Vizio E470i-A0 - FL test ok, half bl working

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

BTW I can light both Strings with Shop Jimmy tester at the plug to the board (Disconected) 76.1 vdc and 76.3 vdc

[budm]

Re: Vizio E470i-A0 - FL test ok, half bl working

105v LED 1
Retrun .7VDC
103 LED 2
Reurn Sometimes .7 vdc sometimes 6 v not sure why not sensative to touch also has no bearing on wether the channel shuts down or not
I have on occasion got it to stay up if the tv gets by the first 10 secs of start up iy will stay on for hours but turn the tv off and back on and drops again will drop with in 10 secs if its going to drop I have swapped the leds from ch 1 to ch 2 but ch2 always shuts down no matter what it hooked to it and eve if NO LEDS hooked to it it will shutdown while ch1 will stay up even with no leds hooked to it

Are you testing right at the pin of the LED connector?
LED 1 (CN301 pin 1) is the Cathode return line of LED string #1
Vout 1 (CN301 pin 3) is the boosted Voltage of the LED power supply #1 which is fed to the Anode of the LED string.
LED 2 (CN301 pin 5) is the Cathode return line of LED string #2
Vout 2 (CN301 pin 7) is the boosted Voltage of the LED power supply #1 which is fed to the Anode of the LED string.
So what you are reporting does not make sense to me. All the measurement are ref to chassis GND.
And BTW, you keep referring to CH1 and CH2, where are the test points for CH1 & 2?
is this the EXACT board you have? See post #5.
https://www.badcaps.net/forum/attach...4&d=1491364065
What is the P/N of the LED driver IC 9101? We need to look up the spec sheet of the IC.

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

Are you testing right at the pin of the LED connector?
YES at the board
LED 1 (CN301 pin 1) is the Cathode return line of LED string #1
Yes
Vout 1 (CN301 pin 3) is the boosted Voltage of the LED power supply #1 which is fed to the Anode of the LED string.
LED 2 (CN301 pin 5) is the Cathode return line of LED string #2
Vout 2 (CN301 pin 7) is the boosted Voltage of the LED power supply #1 which is fed to the Anode of the LED string.
So what you are reporting does not make sense to me. All the measurement are ref to chassis GND.
YES
And BTW, you keep referring to CH1 and CH2, where are the test points for CH1 & 2? Channel 1 is the working channel on the outside area of the board D9202 D9202A
CH 2 is D9102 D9102A
is this the EXACT board you have? See post #5.

YES
THe only thing IM sure about is the problem IS on this board

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

SEM5028 IC I( have this on the way from Shopjimmy in some sort of repair kit I have 2 of these boards acting exactly the same ... 1 from ShopJimmy that I will return when I figure this mess out ...

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

Regarding this IC could not find a spec sheet for it only the 5027 which is a single channel driver ... 5028 is Dual Channel

[budm]

Re: Vizio E470i-A0 - FL test ok, half bl working

1) If you look at the pin out of the 5027, you will see OVP (Over Voltage protection) which will shutdown the Boost converter when the Output has no load connected sothe output will drop down from over 100V to 60V (Input Voltage the boost converter). So the 5028 may have Two OVP circuit for each LED driver.
2) How many LED's are there in the set? Base on your reading on your LED tester, 76.1 vdc and 76.3 vdc, since the drive the current is about 30mA fronm the tester, so the Vf of each LED at 30mA will be about 2.7 ~2.9V, so that will be about 28 LED's. When the LEDs are driven at full current, the Vf will be about 3V, so the power supply has to put out about 28 x 3 =84V + 20V for the PWM controlled MOSFET and the current sensing resistors. You indicated that you do have over 100V feeding the LED strings but you had only about 0.7V on the return pins which does not make sense to me unless you still have open circuit.
http://4.bp.blogspot.com/-80jXWtC6Hj...D%2BDRIVER.jpg

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

not open thats the channel thats lit .7 in ref to ground
and this supply does stay up with no leds I tend to look at this like a stereo amplifier and I use the working channel to troubleshoot the bad one...
The pulsing is the doubler shutting down without load and resarting over and over
the BAD channel does this too except only like 3 times then it quits .. the good channel will pulse forever without a load... it never stops trying A spec sheet on that IC will help becuase without it I dont know what Im looking at on this IC

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

there are 6 strings of 9 leds
3 strings on each supply circuit

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

I would tend to think the leds are turned on hard to ground with the .7 reading ...
dont they vary the return to achieve lowering the drive to the leds by switching transistors to gnd ? .. if i have resistance to gnd on that return side wont you see a higher voltage here ? and a dimmer led? I switched some parts from 1 channel to the other as I will do when im working on a stereo amp becuase I move the problem from one ch to the other than I know I found the part ... I swapped diodes caps and current resistors ... nothing changed

[budm]

Re: Vizio E470i-A0 - FL test ok, half bl working

If you truly has on 0.7V (V drops on the MOSFET and the current sensing resistor) on the Cathode return, the LED would have been flashed real bright then the circuit will shutdown due to over current condition, the 0.7V reading is more likely to be open circuit in the LED string some where. Typical Vdrops on the PWM Control MOSFET is 10 ~ 20V typical.
One thing to watch out too is that the tester only puts out 30mA while the drive current of the LED power supply is about 200 ~ 400mA range, so bad LED will breakdown at higher current so the tester cannot simulate that condition.
Something is not making any sense to me right now based on your reported readings.
So the bottom line is that one of the string does not even flash on once, correct?

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

like I said I have the screen off all the leds light just fine one set of 3 wont stay lit ... when you first turn on the tv they all light at full strength then they all dim down as it seeks signal then they come back up not quite as bright as initial turn on this is all normal the tv plays for about 10 secs and one set of 3 strings (powered by ch 2 ) of leds will shut down leaving 3 strings of leds lit up (Channel 1) it doesnt flash they light up solid and I switched the leds for the 3 that quit and made no difference no matter what set of leds If they are powered by Ch 2 they shut down

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

I Have also measured the volatges as it goes through the strings as its some thing like this 105V enters first string 74 V leaves enters second string 38 volts feeds the 3 string as it leaves the 2cd string and by the time you get through the 3rd string you have .7 out the other end all 3 strings lit solid

STEADY VOLTS
So 105v >>>>>>>27 LEDS .7 VDC ,,,,,,,back to power board

thats from the set that works with no issues

the other set is about the same but the starting voltage is lower 103v then as the set plays you can watch that 103 drop 102 still lit 101 still lit 100 still lit.....99v OUT then falls fast to 66 V ...

[budm]

Re: Vizio E470i-A0 - FL test ok, half bl working

'STEADY VOLTS
So 105v >>>>>>>27 LEDS .7 VDC ,,,,,,,back to power board
thats from the set that works with no issues'
27 LEDs x 3Vf = 81V, but you have 105V feeding the Anode and 0.7V on the Cathode return, so V drops on the string is 105V - 0.7V = 104.3V but 27 LED's with total Vf of 81V so where does the extra Voltage drops of 104.3V - 81V = 23.30V go to.
Not only that we are taking about the total Vdrops on the PWM Controlled MOSFET and current sensing resistor (Q9105 + R9110 (0.15 Ohms) for string #1, Q9215 +R9210 (0.15 Ohms)) for string #2) of only 0.70V.
As you can see it does not add up, and you get the same result with replacement power supply.
But you indicated that you have working TV for comparison so if you transfer the board from non-working to the working TV one at a time then you can see if the boards from the bad set are good or not.

[budm]

Re: Vizio E470i-A0 - FL test ok, half bl working

BTW, looking at the color of R9110, 9210 again; they look to be 0.50 Ohms 1%(Green/Black/Silver/ Brown).

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

Ts gets even starnger

CH 2 is affected b the incoming sgnal CH 1 is NOT!
The crazy readings I was getting on the return of CH2 is due to the incoming signal now I know newer tvs varry that with signal to different leds never saw a simple 2 channel supply do it and why not both supplys being affected equally?
this would mean the backlights in edge lower and top vary with signal but the leds in the center dont?
Im going to see if the menu setting is affecting both channels

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

all kinds of vdeo uploading .. SInce the leds were staying on I installed the screen this morning

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

https://www.youtube.com/watch?v=fRnvOHwYq5w
Aparently I am Crazy! ARGH!!!

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

https://www.youtube.com/watch?v=t7solMfM0HM

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

https://www.youtube.com/watch?v=ugTW0UlTG1M

[anthonystv]

Re: Vizio E470i-A0 - FL test ok, half bl working

Are you going as crazy as I am ?
https://www.youtube.com/watch?v=LP71svARSuI