Vizio VL320M Component Level diagnostic ideas

[Fixinmytv]

I have a vizio VL320M, blank screen with no sound. When I try to turn it on the Vizio logo changes from amber to white, I can also turn it off, logo turns amber again. I'm not sure which component or board to replace. I'm open to ideas of what to test next.

I'm new to troubleshooting tv's. Read through some threads on the site and went through testing voltage regulators and came up with these voltages:

U2 Type 1117
2.032
3.267
5.067

U4 Type 1117
2.042
3.293
5.099

U5 Type 1117
1.32
2.6
5.063

U7 Type L 392 G1084
2.053
3.299 - Center tab - this one looks to be separated from board - should it be connected???
5.055

U8 Type 1117
0
1.260
3.264

U9 Type 1117
1.239
2.473
5.056

U11 Type 7805CT
1.756
0
0

Any other information I can provide please let me know, i'm happy to continue testing out my new multi meter! Here are the pics of the mainboard, power board and back side of tv with both boards.

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

The voltage regulators are labeled as "1117 Ɔ ¦¦ 9m f"
Not quite sure what each voltage regulator should show for input and output voltage.
How do I tell if it is supposed to be inputting or outputting 5v, 3.3v, 1.8v etc?

[Caleb]

Re: Vizio VL320M Component Level diagnostic ideas

The 1117 regulators should be 1.25v differential between your first reading and second
u4 =2.042+1.25=3.292 (your reading =3.293) so that one is good. I would concentrate on why the 7805ct has low input voltage, it should have about 7.5v on input and 5v out. Have you checked the onboard fuse?

[budm]

Re: Vizio VL320M Component Level diagnostic ideas

The 7805 is fed by 12VDC from the power supply board which is turned on when the main board sends the ps_on to turn on the power supply. So so you have PS_ON signal? Do you have >350VDC on the two legs of the main filter cap in the primary (HOT) side of the power supply-inverter combo board.
You should report the DC Voltage reading on those two white connectors on the power supply board when TV is OFF and when TV is turned ON.
http://www.shopjimmy.com/media/catal...7-0760-top.jpg

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

Attached pic of power supply connectors. Attached picture with voltage readings of power connectors with TV OFF and TV ON.

Caleb - On board fuse appears ok.

[tom66]

Re: Vizio VL320M Component Level diagnostic ideas

Ok, so you have PSON signal but no 12V/24V so time to investigate them.
What's the voltage measured across the 400/450V capacitor on the primary side? Be careful, high voltage...

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

Voltage on the big capacitor is 170v

[tom66]

Re: Vizio VL320M Component Level diagnostic ideas

OK, since it is not changing, time to look at the PFC circuit.

Good clear pictures of the top and bottom side of the power board are required, in focus and make text legible. If necessary break into multiple photos.

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

Top and bottom of power board pics.

[tom66]

Re: Vizio VL320M Component Level diagnostic ideas

OK, can you read the part number off IC821

and test the RED highlighted diodes for shorts and BLACK resistors for opens (should be near short)

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

I searched the board and didn't see the "IC821" I found C821 (Info printed on it "22J 1KV") and R821 (has "100" printed on it). I might be missing it, quite a few tiny numbers.

I found a more clear picture of bottom of power board on this site here, easier to read then my picture: http://www.shopjimmy.com/vizio-0500-...pply-unit.htm#

For the RED diodes-
I set my tester to Diode mode and check them with polarity going both ways. Top left one (D802) reads -.001v and next one (D803) read -.000v Multimeter beeped for both.

I also checked both with Ohm setting
D802 showed 0.6 ohms
D803 showed 0.5 ohms

BLACK Section-
Starting from left to right:
R814A 0.2 ohm
R814B 0.2 ohm
R814C 0.2 ohm
In Diode mode all 3 resistors showed 0.00v and multimeter beeped on all 3.

I'm Using a Fluke 117 Multimeter: http://en-us.fluke.com/products/digi...ultimeter.html

[Fixinmytv]

Re: Vizio VL320M Component Level diagnostic ideas

I double checked readings on the large capacitor. Getting 170.5V with TV off and 167.6v with TV on.

[Caleb]

Re: Vizio VL320M Component Level diagnostic ideas

You will need to lift one leg of all the diodes that tested shorted out of the board and see if they still test bad. Any that still test shorted will need replaced.

[budm]

Re: Vizio VL320M Component Level diagnostic ideas

The PFC IC is the one to the right of the black circle that TOM has marked.