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-   -   Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's (https://www.badcaps.net/forum/showthread.php?t=68099)

triplefour 03-07-2018 09:44 PM

Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
3 Attachment(s)
All voltages on the PSU seem fine. i have 12v and 24v going to the Driver board and Mainboard. strangely this PSU does not have a wire where the 5V should be. also theres some other unused pins that are labeled for 3D stuff.
never worked on a tv where the PSU didnt have 5v...

the tv responds to the power button, increasing the PFC from 170 or so to 400 and staying there, plus all output voltages seem fine and stable. another press of the power button followed by a long press will result in the tv shutting off (as these models with only one button do)

on the driver board CN806, is the cable coming from the PSU, and it reads 24v for pins 1-4 and 0v for pins 5-8
also on the driver board, CN805 is the cable coming from the Mainboard and reads as follows:
1-0
2-0
3-3.03
4-0
5-0
6-0
7-0
8-4.87
9-0.03
10-12
11-NC

of course i have no idea what the voltages should be on this connector...
because none are marked, on the top or the bottom, or on the mb.
and also there are no voltage markings for the cables that go to the LED's

but at the end of the day, i have 0v on all pins of all 4 connectors that go to the LED's

because PSU seems to be outputting correct voltage, and MB is responding to pwr button to turn on and off, i lean towards the problem being with this driver board.

only thing has me worried is i think i should be able to see image with a bright flashlight but i cannot.
i would like to test for sound but its hard to change the inputs blind...

i find a lot of LED driver boards on ebay for pretty cheap, but i'd like to be a little more sure before just throwing parts at it.



thanks for any input!

budm 03-07-2018 10:00 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
So you have 24V feedin the LED driver board when you turn on the TV, correct?
The LED driver board has 4 converter circuits (4 inductors L801 ~ L804 for circuits) but not 100% sure yet because the caps are only rated at 35V so they may not be boost converter but may be buck converter. One way to tell is to get the P/N of IC 601 ~604 to see what they are.
Based on this picture: https://www.badcaps.net/forum/attach...1&d=1520484273
What DC V do you get on the right side pin of those 4 inductors when TV is turned on? they should have at least 24VDC when the boost converters are not turned on by the BL-ON signal.

triplefour 03-07-2018 10:22 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
thanks for the reply. i checked those 4 inductors L801 ~ L804 and found 0v on either side of them.
i have 24v at the connector

triplefour 03-07-2018 10:33 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
2 Attachment(s)
i think you meant IC 801 ~ 804
heres a pic
markings are as i can tell:
Z1269012
ZA4S16

triplefour 03-08-2018 12:56 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
..and i cant seem to find a datasheet for it

budm 03-08-2018 09:17 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
Quote:

Originally Posted by triplefour (Post 810477)
i think you meant IC 801 ~ 804
heres a pic
markings are as i can tell:
Z1269012
ZA4S16

You are correct, they are 801 ~ 804.

budm 03-08-2018 09:24 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
1 Attachment(s)
The IC is made by Alpha & Omega semiconductor: http://www.aosmd.com/
AOZ1269QI-02 Buck converter.
See spec sheet so you start checking Voltages.

triplefour 03-08-2018 11:55 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
could you tell me how you found this datasheet? i was unable...

budm 03-08-2018 01:35 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
I use 'Z1269QI2' as shown in your picture.
You wrote it down as 01.

triplefour 03-08-2018 03:28 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
wow, good eye. i never would have seen that as a Q ....i do see that it wasnt a 1 though, i need to take more time and look more carefully next time. thank you

budm 03-08-2018 03:33 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
You can see how '1' is printed on the first line and on the second line compared to 'I' in the first line.

triplefour 03-09-2018 12:07 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
yes i totally get that but seeing that as a Q instead of a 0 or a O .... that takes skill :)

triplefour 03-09-2018 01:59 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
2 Attachment(s)
ok so i checked those IC's and the pins are really close together so i couldnt get some of the ones that were in the middle, but TON pin reads 9.6v and all the ones i could safely get a read on are 0v.
heres a picture. anything with no voltage written is 0, and the pins on the ic are unknown/0

i get the same readings for all 4 sections

triplefour 03-09-2018 08:31 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
any thoughts?

Kg74 03-11-2018 12:17 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
Follow the trace and take your measurements from that point.

al1415 03-12-2018 08:37 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
Is their a service manual for this TV? P502ui-B1E

triplefour 03-12-2018 09:55 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
i havent been able to find it. i would really like to know what the expected voltages are on the connector going to/coming from the mainboard to the LED driver, so i could tell if the problem is in the driver board or further up...in the mainboard

there needs to be a project where everyone who has a tv, even though it isnt broken, could take a look at what the voltage should be and give us this precious info


i did find this on youtube: https://www.youtube.com/watch?v=PJxlACogZQA
its for a very similar tv (just missing the E at the end)
and its from shopjimmy. they say its a common problem with this tv if you have no backlight, to change the eeprom at u202....but they dont even mention doing the flashlight test to make sure you have picture, or what it would mean if you did or not have picture...

i hate just buying stuff on a guess though, even an educated one. i'd like there to be some definitive test that shows the eeprom is bad before i bother replacing it


edit: i found a place claiming to have the service manual but they want 13$ for it :(
http://www.service-manual.net/ashop/...=catalogue.php

budm 03-12-2018 10:23 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
So pin 2 (EN) is staying low on all 4 IC's?
If it is then you need to trace to see where pin 2 goes to next, so far it looks like pin 2 of each IC is connected to 220 resistor, so I expect the other end of each one of those resistor will be tied together and then goes to one of the connector pin.

triplefour 03-12-2018 11:55 PM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
1 Attachment(s)
yes, i cant exactly probe the pin itself, but the very next thing the trace from EN goes to: R8207 reads 0 on both sides
and so does the thing it appears to be connected to (i have a hard time following these things... do i have to flip the board over? shine with a light? use a magnifying glass... probably)
but anyway it seems like it goes to
C8066
which is also 0 on both ends.
as for seeing all 4 of these sections tied together and going to one connector pin, i have not looked closely enough (i guess), and also which connector? the one from the psu where i have 24v or the one from the mb where i have a few v+ as well?

what did you mean about the 220 resistor? i cant see that anywhere

budm 03-13-2018 09:30 AM

Re: Vizio P502UI-B1E has no backlight, no voltage from driver board to LED's
 
From the pictures I can see the resistor that is connected to pin 2 has '220' printed on top.
Tracing the connection on the board is part of the troubleshooting that needs to be done and it can be time consuming. But at this point if there is no EN HIGH signal to turn on the circuit thane there will be no Voltage for the LED strings.


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