U5 got over heated with unstable screen, how to find short?

U5 got over heated with unstable screen, how to find short?

Postby farzadlatifeh » Sat Dec 29, 2018 10:13 pm

I have white screen problem in my DSO138
After detaching LCD I found U5 got overheated
Firstly I removed L3 but overheating happened again
Then I put back L3 and removed jp4 connection and overheating disappeared
Now I know the +3.3V branch has a problem like short
But I don't know what to do for solving it permanently
I tried test mode for possible short on MCU pins but LED was blinking slowly
I checked +3.3V resistance with GND and there was no short, so MCU is OK and there is no internal short
then I checked pin 32, 33 and 34 of LCD header for possible short but it was OK
Then I checked C16, 17, 18, 26 and 15 but they were OK too
Finally I checked pin 5 of CPL, SEN1 and 2 for short with GND but there was no short also there


Any Idea will be appreciated deeply
Thanks
farzadlatifeh
 
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