Vizio M502i B1 - Missing all power except 5v

[budhanes]

Been working on a few televisions for awhile now, and thanks to everyone who posts. Learning so much! Anyways, working on Vizio M502i B1 power supply board with no voltages on CN9101 except for the 5v at pin 15 and 16. Traced it all down and I have an IC9301 that is a A6069H chip. As per the data sheet, this chip needs 13.8 - 15.3 volts to "start up". I only have 12.8 volts? I have attached a pic that was posted here 9/27/206 by Bud M. It shows the same board I am working on. Any ideas why the required 13.8 - 15.3 volts on my board is only 12.8 volts? This is tested with power supply forced on with a 1k resistor. Thanks!

[handsworth]

Re: Vizio M502i B1 - Missing all power except 5v

First of all, I'm not a technician so that diagram is foreign to me. I've done that Vizio series many times and found that the main board was always at fault. Is your mb good? Bad eprom causes tv not to come on, but ps and backlights are good. Just an idea since I'm 1st to reply

[dick_barton]

Re: Vizio M502i B1 - Missing all power except 5v

What's your power supply board number?

[budhanes]

Re: Vizio M502i B1 - Missing all power except 5v

(X)ADTVD3613XA7 1502
ESP35000X 2943193 A 0353

From the white sticker.

Seems if I let is sit for a day or two and apply power, I will get the 12 volts for a short moment, but goes away. I have tried freezing components with canned air, heating with a blow dryer, etc. Seems not temperature related, but time related??? I discharged all caps and applied power several times to see if it was just the caps draining overnight. Driving me crazy, but gives me a chance to put my new isolation transformer to good use! I know for a fact that in 24 hours when I apply power it will work momentarily yet again.

[R_J]

Re: Vizio M502i B1 - Missing all power except 5v

IC9301 IS the standby ic, so that is not where the problem is. Check the voltage on one of the main filter caps, C9811 or C9812. The voltage in STANDBY, should be around 160vdc, When you force the power supply ON it should go to 385vdc, This tests the pfc circuit. The main ic that develops the +12v & +24v is ic9101
If the voltage on the collector of Q9101 is low, Replace C9305 and maybe C9805 & C9122 as well

[budhanes]

Re: Vizio M502i B1 - Missing all power except 5v

Thanks. When I force the supply on, I do get the 385 vdc. I did replace C9305 when testing the caps previously. I'll text the IC9101 tomorrow and post my results. I did order this ic from "SJ" (not sure if allowed to promote) and should be here Friday. Thanks for the reply.

[R_J]

Re: Vizio M502i B1 - Missing all power except 5v

If the problem is intermittent, I doubt it will be an ic. (we use SJ pictures all the time so it's not a problem that I am aware of) Like I said, if you don't have the pfc boosted voltage, you likely will not have the main ic voltage.
IC9101 should be a LCS703LG-TL

[dick_barton]

Re: Vizio M502i B1 - Missing all power except 5v

Can you post a photo of your power supply board?
RJ do you know the model number of the psu?

[budhanes]

Re: Vizio M502i B1 - Missing all power except 5v

I do have boosted voltage. I was thinking the same thing about it working intermittent, why I suspected the caps, and even tried cooling and heating the board.

This is the board I have. (From internet)

[budhanes]

Re: Vizio M502i B1 - Missing all power except 5v

[dick_barton]

Re: Vizio M502i B1 - Missing all power except 5v

The board number is 715G6100-P04-003

[nomoresonys]

Re: Vizio M502i B1 - Missing all power except 5v

What exactly are all the voltages on CN9102 when you force on the powerboard with the resistor and are they steady? Remember that's with the cable unplugged.

[R_J]

Re: Vizio M502i B1 - Missing all power except 5v

I do have boosted voltage. I was thinking the same thing about it working intermittent, why I suspected the caps, and even tried cooling and heating the board.

This is the board I have. (From internet)

The pfc circuit is working so I suspect the VCC is ok, but check the voltage on Q9101 emitter, it should be about 16vdc.
The power supply does have OVP (Over Voltage Protection) on the +12 & +24 volt supplies, I am starting to think it might be a backlight issue on this tv?

[budhanes]

Re: Vizio M502i B1 - Missing all power except 5v

Well, update, I replaced IC9101 and IC9301 and "popped" R9311 and 9312. The same as this guy did... I double and triple checked chips installed correctly with no solder bridges. Chips from reputable supplier. (SJ)

https://www.badcaps.net/forum/showth...t=r9311&page=4

They appear to be 1R2, or 1.2 ohms.

So now, the backstory on this set, which I am thinking about. A neighbour gave me the set, said one day, a breaker popped in circuit panel, and he reset the breaker, but the tv didn't work anytime after. So, he bought a new tv, and put this in storage. One day, he said, he plugged it on to see if it would work, he got the Vizio logo and it went back off and wouldn't come back on. (I seen the same when testing the supply, The first time after 24 hours of being unplugged, would supply all voltage). So, I am wondering if whatever blew in the tv took out itself and one of the ic's, thus, when I replaced the ic's, I still had a short somewhere and blew R9311 and R9312???

Wonder why the guy in the above mentioned post experiences the same thing???

Just thinking out loud.

[R_J]

Re: Vizio M502i B1 - Missing all power except 5v

Why would you replace ic9301 ? This is the standby ic which WAS working. If you blew R9311 & R9312 you either did something wrong or the ic was bad. (the resistors are 1.2Ω) The resistors are in the source of the internal mosfet, so IT will have shorted (pin 1 to pin 7,8)