L37 HDTV 37" Vizio LCD TV No Picture,

[budm]

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

You can take resistance readings of all the pins against the Ground pin (pin 6) and report the readings.

[Glitcher]

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

1: 868 ohms
2: 870 ohms
3: 871 ohms
4: 850 ohms
5: 866 ohms
7: 661 ohms
8: 600 ohms

[budm]

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

Those reading seems low, most of the pins (1, 2, 3, 4, 5, 8) have Zener protection Diodes I would expect it toe read hi resistance when the probes are reversed. You can see those Zener Diodes in the spec sheet.
What DC voltage do you get between pin8 (VCC) and Ground pin 6? Be real careful since you will be working in the HOT Deadly side of the circuit.

[Glitcher]

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

Oh I was measuring them using diode mode on "2K" range. If I reverse the probes, black on pin 6 while probing with red, I'm getting all "1" out of range.

[budm]

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

OK, that is why it is showing the Vf of the Zener Diode. Check the DC voltages next (TV on), use pin 6 as the ground pin for the black meter probe. Show the reading of all the pins.

[Glitcher]

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

Voltages: While TV is on

1: 0.906V
2: 0.022V
3: 4.22V
4: -0.008V
5: 0.001V
7: 0.001V
8: 0.125V

[budm]

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

OK, it is not getting the VCC on pin8 to run it, that voltage is fed through a switched transistor (this transistor is turn on when it gets the ps_on signal), the voltage is generated from the AUX winding of the standby power supply. This is getting deep to troubleshoot since you will have to trace out the connection next by following the VCC pin to see where it goes to.
Replacement is $44 from shojimmy.
http://www.shopjimmy.com/catalogsear...zio+l37hdtv10a

[tom66]

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

Does PSU have a DPS number? I have some schematics for those.

[Glitcher]

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

0500-0502-0121 is the serial number on the label.
On the board it
Model: 0569D03250

[tom66]

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

No schematic unfortunately, appears to be Vizio semi-custom.

[Glitcher]

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

Just bought a used PSU from ebay for $25, and the TV is working perfectly now. I'll be troubleshooting and comparing the components of both boards to see if I can find the orginalfault.

[SgtRock]

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

Greetings BadCappers:

--I realize you have already solved the problem, but you said you were going to keep checking components. See the circled in red area. Does that look to you like an unsoldered component?

"When the juice is t'drinkin' and the good times is t'jumpin'"
Lord Buckley 1906 - 1960

Best Regards
Clear Ether

[Glitcher]

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

Ah yes that was when I was testing the diodes. Well seems I can't find anything on the original problem. Checked every component around the pfc voltage booster and there were no differences... I did find one area with a noticeable difference in resistance between the two, but testing the components around it, I couldn't find anything seemingly bad.

[budm]

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

The hard part will be tracing out where the b+ for the VCC pin of the PFC goes too.