Re: Vizio E70-E3 will not power up
Thanks. Unfortunately with the shield soldered on the WiFi module and the way the module was attached to the main PCB, it was difficult to locate the short.
I did find differences on my PCB. Q201 is a BJT versus a MOSFET in the schematics. I couldn't find Q202.
I wish I still had a special tester I made for finding shorts. It used a 10MHz oscillator feeding a 50 Ohm power buffer that fed a BNC connector. The BNC also fed a NE604 FM demodulator IC. I used the NE604 RSSI output (log amplifier), to drive a...
busaboy
Member
Last Activity: 10-19-2023, 03:35 PM
Joined: 12-17-2015
Location: Satellite Bch, FL
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Last edited by busaboy; 05-26-2020, 12:00 PM. -
Re: Vizio E70-E3 will not power up
I traced the problem to the WiFi module due to the heat it was giving off from forcing current into the shorted MLCC cap(s). It must have gotten pretty hot inside the shield.
I replaced the 2 MLCC caps in the WiFi module and 2 MLCC on the output of L201 with cheap two 10uF axial aluminum electrolytic caps. The 2 MLCC caps on the output of L201 were OK but I didn't want to reuse them. Desoldering the shield off the WiFi module took a lot of heat from a 80 watt soldering iron. I didn't reattach it.
I cannot say which...Leave a comment:
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Re: Vizio E70-E3 will not power up
I injected DC into the "output" of L201 because it looked like too much of a PITA to remove. I started with one power supply, then a bigger one and then a much bigger one (300watt). I injected 1 volts and then upped it to 2 volts. The circuit drew 6 amps with the PS on current limit. It took a lot of feeling with my hands but the problem seems to be a short inside the FOXCONN WiFi module. I will pull the shield off and see if I can fix it. Probably a bad cap in the module....Leave a comment:
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Re: Vizio E70-E3 will not power up
I measure a "short" with a DVM at the switcher output capacitors. I'm guessing this is one of the TPs you mention. The text is so distorted every TP seems to be "TP215" :-(.
PS
I have an extensive electronics lab at my house. I can pretty much test anything. Attached is a few shots. Two guys from GE testing a digital radio for a locomotive......Last edited by busaboy; 05-26-2020, 09:20 AM.Leave a comment:
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Re: Vizio E70-E3 will not power up
I found V_3.3SB also feeds the IC on page 60. Going to pull L201 and apply DC.
Do you have a better copy of the manual?...Leave a comment:
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Re: Vizio E70-E3 will not power up
From page 49 of the manual the regulators output is 3.39volts. Unfortunately the text is very distorted so I cannot tell how many parts are fed by 3.39volts. 3.39volts feeds a FET switch and yields 3.3volts. I'm going to pull the board, remove L201, back-feed 3 volts and see if I can get a cap to heat up or pop. Since it's not my TV and my buddy is unwilling to spend $100 for a used replacement, I'm gonna get medieval on the board.Leave a comment:
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Re: Vizio E70-E3 will not power up
If it was the T-con board I would have bought it. It's the main/CPU board. As far as eBay, I and my friends haven't had the best luck buying boards from there. At best it's 50%. It's pretty funny that every board on eBay came from a TV with a busted screen......Leave a comment:
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Re: Vizio E70-E3 will not power up
Is this the manual you have?...Last edited by busaboy; 05-24-2020, 09:29 PM.Leave a comment:
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Re: Vizio E70-E3 will not power up
Really don't want to pull a bunch of 0603 caps off a board if I don't have too. They are all super glued so it is PITA. Was hoping someone had a schematic to speed the process. A buddy asking me to fix his TV is not my favorite thing to do......Last edited by busaboy; 05-24-2020, 09:35 PM.Leave a comment:
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Re: Vizio E70-E3 will not power up
From what I can see there are 5 switching regulators on the board. It would help to know what circuits are powered by U201 so I'm not measuring every IC on the board. Finding the data sheet for every IC so I know the power pins is tough.Leave a comment:
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Re: Vizio E70-E3 will not power up
With the caps removed, I'm still measuring a short at the output of the switcher inductor. Something else on the power feed is bad. I'm unsure what else hangs off this power feed....Leave a comment:
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Re: Vizio E70-E3 will not power up
I removed both MLCC caps, C2012 and C2013 and neither was shorted. Disconnected TCON and all other connectors and still something is loading down the switching regulator U201. I didn't replace C2012 and C2013 but the output of inductor L201 is "squashed". The input to inductor L201 is a 16 volt pulse, 1uS wide. The output is a squashed, 1uS wide pulse. I assume the regulator is in current limit mode. I will replace C2012 and C2013 once I find the "short".
Can anyone tell me what other circuits are hanging off ...Last edited by busaboy; 05-23-2020, 09:26 AM.Leave a comment:
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Re: Vizio E70-E3 will not power up
U201 is a FR9889 switching regulator. The CPU board has a number of similar regulator ICs from the same company. It seems like something is loading the output down. The input is +16.4 volts and the output after the inductor is 0.06 volts. The output caps look to be ceramic, C2012 and C2013. There could be an electrolytic somewhere as well. I measured the output resistance and there seems to be a dead short. I was hoping to get a schematic to see what is hanging off the output. Have you had ceramic MLCC caps short?...Last edited by busaboy; 05-22-2020, 08:23 AM.Leave a comment:
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Vizio E70-E3 will not power up
Trying to fix Vizio E70-E3. +16VS from the power supply is getting to the CPU/motherboard but I am not seeing any output from switching reg IC U201. No power is going to the PW Key switch. The output of U201 is a narrow pulse feeding inductor L201. U201 seems to be in an over current situation and inductor L201 is "singing". The DC output of L201 to the filter caps is very low.
Anyone got an idea what might be causing the DC voltage from U201 to be low? I stole the CPU pic from another post from March for the same TV. I really don't want to buy a used CPU board from eBay....Last edited by busaboy; 05-21-2020, 09:01 PM. -
Re: New Members - please post your introductions here
Been a member for 5 years. I guess I never posted. Been repairing stuff since the 60's and designing electronics since the 70's.Leave a comment:
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