Vizio E400i-B2 missing stand-by voltage

[DXseekerMO]

I picked up this Vizio E400i-B2 with no stand-by light and diagnosed it with missing stand-by voltage. I found a Power Supply at ShopJimmy, installed it but it didn't work properly. SJ refunded the transaction and did not ask me to send the board back.

So I took some voltage readings upon the original board. Here's what I found:

Main caps have 169.9v

AC detect voltage is 1.3v

None of the MOSFETS appear to be short.

The opto (IC106) that appears to have something to do with stand-by voltage has 3.0 volts on terminal 1 and 1.0 volts on terminal 2 on the hot side of the PS. No voltage is present on the cold side of IC106. Terminal 4 of IC106 traces to Q206 which traces to both stand-by terminals via the center pin. I'm not sure if this has anything to do with the problem.

I'd like some help diagnosing the problem please.

[Storyteller12]

Re: Vizio E400i-B2 missing stand-by voltage

Could be the main board since you say there is 3v present.

The main board is what controls the standby light.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

Could be the main board since you say there is 3v present.

The main board is what controls the standby light.

Thanks for the reply.

With the SJ power supply installed I get a stand-by light. The problem with the SJ PS is it makes a buzzing noise when the TV is plugged in. Turn the TV on and when a load is applied to it by the screen the buzzing on the PS gets worse and the TV shuts off. Again this happens with the SJ power supply, and not the original PS that is the subject of this thread.

The problem is not the Main Board.

[Storyteller12]

Re: Vizio E400i-B2 missing stand-by voltage

Did all the voltages on the sj power supply read according to the legend? Did any fluctuate?
If all is good the main board could be what causing the buzzing on the power supply. Also need to check the leds.
Do you have a backlight tester? That could be causing the buzzing as well. Need to know what all voltages from the legend are.

[CapLeaker]

Re: Vizio E400i-B2 missing stand-by voltage

With the psu plugged in, do you get 5VSB on the psu (your 2nd pic, very top left connector)? If not unplug the main board and see if it is there now.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

With the psu plugged in, do you get 5VSB on the psu (your 2nd pic, very top left connector)? If not unplug the main board and see if it is there now.

Thanks for the reply, I have the PSU out of the TV and only plugged in to the wall. There is no stand-by voltage.

[CapLeaker]

Re: Vizio E400i-B2 missing stand-by voltage

Then that psu is bad if it’s plugged in with the main board disconnected. Now follow the trace of the 5vsb from the connector backwards to the diode then over to the hot side of the psu all the way back to the bridge rectifier.
Your picture isn’t sharp enough for me, but I could follow it back past the transformer.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

Then that psu is bad if it's plugged in with the main board disconnected. Now follow the trace of the 5vsb from the connector backwards to the diode then over to the hot side of the psu all the way back to the bridge rectifier.
Your picture isn't sharp enough for me, but I could follow it back past the transformer.

Is this pic better?

[R_J]

Re: Vizio E400i-B2 missing stand-by voltage

This is an always on power supply, when plugged in you should have voltage on J201 (likely around 15~18v) And also voltage (around 30v)on D203 cathode (center pin)
If there is no secondary voltages, the problem is likely on the primary side so post the numbers of the two ic's (8 pin & 16 pin) and even the 6 pin ac_det ic if possible.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

This is an always on power supply, when plugged in you should have voltage on J201 (likely around 15~18v) And also voltage (around 30v)on D203 cathode (center pin)
If there is no secondary voltages, the problem is likely on the primary side so post the numbers of the two ic's (8 pin & 16 pin) and even the 6 pin ac_det ic if possible.

Please see attached image. Enlarge it to see voltages found.

[R_J]

Re: Vizio E400i-B2 missing stand-by voltage

Please see attached image. Enlarge it to see voltages found.

The voltages mean nothing I you don't post what the ic's are
You are using HOT ground for these voltages correct?

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

The voltages mean nothing I you don't post what the ic's are
You are using HOT ground for these voltages correct?

Sorry about that. Is this what you're looking for? The 8 pin is IC102 and the 16 pin is IC101. I don't know why these uploaded upside down, I flipped them the other way before I uploaded them.

EDIT/ADD: Yes using hot ground via - terminal of bridge rectifier

[R_J]

Re: Vizio E400i-B2 missing stand-by voltage

on ic101, pin1 is the VH input voltage, inside the ic is a startup cell that should provide a vcc voltage on pin 10 of around 13v, 2.4v is too low, try replacing C127.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

on ic101, pin1 is the VH input voltage, inside the ic is a startup cell that should provide a vcc voltage on pin 10 of around 13v, 2.4v is too low, try replacing C127.

C127 replaced, problem still exists

[R_J]

Re: Vizio E400i-B2 missing stand-by voltage

Check the components around the ic, like the mosfets, but I suspect the ic itself could be bad.

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

Check the components around the ic, like the mosfets, but I suspect the ic itself could be bad.

I've found no apparent problems with the components surrounding the ic. I checked online and it looks like that ic will have to come from China. I'm always concerned about counterfeit components from the orient. If I did order one it would take more than a month to get it.

So I decided to take a closer look at the PS I got from SJ. It may not work properly, but at least it will power on the TV, albeit only briefly. I think before I order that IC I'm going to look at possibly fixing the SJ PS.

Here are it's symptoms:

When the TV is plugged in to AC power with the Main board detached, the transformer on the PS makes a rhythmic "click click click" noise about 4x a second. As soon as the Main board is plugged in the transformer makes a buzzing noise. As soon as the TV is turned on the buzzing from the transformer intensifies. Shortly after the screen lights up and displays the "V" the transformer makes a high pitch scream, any text upon the screen disappears shortly thereafter in to horizontal lines, the backlights remain on, the buzzing of the transformer becomes less intense and the TV becomes unresponsive. Unplug from AC power, plug it back in and lather rinse repeat.

I detached the LVDS from the Main board and powered on the TV. the only difference seen was no text appears upon the screen. This leads me to believe it isn't a screen fault.

To me it looks like as more load is applied to the PS the problem worsens, leading me to believe the problem is with the PS and not the MB.

I've called it for tonight. I'll report PS voltages some time tomorrow.

Thanks for your help everyone.

[R_J]

Re: Vizio E400i-B2 missing stand-by voltage

being that this is an always on power supply, it operates in different modes depending on the load, So when the tv is off the power supply operates in a pulsed mode to save energy. If you look at the datasheet for the ic it will explain it.
As the load increases the duty cycle will change.

it could be the led driver board or bad led's. Try disconnecting it and see if the tv stays on, or disconnect the led's to the panel and see if the tv stays on.
There are a few other threads on this model

[DXseekerMO]

Re: Vizio E400i-B2 missing stand-by voltage

being that this is an always on power supply, it operates in different modes depending on the load, So when the tv is off the power supply operates in a pulsed mode to save energy. If you look at the datasheet for the ic it will explain it.
As the load increases the duty cycle will change.

it could be the led driver board or bad led's. Try disconnecting it and see if the tv stays on, or disconnect the led's to the panel and see if the tv stays on.
There are a few other threads on this model

Ok so the first thing I did was to detach the LED connector from the inverter board and plug the TV in to AC power. There was still a buzzing sound coming from the transformer on the PS...until I turned the TV on...and then the buzzing went away. The TV stayed on longer but eventually the PS made what I would call a "bomb drop" sound, or a tone that starts off higher in pitch and decreases in pitch over time. As soon as this "Bomb drop" sound started the screen shut off and the TV became unresponsive.

I also detached the inverter from the PS and re-tested with the same results.

Detaching the control harness from the inverter to the MB makes no difference in these symptoms.