Vizio M320SR turns off after logo

[Roush2fast]

Hello all , thank you in advance for any input provided.

I have owned this TV for about 2.5 years and never had any problems until last night. My wife was online and the picture just faded out to a black screen. I unplugged the television and did a reset with the power button. Upon reboot the logo flashed as normal and the picture returned. It went out again about 15 seconds after that. The television's behavior kind of fluctuates with sometimes needing to be unplugged to power down to booting with logo and 15 seconds of screen to logo then black. The Vizio light at the bottom of the set stays illuminated when the screen is black. The back light is not on and there is no picture via flashlight test. I have contacted Vizio support and unfortunately I am out of luck. I did ask if there were any firmware updates or eeprom kits available to no avail.

I removed the rear panel and inspected the power and main board. All caps and pcb's appear to be ok visually but when I plugged the set back in I noticed a very high pitch whine coming from the power board. I used a straw and believe I identified the source of the pitch. So, is this a transformer and is it common to have an audible indication of failure? Could this be the source of the problem with the set? I have a basic skill set to solder and replace it as well as perform dmm tests.

Again thanks in advance for any advice or input.

[Roush2fast]

Re: Vizio M320SR turns off after logo

Ok well I was hoping I would have received a response by now but quick update if anyone has any suggestions. I left the TV unplugged for a few days and tried it out today. It seems to be functioning normally but I have not tried leaving it on for any extended period of time. It is still making the high pitch noise that is similar to a ringing in the ear. Is that the switching transformer in the pictures I attached in first post and can it cause the symptoms I listed if malfunctioning ?

Thanks

[dick_barton]

Re: Vizio M320SR turns off after logo

Could you post a sharp picture of the whole of the power supply which may prove helpful.

[Roush2fast]

Re: Vizio M320SR turns off after logo

Well this isn't very sharp so if need be I will have to get a better image for you this evening. Also included the back of the tv.

[dick_barton]

Re: Vizio M320SR turns off after logo

What's the DC voltage across the legs of each of the two long capacitors?

[Roush2fast]

Re: Vizio M320SR turns off after logo

Sorry for the novice questions but do I check with the television powered on , in standby of after powering down and unplugged ? Also do I just apply the leads to each leg of the capacitor or go from positive to chassis ground ?

Also , just noticed the high pitched noise is only present on standby as it stops when the set is powered on.

[dick_barton]

Re: Vizio M320SR turns off after logo

You can check both in standby and then out of standby.

[budm]

Re: Vizio M320SR turns off after logo

Measure between the (+) and (-) legs of the cap.
Chassis GND is not used for Voltage measurement GND ref point in the HOT side of the circuit.

[Roush2fast]

Re: Vizio M320SR turns off after logo

Stand by
Left cap c9801 6v
Right cap c9802 4.9v

Power on
Left cap c9801 172v

Right cap c9802 172v

[Diah]

Re: Vizio M320SR turns off after logo

do you still hear the sound when the screen faded to black ? yes mean backlight issue use torch light on screen with dark room you will see the picture.

[Roush2fast]

Re: Vizio M320SR turns off after logo

No the sound stops when I turn the tv on so even with the screen off the sound was not present. I am on the set now and it seems to be working. The sound still comes back though when the tv is on stand by. I found a power supply board on EBAY for under $30.00. If recommended I will just go ahead and change it out. The component in my first post is the source of the whine. Could this cause the symptoms I listed and just because it's making the pitched nose does that mean it's faulty?

[dick_barton]

Re: Vizio M320SR turns off after logo

What is the voltage written on C9801/2. It looks like your PFC circuit has stopped working.
How confident are you with taking measurements and using a soldering iron?

[Roush2fast]

Re: Vizio M320SR turns off after logo

I will check later but I know the voltage written is 400+ for sure. I am confident as long as you recommend exactly what I need to do in regards to measurements. I get a little nervous around high voltage but I am very careful. As far as soldering that is not a problem.

[dick_barton]

Re: Vizio M320SR turns off after logo

Can you give the numbers written on the IC's but not the 4 pin IC's.
I can see one 8 pin IC on the top of the psu and there will be more on the solder side.

[Roush2fast]

Re: Vizio M320SR turns off after logo

I will do that shortly. Quick update , the tv worked for a few days after being powered down for a while but it is turning off again. I do have sound and I can see a picture with a flashlight. I double checked the capacitor voltage we referenced earlier and it hold steady at 389 when the TV is powered on. The caps are rated 450v.

With this new information where do I go now ?

[Roush2fast]

Re: Vizio M320SR turns off after logo

Can you give the numbers written on the IC's but not the 4 pin IC's.
I can see one 8 pin IC on the top of the psu and there will be more on the solder side.

Having a little trouble determining what you are referring to.

[dick_barton]

Re: Vizio M320SR turns off after logo

The IC of interest is IC9301 which I believe is an STR-A6069H
Can you very carefully measure what dc voltage you have (when you power up) between pins 5 and 3. It should be a minimum of 13.8V
Check all the diodes around the IC


Photo's courtesy Shopjimmy

[Roush2fast]

Re: Vizio M320SR turns off after logo

The IC of interest is IC9301 which I believe is an STR-A6069H
Can you very carefully measure what dc voltage you have (when you power up) between pins 5 and 3. It should be a minimum of 13.8V
Check all the diodes around the IC


Photo's courtesy Shopjimmy

Good call , A6069H SK153 26795D

IC voltage reads 13.7 ~ 13.8 when powered on.

These tests were done when the TV is in a functioning state. It's been unplugged since last failure and it is operating again. I received readings ( meter does not have diode function ) from all diodes excluding ZD9303 and ZD905 which are indicated in the attached picture. Not sure if that means anything as my level of understanding is still elementary. I am learning more and I find this very interesting.

The transformer is still squealing like a stuck pig in stand by.

recap
TV turns off after logo
No back lights
Has sound
Flashlight test revealed image
High pitch noise in stand by that stops when powered on
TV works properly when powered down for 24 hours

Where do you recommend I go from here?

[dskall]

Re: Vizio M320SR turns off after logo

Noise from power supply can mean something is loading it down. I would check diodes and caps around transformer and standby 5v rail. You might want to apply heat to boards when working as it seems to have problems after it warms up

[dick_barton]

Re: Vizio M320SR turns off after logo

Does the large capacitor still have 389V DC when the set is squealing and are all the DC output supplies still operating and is there still 13.7V on the IC A6069H between pin 3 & 5.

If you disconnect the Inverter cable does the squealing stop.