Vizio E70-E3 will not power up

[busaboy]

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. It's hit or miss if they work.

[budm]

Re: Vizio E70-E3 will not power up

1) Please upload good clear pictures of the whole backside of the TV showing all the boards.
2) What is U201 P/N?
3) I would check the resistance of the output of that SMPS (U210) with ref. to Ground to see if it shows very low resistance (heavy load) or not.
4) What is the input Voltage feeding U201? 15VDC?

[busaboy]

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?

[budwich]

Re: Vizio E70-E3 will not power up

the vizios of this "type" (ie.70's) have panel / driver board issues that put "pressure" on the various supply voltages. As you have found, a short in the subtending circuit is the likely cause. In a lot of vizios, these usually take out a few FETs on the tcon.

do things change, if you disconnect the main to tcon cabling? what about disconnecting the tcon to panel cabling? Those are some of the tests to isolate where the shorts might exist.

[nomoresonys]

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?

If you have a mlcc reading short, remove it and check out of circuit if able.

[budm]

Re: Vizio E70-E3 will not power up

1) Disconnect all the cables to the main board and see if the shorts will go away or not.
2) MLCC failure mode is short circuit. We have seen lots of shorted out MLCC, there are many threads about shorted out MLCC.

[busaboy]

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 U201?

[nomoresonys]

Re: Vizio E70-E3 will not power up

Need to find out whats shorted, does anything else read short? do the pads of those caps read short?

[busaboy]

Re: Vizio E70-E3 will not power up

Need to find out whats shorted, does anything else read short? do the pads of those caps read short?

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.

[budm]

Re: Vizio E70-E3 will not power up

There will be other bypass caps (MLCC) that will be installed closed to the other IC's that are fed from that SMPS output, not just those two.

[busaboy]

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.

[dick_barton]

Re: Vizio E70-E3 will not power up

Welcome to the world of servicing to component level.

[R_J]

Re: Vizio E70-E3 will not power up

Have you tried using the E70-C3 service manual to see if it is close? The manual's schematic has a poor image but suggests that U201 might be the 3.3 volt supply and it supplies a lot, including the wifi module

[budm]

Re: Vizio E70-E3 will not power up

You can start checking all the MLCC and see how many show low resistance, then you have some idea how many of those circuit are fed by U201, it is part of component level troubleshooting, it is not easy locating shorts in parallel connected circuit.

[busaboy]

Re: Vizio E70-E3 will not power up

Welcome to the world of servicing to component level.

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...

[busaboy]

Re: Vizio E70-E3 will not power up

Have you tried using the E70-C3 service manual to see if it is close? The manual's schematic has a poor image but suggests that U201 might be the 3.3 volt supply and it supplies a lot, including the wifi module

Is this the manual you have?

[nomoresonys]

Re: Vizio E70-E3 will not power up

Ok, something made me think you were working on the tcon.

[busaboy]

Re: Vizio E70-E3 will not power up

Righto, I wouldn't wast hours on that tedious shit either, when the whole board is 15-20 bucks on ebay: https://www.ebay.com/sch/i.html?_fro...acat=0&_sop=15

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...

[nomoresonys]

Re: Vizio E70-E3 will not power up

I haven't gotten a bad one but I only deal with the ones with very good feedback.

[dick_barton]

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...

Unfortunately this is a reality that when you have a short circuit on a board it can be very difficult to find especially when service manuals are few and far between.

The short could be within the iC itself or as you have mentioned any electrolytic capacitor connected to the output pin. The only way to trace it is use the meter set to ohms to see what components are directly connected to the output pin of the IC and if necessary lift each one in turn.

Do you know what the output voltage should have been? R1 & R2 as per your data sheet page 2, could give the output voltage