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A1502 2013 13? MacBook Pro Fan Spin, no chine or Display output

Melvinzill

Melvinzill

Member
Have this A1502 here which is missing its display and I sadly have no test displays. So I attempted to power it up and the fan spins but it doesn?t chime or output a signal to an external display. Anyone got a clue what could be going wrong?
 
2informaticos

2informaticos

Administrator
Staff member
Is that 820-3476 board?
Any history available?
Did you try PRAM reset?

CPU VCORE is present?
Also check PLT_RESET_L.

Try known good working BIOS.
Check first all SPI Bus Series Termination resistors and traces.
 
Melvinzill

Melvinzill

Member
Oof completely forget the board number. Me idiot! It?s the 820-3536A board. I have no history on this one. When I pulled the board out I did notice a prior repair though which always sucks. They ran a jumper from L1295 to C1297 as well as replaced C7371. I did try the normal resets without success. VCORE is 2.1V measured on C1031. PLT_RESET_L is 0V. Don?t have a way to flash a new bios to the board atm. What sort of programmer would I need?
 
2informaticos

2informaticos

Administrator
Staff member
No BIOS activity prior PLT_RESET_L, so don't touch it yet.

"VCORE is 2.1V measured on C1031"
Are you really sure?
Too high, check it with different voltmeter.
Also check CPU_VR_READY level.
 
2informaticos

2informaticos

Administrator
Staff member
Change the battery of the other multimeter.
And do not spend lot of money on precision meters; not a real help!

Check for corrosion at U1950; post its voltages.
 
Melvinzill

Melvinzill

Member
Yup the battery did the trick! Now the values match my old meter. Voltages at U1950 are:

Pin 1 - 3.3V
Pin 2 - 1.7V
Pin 3 - 0V
Pin 4 - GND
Pin 5 - 0V
Pin 6 - 0V
Pin 8 - 3.4V

hope those help
 
2informaticos

2informaticos

Administrator
Staff member
You've missed pin 7.
However not important, as pin 2 is not correctly defined.

Check R1950; if good, change U1950.
 
Melvinzill

Melvinzill

Member
Back to this old thread after over a month. Got a replacement U1950 in, made no difference. Also tested the original one on a known booting board and it worked. Any other ideas on what I can try?
 
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