vizio vp50

[heavymachines]

Re: vizio vp50

Check all board fuses.
Inspect the Va transformer area (third from top.)
Consider replacement of TL431 feedback IC.

i spent good amount of time trying to find this TL431 no avail only thing marked T at all is the transformers themselves..when you say IC you mean the chips with legs correct? Is there anyway to test this IC before i go buying one?


All fuses are good one of first things i did when i opened the set up also want to note to you i found a bad capacitor hiding under the frame and heat sink of the y-sustin
C5709
i changed that, of course changes nothing yet...(yes it name brand from digikey panasonic fm series had laying around)...


Also looking up best way to test the buffers with dmm....if you know a good way please do tell.... anyhow i found this

http://blog.coppelltvrepair.com/2010...er-boards.html and my buffer model numbers almost match but not quite and it looks practically identical except there is no heat sink on the buffer IC....

from what i can gather it don't look good for me, i will recheck when i am more awake but it looks i may have 2 buffers that is shorted, maybe i should take pic's of me testing them? and you can confirm?

[tom66]

Re: vizio vp50

Buffers don't cause lack of Va.

Va is the horizontal electrode voltage, not used by Y-sustain or Z-sustain (just passes through) basically, it writes the data to the screen (the video image) using the COF chips on the bottom of the panel. In very rare cases these can short but this would cause 0V for Va not the odd voltage.

On this chassis it might be a KIA431 IC. I understand that those particular ICs have lots of problems with dropping their reference voltage over time.

[heavymachines]

Re: vizio vp50

just wondering if you seen post #20? what you think of those resistors?

[tom66]

Re: vizio vp50

They look a little toasty. What do they measure?

[heavymachines]

Re: vizio vp50

Buffers don't cause lack of Va.

Va is the horizontal electrode voltage, not used by Y-sustain or Z-sustain (just passes through) basically, it writes the data to the screen (the video image) using the COF chips on the bottom of the panel. In very rare cases these can short but this would cause 0V for Va not the odd voltage.

On this chassis it might be a KIA431 IC. I understand that those particular ICs have lots of problems with dropping their reference voltage over time.

Ahh good to know thanks....anyhow lol i can't find KIA431...
here is what i can find.....that has KIA in it...

U973----KIA358P.....735..has 8 pins
U971----KIA339P.....731..has14pins
U112----KIA7812A...PI 743...has 3 pins think it terminal voltage regulator
U111----same as U112 right next to each other

Seems to be all i can find on this power board that has KIA in it rest is either KA or Fairchild or ON Semiconductor and a couple i have no clue but don't think it has anything to do with what we are trying to solve....

Thanks for the help on this beast....

[tom66]

Re: vizio vp50

OK, anything at all with 431?
Looks like this:

[heavymachines]

Re: vizio vp50

They look a little toasty. What do they measure?

in circuit both measures 05.5 ohms in dmm set to 200ohm range
out of circuit measures 10.9 both measure same

[heavymachines]

Re: vizio vp50

OK, anything at all with 431?
Looks like this:

U451...KA431AZ...H42 closest i got the rest is different numbers and some others look close but has flat backsides instead of half moon shape "er round backsides"....sorry bout that

[tom66]

Re: vizio vp50

KA431 is good. Near the Va section? Between pins 1 and 3 you should measure approx 2.5V if it is working.


Since both of those resistors measure the same, it's very unlikely they've failed equally. They are probably 10 ohm resistors, two in parallel to make 5 ohms. The dark colouring is probably just the body colour.

[heavymachines]

Re: vizio vp50

KA431 is good. Near the Va section? Between pins 1 and 3 you should measure approx 2.5V if it is working.


Since both of those resistors measure the same, it's very unlikely they've failed equally. They are probably 10 ohm resistors, two in parallel to make 5 ohms. The dark colouring is probably just the body colour.

here where it located can't see in image but behind the transformer.....

[tom66]

Re: vizio vp50

That is most likely for Vs, especially if Vs adjustment is near there.
See attachment.

[heavymachines]

Re: vizio vp50

Its VA pot, the VS is almost at top on left side of board

[tom66]

Re: vizio vp50

We need to be looking for KA431 near Va pot.
Vs is good as far as you have measured.

[heavymachines]

Re: vizio vp50

We need to be looking for KA431 near Va pot.
Vs is good as far as you have measured.

okay i found another one same exact part number and it near va pot will measure stay tuned

[tom66]

Re: vizio vp50

That may be for the main/standby supply.

[heavymachines]

Re: vizio vp50

okay i found another one same exact part number and it near va pot will measure stay tuned

okay the one behind transformer at top by VS pot measures 8.7 volts



the one by the VA pot measures 1.3 volts....think we are getting somewhere..

[tom66]

Re: vizio vp50

Bottom of board pic necessary to determine if it is for Va or not.

[heavymachines]

Re: vizio vp50

Here it is

[heavymachines]

Re: vizio vp50

my bad here is more

[heavymachines]

Re: vizio vp50

more