00165 no backlight

was liquid damaged around lcd side. sent through ultrasonic clearer. replaced the fpc, backlight ic and filter. powered on and it blew the filter. Where should i start to find out the short? i checked the caps and none seem to be short.
 
Last edited:
okay fuse broke again and it cracked c7799. replaced them both and now have a stable 8.49v going to backlight. is the backlight ic bad again?
 

2informaticos

Administrator
Staff member
Never power up a board before checking for short, or any reason of the burnt component found there!!!

Check traces between U7701 and L/D7701.
Pay atention to FB connection.
Many times gets bad solder under U7701; also XW7720 get corroded (near L7701)...
Post voltages around U7701.
 

2informaticos

Administrator
Staff member
Did you check all continuity mentioned above?
Be sure no broken/corroded trace and check the 6 return resistors too.
PRAM done?
Other LCD assembly tested?
 
No Title

okay found the missing testpoint!

my question is on board view there shows xw7720...but on the board there is no such part! where do i run the wires for this testpoint???????
 

Attachments

  • photo2016.jpg
    photo2016.jpg
    3.4 MB · Views: 1

2informaticos

Administrator
Staff member
Is just a trace bridge, between L7701 and D7701...
Louis has a video about how to recover it, using two test point from the other side to FB pad of U7701.
First clean the area between L/D7701 and see if possible to recover the bridge right there.
 
if its a trace bridge between those two why do i still have continuity between those two points?

spent a couple min looking for that video and couldnt find it. have any idea where it is?
 
Last edited:

2informaticos

Administrator
Staff member
You must check continuity to the other side.
The trace from XW7720 go inside the board.
In fact there is no direct bridge with a hole; part of the trace is wired on internal layer until FB pad.
 
yes but where? there is no test point on the other side that matches with the board view! Im so very confused. Where is XW7720 on the board?

I understand that a trace is missing and needs to be fixed. All im asking for is a little help on where i need to be running the trace since boardview isn't helping!
 

2informaticos

Administrator
Staff member
A5 ball has a bit of pad which can be used for test.
Be sure that pad has no corrosion; sometime doesn't make contact with the A5 ball right there.

"Louis has a video about how to recover it, using two test point from the other side to FB pad of U7701."
Why don't search in the Louis channel?
 
Replaced the u7701 again. Looks like it caused all this heartache. Probably it sent to much voltage and busted the fuse and cracked the cap. Dunno why i had such trouble with this. Backlights are usually pretty easy to fix.
 

2informaticos

Administrator
Staff member
FB solder fail a lot, don't be surprised.
The internal switch of boost converter from U9701 is connected there...
 
Top