820-3476-A chime no image, crazy fan spin

Nick

New member
hi, got a 280-3476-A with no liquid damage and reportedly never dropped. i got chime but no image (not backlight problem) not even on hdmi. after a while of being turned on the fan spins like crazy, i never had this behaviour before so what should i look for?
 

2informaticos

Administrator
Staff member
Confirm to have USB activity; just to assure board is not stuck after chime...

"no image (not backlight problem)"
So you get backlight?
Black, or white screen then?
 

Nick

New member
no backlight problem as no image at all,

caps lock does not go green when pressed, external mouse light comes on
 

2informaticos

Administrator
Staff member
Always better to check USB activity using USB OSX pendrive with link LED; if flashes, 100% board is booting.

Assuming USB activity, post voltages of J8300, pins 9 & 28-30.
 

Nick

New member
pin 9 0.24v without lcd conmected. 0v with lcd connected
pin 28/29/30 5v without lcd connected 1.8v with lcd connected

this with 2 different assemblies



blinking light on external hdd with osx installed
 

2informaticos

Administrator
Staff member
Pins 28-30 should get 5v at least first few seconds (even without LCD), when power on the board.
At same time pin9 should go to 2.5V; 5V will drop if not.
Post voltage at both pins of L8300, with LCD connected...
 

Nick

New member
L8300 1.79 v before and after with the lcd connected
pin9 0 volt with lcd connected
 

2informaticos

Administrator
Staff member
Post now U8300 voltages.
If it gets 5V at pins 1 & 3 and 3V at pin 2, you should get 5V at pin 5 too...
 

2informaticos

Administrator
Staff member
"pin 28/29/30 5v without lcd connected"
Check that again.
Impossible to get 5V output if enable pin is low; unless U8300 is bad.
Better to change U8300...
 

Nick

New member
bypassed it for testing and screen turn on. gonna order one. meanwhile i have to solve the crazy fan spin thing
 

Nick

New member
installed one rom another board temporary and it works. does the fan go crazy if no trackpad is connected? because his own is extremely water damaged
 
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