legs on each of 2, 4, and 5. How do you want me to read the voltages please?

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Use the negative (striped) side of the electrolytic capacitor on that board as ground - place the black lead of your meter. With the red, probe and compare the primary leads of the transformer. This test should show us something. Post the result of both transformers on the master and the slave.

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Yes for sure that tells us something is wrong ..all the primary leads on all 4 transformers have no juice, 0 volts...though each card is getting a 24VDC input.

[alexanna]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Yes for sure that tells us something is wrong ..all the primary leads on all 4 transformers have no juice, 0 volts...though each card is getting a 24VDC input.

I got to admit I haven't read the entire thread.
But a suggestion when you do this test, how about checking voltages as you power the set on?
Al

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Al...we did clear the power supply, see my post #7, have 5v standby then 12 and 24V comes on when kicked up.

BTW...> the replacement inverters should be here by Sat. I intend to test/compare them side by side with mine before I ever try them out on the set, and report back here. If you have suggestions on what all to test on these boards out of circuit please advise.
I have this sinking feeling though that something else is bad either on the mainboard or on the T-con panel.

[alexanna]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

My thoughts were is there a possibility that the primary positive voltage could be switched on, and the negative side pulsed when black lights are requested. If a fault was detected or back lights were requested off, the positive voltage switched off.
Al

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Throughout the power-up sequence of these types of sets, if certain voltages are not present, the set will stop the process dead in it's tracks. I had a set that showed voltages on one pair of transformers but not the other. In this case it showed that the problem was located on the board that did not show the voltages. In your case, like alexanna said, this may be switched on by the mainboard, fed by the power board.

Another check - I had a set where the processor would overheat. This would make the set work for a few seconds then whine and die out. This one however had a diagnostic code from the blinking LED on the front.
There is no blinking LED after the set powers up and fails?

[kingofcoins]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Al and Dgtech....thanks.
There is an code led in the extreme lower right side of front bezel, which is fed from the switch panel nearby. This led has never blinked to my knowledge and does not do so during the start up process.
Let me repeat here what physically happens on start: First the set doesn't respond to the remote or the start switch, so plug has to be plugged in and out. After its plugged in, the amber 'vizio' front light comes on, then a delay of 8-10 seconds occurs, then the double click from the power supply is heard, which fails to kick up supply but main volt is at 161v and 5vdc standby is present. Nothing else happens after this and set will not turnoff, except pull plug, or you can reset the sw1 switch on main board and cycle repeats. Now if then I press on switch, power supply will kick up after another 8-10 second wait to 400vdc, and the dc 5, 12 and 24v p/s outputs are present, and the 'vizio' light goes to white. But that is as far as it goes..no leds. no backlights, no gray, no flashes, no video with flashlight, and I've never heard the sound either.

[alexanna]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

I wish I knew a little more about televisions, all I can do is ask questions.
Is there any similarity at all with an inverter that’s in a LCD monitor?
Dose the television inverter use a back light on signal to request back lights? And is there a dim pin?
If it uses these voltages, would there be any benefit of checking them?
Al
Or maybe you already have?

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

What is the power board number? Sometimes different sets use the same power supply board, I can try to look up a different set's service manual.

Nevermind, I found it on one of the first pictures. (0500 0507 0330)

[Dgtech]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Just as a side note, I searched for the power board number and someone is selling one for about $70 on ebay.

[CrappyCap]

Re: Vizio VW42LFHDTV10...Brother Mikes TV...

Unless it's new or from reputable sellers with DOA warranty, I wouldn't trust fleabay used electronic stuff.
Man I hope my VO42LF isn't as troublesome as yours.