Vizio VX32L HDTV10A - No backligh

[jarl]

Re: Vizio VX32L HDTV10A - No backligh

Update: I was following the link on the thread you suggested, and there's an schematic on it using the capacitor in parallel with the transformer. I followed Toasty's suggestions instead (on one of his pictures it looks like the capacitor is in series), and I was able to ring the transformer on an old ATX power supply. However, the <expletive> transformers on the TV won't ring

I guess I'll start looking for the inverter...

[Toasty]

Re: Vizio VX32L HDTV10A - No backligh

Assuming 0.5vp-p square wave calibration signal:

Calibration output, scope lead, .05uf disc cap across coil.

Scope to 50mv, .1ms sweep. If no ring, try isolating cal. output with a .002uf disc cap in line.

You should get a nice sine wave "pyramid on its side" type of trace.
.
.
.
If it doesn't do that and looks like it only does one or 2 swings p-p, then its like shorted.

Toast

See the scope pictures two posts down from that:
https://www.badcaps.net/forum/showpo...1&postcount=30

The scope, signal, and cap all go across the winding you're testing. I said to use a cap in series on the signal input

The 2.2uF cap is too large in value. Look for a .01uF ceramic cap or thereabouts.

Test signal is the scope calibration output. Mine is 1kHz @ 0.5v p-p

If any of the windings are connected to the circuit, the test may fail as they could have a low resistance path and appear shorted. That will damp the signal and not ring the winding. Best to remove the trafo and test independently.

Confirm you are actually across a winding with an ohmmeter. Some trafos have extra legs that are used for mounting.

[Toasty]

Re: Vizio VX32L HDTV10A - No backligh

Above got posted incomplete...

>>I said to use a cap in series on the signal input <<

... if no ring.

Stay with small value caps. Less than 0.1uF. Voltage is not important as you are using very low voltages at input. Note that I only used a .01uF cap via the sub box.

Looking at the linked post #30 picture of my Q&D setup:

Left: Black connections are from scope ground strap and cap substitution box
Right: Red from cap sub box, scope probe, and cap in series with scope calibration output on the green jumper wire.

[griffey_mojo]

Re: Vizio VX32L HDTV10A - No backligh

Jarl -

Did you ever get this TV to work again?

My VX32L has the same 'symptoms' as your were describing in your original post.

I have changed my Master Invertor board (didn't fix the problem) and I've also changed the LCD controller (didn't fix the problem).

I have been buying used parts off of Ebay hoping for a quick fix...but to no avail yet...I haven't given up yet.

Badcaps Vets....I have no expierence with electronics...but I do consider myself handy.

Thanks,

Nate

[jarl]

Re: Vizio VX32L HDTV10A - No backligh

Hello all,

I finally got an inverter board from Ebay, replaced it and the TV seems to be working fine. EXCEPT:

It's evident the 2nd bulb from the top of the screen is not lighting as much as the others. Not a show stopper, but it got me thinking... Can a transformer get damaged by a failing bulb, or is it more plausible the dying transformer may have damaged the bulb somewhat? Is it too hard to replace a bulb?

One interesting thing is that if you turn down the brightness of the screen below a certain point the screen starts to flicker and finally turns off. When I turned the brightness up (blindly) the TV didn't started working until I turned it off and back on. My assumption is that the darker (damaged) bulb can't keep it up when the brightness goes down too much. (could this be your case as well, Nate?)

Nate: the other people who have helped me in this thread are great, and they probably can help you a lot more than I can. However, I would slow down a bit before changing every single part on the TV. If I understand correctly, you already changed two of the three main PCBs. Are you sure the power supply is producing the right voltages?

[PlainBill]

Re: Vizio VX32L HDTV10A - No backligh

Hello all,

I finally got an inverter board from Ebay, replaced it and the TV seems to be working fine. EXCEPT:

It's evident the 2nd bulb from the top of the screen is not lighting as much as the others. Not a show stopper, but it got me thinking... Can a transformer get damaged by a failing bulb, or is it more plausible the dying transformer may have damaged the bulb somewhat? Is it too hard to replace a bulb?

One interesting thing is that if you turn down the brightness of the screen below a certain point the screen starts to flicker and finally turns off. When I turned the brightness up (blindly) the TV didn't started working until I turned it off and back on. My assumption is that the darker (damaged) bulb can't keep it up when the brightness goes down too much. (could this be your case as well, Nate?)

Nate: the other people who have helped me in this thread are great, and they probably can help you a lot more than I can. However, I would slow down a bit before changing every single part on the TV. If I understand correctly, you already changed two of the three main PCBs. Are you sure the power supply is producing the right voltages?

There are three possible causes for this. A defective transformer (shorted turns), a wiring problem between the inverter and the CCFL, or the CCFL itself.

Depending on the layout, it might be possible to swap cables - connect the top lamp to the #2 socket, connect the #2 lamp to the top socket. If the top lamp is now the dim one, the problem is on the inverter. If the #2 lamp is still the dim one, it's the lamp or the wiring.

If that is not possible, measure the resistances of all secondaries on the transformers. If the one driving lamp #2 is different than the rest, the transformer is bad - replace it with one from the old inverter.

PlainBill