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820-4924-A no display, no bklight but it has chime

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Dewanbd

Member
  • hi everybody, after long time back to work. This is water damage ,A1502., 820-4924-A Turn on but no image no bklight but chime.

    ppvout-s0=0v
    pp5vr3v3_sw-lcd= 0v
    connector pin 28,29,30= 0v and pin5 =0v
    bklt-en=0v
    smc-lid =3.4v
    scl=.458 and sda=.468 diode mode.
    U8330: PIN1=0V, P2,5=0V,P3=0V,P6=0V,P7=0V,P8=3.3V
    U8340: P4=0V

    now i am stuck, i checked with good known screen same model. no luck.
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
Where was the liquid spill?

"connector pin 28,29,30= 0v and pin5 =0v"
You must get 5V at least in the first seconds, when power on the board.

"Turn on but no image no bklight but chime."
Look if has USB acivity; board could get stuck after chime...
Did you check external video?
 
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Dewanbd

Member
This is water damage everywhere.
at least in the first seconds, when power on the board= 0v
No USB Activity, no external also.
 
2informaticos

2informaticos

Administrator
Staff member
Pufff, you must clean the board and rebuild corroded traces, change affected resistors/capacitors.
You may consider trash it; could be wasting time...
 
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Dewanbd

Member
After 10 minutes ultrasonic and 8 hours dry up, found
video connector pin 3&4= 5.1v, p1=0v, p5=3.3v but after 5 seconds it drop 0 v.
Found water damage around U8300, and pin1=5v, p2=0v, p4= 5v, p6=0v and p7=0v.

Please help me what it could be the problem. Thanks in advance.
 
2informaticos

2informaticos

Administrator
Staff member
"p5=3.3v but after 5 seconds it drop 0 v."
It comes from U8310; this means you have EDP_PANEL_PWR_OR_PSR_EN present in that moment.
This signal comes from U8330!
So check U8300/30/40 voltages in these 5 seconds...
 
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Dewanbd

Member
check U8300/30/40 voltages in these 5 seconds...as following
u8300:
1= 5 then drop 3v , 2= 3.2 v drop 0v , 4=5v stable. ,6= 0v , 7= 0v ,

U8330: P1=0V, P2,5=0V,P3=3.3v & drop 0V, P6=3.3v & drop 0V, P7=0V, P8=3.3V.

U8340: P4=0V, P5=3.3V, P1=0V.
 
2informaticos

2informaticos

Administrator
Staff member
I don't see pins 4 & 6 on U8300; which schematic use you?
Please provide accurate information...

Pins 1 & 4 of U8340 should go high in these 5s; if not panel is not recognized.
Try another compatible LCD assembly.
But need correct readings from U8300 first.
 
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Dewanbd

Member
this was schematics error, the right one is as following:
U8300:

P3=5V
P5=0V

U8340: p1= 0v and p4=0v tried good known lcd.
 
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