Vizio VL370m LCD

[Hallatauer]

First, thanks to all the support the forum members who help everyone with their tv issues.

My issue. Vizio VL370M LCD tv. Last night while watching tv, it gave a soft click and lost the picture. We have sound but no display. Flashlight test shows there is a picture but no back lighting.

Took the back off and looked around for anything obvious, there wasn't. Caps look fine physically. Time to pull out my multimeter. I use it on troubling shooting automotive wiring, specifically older BMW's. Not the same as a tv but the concepts are the same.

Fuse has continuity.
The power board has the connector with three 5VSB (standby), five SGND, three 12V, and one PS_ON. SGND is ground?
With the power plug attached and tv off, I get 5.23V from the three 5VSB and nothing on the others.

Power on, 5VSB's are 5.20V. The 12V are 12.26V and PS_ON 2.26V.
Looks good to me... is PS_ON 2.26V within spec?

The next connector over, when off, no voltage at any pin. With power on:
ACD 0, Status 0, DCR 0, VBRA 0, On/Off Inverter 2.26V, DIM 3.05V.
Don't know if this is as it should be?

Next step is inverter? Not sure how or where to test it.

Thanks.

[dskall]

Re: Vizio VL370m LCD

Do you get a flash on screen after you press power button?

[budm]

Re: Vizio VL370m LCD

Please up load good clear pictures of the whole back side of the TV showing all the boards.

[Hallatauer]

Re: Vizio VL370m LCD

dskall.. no flash...

Budm... photos

[Hallatauer]

Re: Vizio VL370m LCD

Looking thru Budm's troubleshooting guide.. where do I find the 24vdc connection to the inverter board? Since I have no backlighting, this looks like the possible failure point to check next.

[vinceroger69]

Re: Vizio VL370m LCD

the invertors are built on to the power supply you can see the 2 black transfomers with the wires going to the ccfl tubes (dont try to measure these as really high voltage) hopefully budm or a more experienced member will advise you what you can check next as ive never worked on this type of power supply.

in a really dark room when you first power on the set do you get any flash on the screen it may be quick one too two seconds

[Hallatauer]

Re: Vizio VL370m LCD

vinceroger.. no flash... nada. Budm's Troubleshooting Guide says to check the 24vdc going to the inverters... don't know where to check for that.

[vinceroger69]

Re: Vizio VL370m LCD

budms guide covers loads of lcd sets yours has the inverters built onto the psu the other sets have a seperate board that uses 24v so does not apply to your set

maybe budm can confirm is your voltages are correct
With power on:
ACD 0, Status 0, DCR 0, VBRA 0, On/Off Inverter 2.26V, DIM 3.05V.


im not sure what the first 4 that are reading 0 volts are for

can you also take a picture of the back of the power supply thanks

[dick_barton]

Re: Vizio VL370m LCD

Can you post a picture of the bottom of the power supply board as well focused as possible.

[Andrew F. Ali]

Re: Vizio VL370m LCD

OK...So we have to determine if we have 24Vdc produced by the main Secondary supply and if we do is it going to the Inverter circuitry on the Primary side of the HV Transformers.....Test the HV Transformers to see if their resistance readings are approx. the same for both and to determine if the CCFLs are good.

[vinceroger69]

Re: Vizio VL370m LCD

OK...So we have to determine if we have 24Vdc produced by the main Secondary supply and if we do is it going to the Inverter circuitry on the Primary side of the HV Transformers.....Test the HV Transformers to see if their resistance readings are approx. the same for both and to determine if the CCFLs are good.

i didnt realise these boards had a 24v section, (so in post 8 please ignore my comment regarding the 24v question) i was trying to work out what section provided the voltage too the transformers.
some clear pictures of the psu on shopjimmy
http://www.shopjimmy.com/vizio-0500-...pply-unit.htm#

[budm]

Re: Vizio VL370m LCD

Skip this one, see the next post.

[budm]

Re: Vizio VL370m LCD

This is power supply/inverter combo board so the inverter circuit in this board does not run from 24V, it runs on the PFC Boosted Voltage of around 380~400VDC
The inverter transformers are driven by MOSFET Q700, 708.
So do you have 380~400VDC between the two legs of the main filter cap? The inverter needs that to run.
The good lamps should at least flash on for seconds if the inverter circuit is active at all since it almost impossible to have both transformers and all the lamps go bad at the same time, the circuit will try to fire up and if it dectects bad lamps, bad transformer (draw too much current, or no high Voltage out out from one of the two transformers) then the circuit will shutdown. It has to try first BEFORE it can finds out if there is/are problem/s or not.
Check the DC blocker/coupling caps C713, C714 capacitance for the inverter transformers.
BTW, BL-ON is present for sure?
Also check solder joints around those two MOSFETs, diodes, inverter transformer legs, etc of the inverter section.