Vizio E420-A0 fails to sustain power

TV will shutdown eventually on its own - longest "session" was longer than half a minute. In some instances, the TV never generates a backlighted Vizio logo and its power LED immediately starts to fade after going full bright white.

I can't replicate the exact behavior with regards to duration of the power-on state. Sometimes the TV fails to turn on. Sometimes its power LED will light and then fade. Other times the TV will behave as expected before generating the "No Signal" box and powering down with backlighting from power-on to sudden shutdown.

Someone else tested the voltages going from the power board to the video board, and I remember him saying the 5V standby was present. We did not test voltages going from the power board to the LCD strips.

Caps have not popped and at least one is by Chemicon.

We tested the power cord and got continuity even when twisting the cord (at both ends).

Friend who tested voltages from power board to video board was thinking there's something wrong with the keyboard controller board (POWER button/swtich, change input, menu navigation, etc.). He thought a bad power board would at least give consistent behavior, even if that behavior didn't lead to a working TV.

I am also aware of a bad EEPROMS, too. I am not sure how to test such an EEPROM:

What else should I examine and diagnose further?

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lkvee "He thought a bad power board would at least give consistent behavior, " not necessarily. This would totally depend on which part has failed. If it is a Mosfet or other power transistor it can do the shutdowns without consistency. It might help us if you can tell us where and what connector you measure and what voltages you got.

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Based on the description of your TV issue, I suggest replacing the EEPROM on the main board. When this IC reaches a high temperature its very likely to cause strange behaviors.

Also, the EEPROM is cost effective and it only requires of an average soldering skills.

Good luck with your Tv RepairJourney

Mike W

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