Vizio E321VL - 2 Seconds to Black

[bobbyskillz]

Hello, friends.

I've been making progress with a Vizio E321VL that was victimized by an apparent power surge. On the PSU it took out the fuse, a SMPS IC (FSQ0465R), and a MOSFET (FQP13N06L). Now I have two seconds to black. After replacing those components, all the power at the cable going to the main board seems proper, except VBR_B drops from 3.3v to 2v gradually after the backlight goes out.

I've poured over other threads here to get some clues, but none appear to have a solution for the same problem. I've tried disconnecting the IR receiver board; it didn't work.

I've been a lurker on these forums for years. I think I read through these posts more than the news these days. Any hints you might be able to give would really be appreciated.

Thanks for looking!

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

The transformers are getting about 2 ohms on the primary and 22 ohms on the secondary. I tested with another set of backlights and had the same issue, two seconds to black. ��

I checked every discrete diode. I swapped out ceramic capacitors I had spares for, including the ballast capacitors. What am I missing?

[CapLeaker]

Re: Vizio E321VL - 2 Seconds to Black

Check out this: https://www.shopjimmy.com/vizio-0500...repair-kit.htm

Maybe this gives you a better idea where to look. On these you have to check certain resistors and even replace IC's.

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

I checked all the through-hole components listed - and most of the listed SMD ones, save some resistors. I even replaced the backlight PWM IC and half bridge resonant converter IC.

I still have the two seconds to black and don't feel like giving up until I fry something. It's a matter of principle now.

Does anyone happen to know what VBR_B stands for? What its purpose is?

Thanks for looking.

[budm]

Re: Vizio E321VL - 2 Seconds to Black

Back lights dimming control signal.

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

Thanks, budm.

I pulled up these two resistors that are both reading .8 ohm. I can't deduce the value based on the color bands. Is it possible I have failed short resistors? That would be a first for me.

[budm]

Re: Vizio E321VL - 2 Seconds to Black

Resistors are fine.
1) We need good clear straight shot pictures of the whole top and the bottom side of the power supply/inverter board. We also need the pictures of the whole backside of the TV showing all the boards.
2) What are the designator for these two parts you replaced: SMPS IC (FSQ0465R), and a MOSFET (FQP13N06L)? IC (or U) 123? Q123?
3) What dc Voltage do you get when measure right between the two legs of the main filter cap (68uF 450VDC) when power switch is activated? around 380 ~ 400VDC?

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

These were replaced:

Q201 13N06L MOSFET
U101 Q0465R SMPS
F101 Fuse
U601 H601G half bridge resonant IC (don't know if it was bad)
U401 oz9977bgn backlight PWM IC (don't know if it was bad)


Filter cap has 172v with the TV off, 158v with the TV and backlight on, and 168v after the backlight goes out.

I took these pictures before I soldered those resistors near the filter cap back. I know my SMA job isn't the best, but it's a new practice for me.

[budm]

Re: Vizio E321VL - 2 Seconds to Black

"Filter cap has 172v with the TV off, 158v with the TV and backlight on, and 168v after the backlight goes out."
If that measurement is correct, that means the PFC Voltage booster is not working, it should have about 380 ~ 400DVC between the two legs of that main filter cap. The inverter circuit needs that boosted Voltage to run correctly.
https://www.badcaps.net/forum/attach...3&d=1542418212
Did you solder those two resistors in that PFC section in place where the main filter cap is?
You also need to check the resistance of that white rectangular fusible resistor next to the filter cap.

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

I soldered the resistors and took the readings after I took that photo. I took the readings twice with the same results using a Craftsman DMM. That white resistor read 1 ohm.

[bobbyskillz]

Re: Vizio E321VL - 2 Seconds to Black

Thanks for putting me in the right direction, budm! I found the problem was a MOSFET (k8a60da). I previously checked the diode function between the source and drain and it was fine. I now found low resistance between the source and gate. I replaced the MOSFET and have good functionality. My lesson has been learned.