[Fixed] Visio E191VA LED TV - Page 1
Forum section: electronics / repair

author: mbless
author_rank: Regular Contributor
timestamp: April 26, 2018, 02:38:23 pm
content: I’ll preface this post by saying that fixing the TV is not worth the time, but I’m attempting it as a favor for a friend since the TV fits their specific need.The symptoms are no backlight and no visible picture using a flashlight. The TV also is not recognized by a computer. When the power cord is plugged in the light on the front lights up for a second and then turns off. Pressing the power button turns the light on, but the light does not turn off with additional power button presses.Per usual I started with the power supply. Inspection did not reveal any apparent issues, no bulging capacitors, etc. The connector to the main board has some labels as seen in the attached "connector" picture. The table below shows the measured voltages with and without the main board connected and after the power button is pressed. Without a schematic the voltages seem ok. Feedback voltage (I think) from the main board appears on Pin 10 after the power button is pressed. There is barely any difference on the dim and on/off pins, though.PinDisconnectedConnectedConnected & power button10V25mV50mV20V46mV91mV30V0V0V40V0V0V50V0V0V60V0V0V70V0V0V815.4V17.9V18.0V915.4V17.9V18.0V100V80mV5.1V115.4V5.1V5.1V125.4V5.1V5.1V13NCNCNCSearching for fixes online yields very few results. According toShopJimmythe EEPROM is a common failure. This is the specificmain board. The kit appears to include the EEPROM and 3 other chips. It appeared there could be multiple main board issues, so we ordered areplacement from fleabay.Obviously the replacement main board did not fix the problem otherwise this post wouldn’t exist. Still no backlight, no picture, TV not recognized by a computer. The light on the front lights up when the power cord is plugged in and stays lit. Pressing any of the buttons has no effect. Remeasuring the power supply main board connector yields the same voltages. I still don’t measure anything on the pins labeled DIM and O/F; I’m not going to probe it with my oscope if it is PWM since I don’t have an isolation transformer.PinDisconnectedConnectedConnected & power button10V47mV47mV20V89mV89mV30V0V0V40V0V0V50V0V0V60V0V0V70V0V0V815.4V17.9V17.9V915.4V17.9V17.9V100V5.1V5.1V115.4V5.1V5.1V125.4V5.1V5.1V13NCNCNCAs far as a T-con board, it is either built into the main board or goes under the black cover at the top of the TV; I don’t know enough about TVs to be sure. I was about to peel back the cover when I decided to measure the connector. The three red wires are power as it connected to the electrolytic cap to the right. The replacement main board measure 0V, so no power going to the logic. The original main board has 5V there.At this point I am seeking suggestions/thoughts before I return the replacement main board. The main board was claimed to be refurbished but working, but it seems that the original main board has more signs of life (responds to power button, 5V to logic). Does anyone have an idea of what else to check or what normally is wrong in this situation? Thanks for any help!

author: mbless
author_rank: Regular Contributor
timestamp: April 26, 2018, 02:39:07 pm
content: Here are the other pictures that were too large to attach to the first post.

author: grifftech
author_rank: Frequent Contributor
timestamp: April 27, 2018, 02:35:42 pm
content: An image of the back of the psu would help

author: mbless
author_rank: Regular Contributor
timestamp: April 27, 2018, 11:01:42 pm
content: Indeed it would. It's attached now. I didn't find any cold solder joints unfortunately.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 28, 2018, 04:22:18 am
content: are the power supply borad giving the roght voltages, the ground is pin 5 -6 -7 youre supposed to have an constant voltage at the output when the tv is off, i think its the 5.2 voltsVizio had bad capacitors problems in the psu has other brands too ...

author: mbless
author_rank: Regular Contributor
timestamp: April 30, 2018, 01:24:51 pm
content: Quote from: coromonadalix on April 28, 2018, 04:22:18 amThanks for the reply. My first post is confirming the voltages are there.As for an update, I went through the power supply in more detail. I found the data sheet for the PWM boost controller that drives the LED backlight. The main board activates the boost controller with the on/off and dim pins on the main board connector (1&2). I applied 5V to on/off and 1V to dim and the backlights turned on. So I at least know the backlights and PSU backlight circuitry is good.I then hooked up the original main board with the manually controlled backlight, and I can see the TV cycling through colors: red, green, blue, RGB striped pattern, gray and finally black. So it appears to me that the PSU and T-con boards are good.Pressing the power button turns on the white power LED on the front of the TV, but the TV still cycles through the colors. From what I read online, the color cycling is service mode, which you can exit by some button combination. Unfortunately the TV doesn't respond to any button presses except for turning the power on. I even programmed my Logitech universal remote (I don't have the original remote), and again the TV only responds to power on.In short, I think the main board is still at fault. Manually controlling the backlight with the replacement main board yields no color cycling since no power is sent to the T-con (see 1st post).

author: clucas
author_rank: Contributor
timestamp: April 30, 2018, 11:39:16 pm
content: Just curious why you don't buy the kit and repair your own main board. It sounds like a main board issue but could be the common problem with the BGA chip as well. Also what was the refurbishment the ebay seller did? I grilled a seller once for the same thing and he admitted he had just blown the dust off the board.

author: mbless
author_rank: Regular Contributor
timestamp: May 01, 2018, 12:25:00 am
content: Well the kit isn't expected to be in stock ever again. I could buy the EEPROM and see if it fixes it, but for $5 more I can replace the whole board just in case there are other issues like the BGA.The seller didn't refurbish anything, they just pulled the boards from TVs with cracked screens. I spoke with them today, and they claim to test the boards in a working TV.... Anyways they are sending me another one, so crossing my fingers.

author: mbless
author_rank: Regular Contributor
timestamp: May 04, 2018, 01:20:11 pm
content: Update:The TV is now fixed. The 2nd replacement main board did the trick. Based on the few fixes I've seen, I'm guessing it was the EEPROM as they used the cheap Winbond chips.