vizio v0320e has sound but no backlight

[hawaiianeye]

everything seems to work fine, but i just dont have any backlights. the inverter is built into the power supply...so its either the inverter circuit or the backlights themselves. how do i tell for sure? can i test the voltage coming out of the inverter? it says high voltage so im scared...

[newtothis]

Re: vizio v0320e has sound but no backlight

Can even be the main.

Check voltage at ON/OFF on CN202 when in standby... Power unit on and check voltage, Post results

[budm]

Re: vizio v0320e has sound but no backlight

OK, for the inverter to function it needs:
1) PFC Voltage booster circuit, the DCV on the main filter cap should jump up from 160VDC to >360VDC when TV is powered on (PS-ON from main board) is present.
2) The inverter needs BL-ON signal from main board to turn on the inverter circuit.
3) It may or may not need the DIMMIMG control signal.
If you have all the above then you will have to narrow down to the inverter section in more details.

[hawaiianeye]

Re: vizio v0320e has sound but no backlight

http://www.ebay.com/itm/CCFL-Tester-...item3f33eb6b57
anyone ever tried one of these?
or a better one?
i like tools that make the job easier... will this work? or is it too cheap to be true?

[budm]

Re: vizio v0320e has sound but no backlight

I do not know if it can drive the lamps for 32" TV. Also if the lamp has bad connection at the end of the lamp, the lamp will still light up so it is not 100% for sure.

[hawaiianeye]

Re: vizio v0320e has sound but no backlight

the pfc voltage does jump up like its supposed to.
the mb does send the 5v BLON signal which was 0v before pressing power
also the dimm signal goes from 0 to .7v

[budm]

Re: vizio v0320e has sound but no backlight

So the PFC Voltage does stay >360VDC without dropping, right?

[budm]

Re: vizio v0320e has sound but no backlight

The next thing we need is the good clear and very well focused picture of the bottom side of the board so we can trace out the copper traces around the inverter section to see how it functions.

[hawaiianeye]

Re: vizio v0320e has sound but no backlight

i need to get my hands on a better camera, but i decided to "dummy test" the psu by putting 1k resistor between pson and 5vsb and also between BL-ON and 5vsb and the backlights came on just fine, and stayed on. this is all happening without the motherboard plugged in of course...
so now im thinking its the motherboard for some reason not sending the BL-ON signal when it's supposed to? can i make it BL always on and just bypass the mb signal?

[hawaiianeye]

Re: vizio v0320e has sound but no backlight

i just went to take pictures with my phone and found the power supply is now missing from this tv! if i remember correctly...i think i used it to get a 37" vizio working (certain 32, 37 and 42" vizio models seem to use this same psu or one just like it.) ive been fixing a lot of tvs by just buying up all the broken tvs and doing simple swapping of boards like this but i'm accumulating a bunch more that need board level repairs and a replacement board is cost prohibitive or just not available. so i will be needing this forum more and more. thank you for all you've done here!

...as for this tv, im going to get another PSU for it eventually, or swap the one back in from the 37" just to mess around (havent found a home for it yet) and then i will be back to the motherboard problem (if thats what it really is) so i would still appreciate your input on this thread.

ok i actually confirmed that this is the board i used in the V0370M to produce a working TV
nice that a 32" psu can power a 37" tv... i dont think this was the same PSU that was originally in the 37" though because in my notes it lists the PSU as 1PBC32HD/32FHD/B7FHD PLHL-T831A37FHD

so it basically has to be a motherboard problem... i know motherboards are usually harder to fix than psu's but is there anything i can try?

[budm]

Re: vizio v0320e has sound but no backlight

i need to get my hands on a better camera, but i decided to "dummy test" the psu by putting 1k resistor between pson and 5vsb and also between BL-ON and 5vsb and the backlights came on just fine, and stayed on. this is all happening without the motherboard plugged in of course...
so now im thinking its the motherboard for some reason not sending the BL-ON signal when it's supposed to? can i make it BL always on and just bypass the mb signal?

You can but the signal MUST BE DELAYED (about 1 second or more will be OK), you need to have PS-ON first so the power supply becomes stable before the heavy load (the inverter, which has very high in-rush current) is being turned on. You must also remove the BL-ON wire going back to the main board otherwise the main board will not allow the BL-ON signal to go HIGH.

[hawaiianeye]

Re: vizio v0320e has sound but no backlight

interesting... how do i introduce this 1 second delay?

[budm]

Re: vizio v0320e has sound but no backlight

What I would do next is to hook everything back together and remove the BL-ON wire so you can do the force on with resistor to see if everything else will function: sound, pictures, etc. You may have more than one problem on the main board.