L37 HDTV 37" Vizio LCD TV No Picture,

[Glitcher]

Got a L37 HDTV Vizio. Plug in the power cable, the standby light turns on orange. Press the power button and standby light turns green but there's no picture, no backlight, not even a flicker.

Tried using a flashlight, clicked the menu button to look but I don't think I saw anything on the screen, I looked real hard but seems to be nothing. No visible bulging caps.

I haven't found any common problems with this model around. Anyone have any ideas?

[capkid]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Do you have sound? Have you checked your PSU output voltages?

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

I second that, check the ON/OFF (or ps_on) pin to see what DC voltage you are getting, and the 12v, 24v pins.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Not sure if I have sound since I have no idea which input it is on.

Theres 3 connectors on the PSU, the red wires go to each inverter board and the white wires go to the main board.
Measuring while pressing the power button to "on"

B - 3.03 V on both
A - 2.51 V on both

V1 - 5.27V
V2 - 0.83V
Remote - 2.95V

V3 - All measures 0 V <-- seems theres no voltages going to the inverter boards, what does this mean?

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

"Remote - 2.95V" That is the PS_ON signal, it is OK.
V3 is the 24VDC for inverter, which is 0V, bad.
V2 is the 12V for audio amplfiers, bad.
Both of above are bad.
I will disconnect the both V3 cables from the board and see if you will get the 24VDC back, if not, more trouble shooting in the power supply board will be required.
A and B are for BL_ON and Dimming signals for the inverter board, they are OK.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

So I removed the connectors to the inverter boards, and I measured the V3 pins on PSU and still get 0V.

So this an issue with the Power Supply?

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Yes, the 12v/24v power supply section is not working. Did you inspect the board real close to see if you locate any blown/burnt components?

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Nothing that's obviously seen. Guess I'll be checking components. Are there any particular?

[tom66]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

I'd also try starting PSU with a resistor and main board disconnected. 470 ohm resistor from 5V standby to REMOTE should do the job.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Soldered a 470 resistor from V1 Standby to REMOTE. I plug in the TV and get nothing. Power doesn't come on.

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

I did not think anything will happen since your PS_ON is good per your post:
Remote - 2.95V
You can check the DC voltage right at the two legs of the main 450VDC filter cap to see if the PFC Voltage booster is working or not, it should have about 160VDC in standby, and about 380V when TV is ON.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Measuring in standby I get 160.6V
Once I press power button and the standby led turns green and I'm getting 158.5V

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

OK, so the PFC Voltage booster is not working, that will cause the 12v/24v to start up.

[tom66]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

There is a common fault on this model with the PFC diode failing short which may cause your issue, fuse does not usually blow it just won't work.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Ah I see, so what exactly is the PFC voltage booster? Which is the PFC diode.

[tom66]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

PFC voltage booster boosts the 160V DC to 400V DC, for several reasons.

There will be a diode, mounted to a heatsink, which forms part of this booster -- it will be on the primary side, and likely near the big cap. Diodes are marked "Dnnn" where nnn is a number.

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

It looks like it has blown part in the PFC section.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

I think that burnt looking part was just old dried flux, gave it some cleaning and it still looks good.

Just checked the PFC diode and MOSFET out of circuit and they both checked out good...

[budm]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

Look at the P/N of that PFC IC, it may be just a bad PFC CHIP.

[Glitcher]

Re: L37 HDTV 37" Vizio LCD TV No Picture,

The Part Number is

N1653
PDHD

is there a way to test it