Have a vizio vx 42l on the bench. amber light only no power up have my standby 5vdc and my 3.3vdc power button is sending a high pulse to the main mod but i dont get pson to the power supply mod suspect main mod defective but not sure . ps all fuse's are good on power supply mod as well as main mod and back light mod.

Mostly the problem is the main board.

There's no 3.2 v off U33 (main module) I wasn't able to find AMC1117, So I used a Radio shack LM317T. this supplies 3.3v to video processor and associated circuit. this won't blow fuse.

Amber light on means standby voltage is high. IF amber light does not go white when power button is pushed the its one of two things.
A. No power on command from main board. Usually labeled PS-On. Should go high from 3.3v or maybe 5volts. If not present Main is defective.

B. If the ps-on line is going high then your problem is a defective power supply.

your Main board went bad, common issue with these units. Need to be replaced, in tv land it called main board in computer world mother board. your unit has only two boards power board and that is good cause you get a amber to green to amber led. good luck Vizio field tech

is there any sound? Did you order the exact main board part # as your original board?

It could be the main board. The main board controls the standby light on the front of the set. Check and verify that your 5vdc standby voltage is working. Next, I would check the "on" or "ps on" input on the power supply board. When you turn the set on (either my side buttons or remote) the main board should send a 3.3vdc signal into the "on" terminal on the power supply. This "on" signal from the main board turns on the other half of the power supply thus turning on your set. If you are not getting this signal from the main board, I would suspect the main board. To test your power supply, you can simply put a jumper from 5vdc to the "on" terminal on the power supply. Your 12vdc, and 24vdc power supplies should then become active.

Hello,

The power supply converts the 120/230vac 50/60Hz into DC, then the high frequency (50~100kHz) switching circuits convert it back to AC but at high frequency which allows the power supply to use smaller and much lighter weight transformers (Ferrite core instead of heavy iron core), then this high frequency AC voltage is fed to the rectifier Diodes to get the DC output and filtered by DC filter capacitors that must have low ESR (Equivalent Series Resistance), if general purpose electrolytic caps are use, they will fail within a year or less due to high ESR.

The power supply has Standby 5vdc (5VSB, this is a MUST have before anything else will work, when this voltage is not present, there will be no any indicator light on the front panel) which is always on the minute the TV is plugged into the AC outlet, so it is on 24/7 and that is why the power supply will fail even though you may use the a TV not very often. It will see all the voltage spikes and surges 24/7.
This 5vdc is used to power the Processor and the Infrared remote receiver module which will be waiting for the command from the remote control or from the power switch, when the Power on command is received, the Processor will send the turn on signal (3.3~5vdc) to the power supply module (PSON pin) to the switch on the main 5vdc for the rest of the logic and Tuner circuits, 12~16vdc for the sound amplifiers (mostly Class D amplifier for efficiency and small size) and for the T-CON board (interface board between the LCD panel, some T-CON uses 5vdc, and the Logic board), and 24vdc for the Back lights inverter board (if there is no 24vdc then no back light).
Common failures:
Blown main AC fuse due to shorted out Diodes, transistors.
Bad capacitors leaking or bulging tops:
Shorted Diodes, transistors in the DC output side.

Hope this will help in solving the problem, and do take care in handling the television, because it contains high voltage

That means the 5vdc standby supply is not working, you can try to fix it or buy a replacement.
If you are going to DIY and have proper tools, electronics knowledge, and know safety precaution then please read on:

Please see my basic troubleshooting guide here:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide

Failed TV and Monitors: http://s807.photobucket.com/home/budm/allalbums

http://en.wikipedia.org/wiki/Capacitor_plague

Parts: www.shopjimmy.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.

It sounds like the 5vdc standby circuit is still working, that is why the main fuse is still good but you may have bad 24vdc power supply, look real close again for blown transistors or IC on the power supply board, but it can also be the backlight inverter circuit boards that blew up also. Look here to see what good parts look like: http://www.shopjimmy.com/catalogsearch/result/?q=Vizio+VX37L+
Please post back what you find.

Check all electrical connections. If standby light is off when plugged in, probably needs Power Supply board replaced. If standby light is on (Orange/Amber color) may need Power Supply board and or Main Board. If set was shutting down on it's own leading up to it not powering on at all, may need Main Board, and possibly Power Board as well. If standby light has changed from Orange/Amber color to Green, the set IS powered on, and you have an issue other than power.