Im not sure if you ever ran the proper test on the PS_ON pin. (Budm kind of described what you were supposed to do wrong)
Your supposed to take a 20v DC measurement of that pin while it is off, then while pressing the power button, then after.
The key thing here is that if you see 3 volts while pressing the button then the mainboard is fine, and PSU is bad. If you dont see 3 volts when pressing the power button then either the mainboard or buttons are bad.
Fixed so far 12 lcd's , 1 plasmas, 5 monitors, 0 dlp's (plan to keep the dlps at 0). and 3 atx power supplies, and 2 motherboards.
Most likely it is the main board or button board. And pratically all vizios of this period have regulator issues. So testing all the regulators would be most wise. You might also want to see if your getting any voltages to the button board, at least 1 pin should have voltage vs ground. If your not getting any voltages to the button board then you know the main board is bad.
Fixed so far 12 lcd's , 1 plasmas, 5 monitors, 0 dlp's (plan to keep the dlps at 0). and 3 atx power supplies, and 2 motherboards.
Guess its repairable this person on ebay is asking for the old core back....(The core credit $50 will be refunded in full once you return your dud or defective part to us.) wish i knew how..?? Guess i'll break down and buy one...
I don't know if I can be anymore help, but we are a liquidator and have about 45 of these tv's with the same exact problem. I have many working tv's and maybe non working. Basically when cold they will turn on and freeze @ the vizio logo. After a bit of time they will stay amber and not turn on. Same problem on all tv's. I have replaced the mainboard with working boards and it works so its definitely something on the main board. Anyone have any ideas?!?
Bumping this one back to the top to see if anyone tracked down a solution. Have a slightly different model, but exact same symptom (i.e. 5V to main board, but no 3V signal back to the power supply (when power button depressed)). I did notice that the power button is getting 3v, but drops to 1.8 (on both poles) when depressed (not sure if this is significant, or normal?). I can get the power supply to turn on (i.e. I get 12v out of it), when I do the AAx2 battery trick on the PSON terminal....so I'm nearly positive it's a mainboard issue.
F1 is 5.3V on both ends
F2 is 0 on both
Both fuses have continuity
There is also a regulator (I think) labelled TU8, but all three legs of it are 0 volts.
This is a Vizio E371VL, fwiw.
Any help from the experts would be much appreciated.
Edit: little additional information....this TV will occasionally turn on and work perfectly (will run for days without issue, if left on)...until it's shut off, then will not restart. No signs of any visibly damaged components or solder joints.
wierd... had the main board out for a while and decided to put it back in so i could put the tv away and hit the power button and the Tv came on...had it on for about 20 to 25 minutes ..turned it off and it never came back on just the amber vizio light..?
Here's what I've been finding with these boards when you come to the point that you're at a total loss for explanation. I studied some videos of modern board manufacturing which; immediately raised some legitimate concerns. These surface mount boards are made using a solder paste overlay technique and after watching the system in action, I asked myself how accurate the overlay would allow paste to flow and drop down on the boards after becoming tacky from a day's production. If you have a magnifying helmet like mine; you can see close up that several surface mount capacitors on the top side especially, and bottom side also, either will have little to no solder on one side or be cracked at the bottom where they lay flat on the board. This board is all about signaling so the slightest loss to the processor can cause the condition you have described. On another note, I'm seeing symptoms of video freezing with these boards. Two things here, either the video chip needs a reflow or there has been a small string of blown solder that may have joined a couple pins during the cooling process at the mfg plant. This can also occur across the pins of the ribbon cable sockets. These defects can also result in corruption of the eeprom ic from data transfer loss. I proved this recently by soldering up the components on a bad board, switching eeproms with the same model and resulted with two working sets. All these problems are inter related to the solder work. That being said; keep your soldering iron heat at a reasonable temp when re-soldering surface mount components. Baking the board may not work because of a lack of enough solder where needed.
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