Vizio M420NV no backlight

[budm]

Re: Vizio M420NV no backlight

BTW, if you check the resistance between GND and the BL-ON pin at the main board, does it show low resistance?

[sricechex]

Re: Vizio M420NV no backlight

Ooo, that makes sense. You've done this before, haven't you?

From the information I have, is there any reason to suspect any particular board components? For example, in that functions are good, but effective BL_ON voltage is low, is there reason to explore regulators vs. eeprom or fuses?
I certainly appreciate what you're suggesting, Budm. That method of repair certainly would be cheaper than all else, and...why not do that.

[budm]

Re: Vizio M420NV no backlight

It can be that the switched Transistor that is connected to the BL-ON pin on the main board may be bad that is why I have you check the resistance between GND and the BL-ON pin of the main board.

[sricechex]

Re: Vizio M420NV no backlight

GND to BL_ON = 0.6kohm

[budm]

Re: Vizio M420NV no backlight

That is 600 Ohms! it should be in 1000's of Ohms.
You test this with nothing connected to the main board, correct?

[sricechex]

Re: Vizio M420NV no backlight

Yes, Sir; disconnected all cables from MB. still mounted on chassis. 0.62k

[budm]

Re: Vizio M420NV no backlight

Well, you need to see where the trace from that BL-ON pin goes to.

[sricechex]

Re: Vizio M420NV no backlight

Will do. May take some time to get to it... Got a fussy baby occupying my attention.

[sricechex]

Re: Vizio M420NV no backlight

Update: in attempts to evaluate the mainboard, I found that
1: given my knowledge level, and lack of detailed schematic, I had no reasonable hope of identifying the failed component, and
2: if the component was identified, successfully replacing it on the board has a much lower chance of success, and likely much higher cost than piggybacking another power signal as budm suggests.

I cut the BL_ON, and jumped it to the REMOTE ON signal with the 1k. Pin 11, 3.2v when powered on.

I really appreciate your help, guys. I hope this can help someone else without a similar problem.