A1311 late 2009 820-2494A only 1 led non starting

[ex250]

Hello, unsolded from a donor a D7301, values where different on diode, so changed it first

Results:

P1->3,36
P2->4,55
P3->1,078
P4->0,801
P5->5,09
P6->5,09
P7->5,09
P8->GND
P9->2,89
P10->5,09
P11->12,08
P12->9,98
P13->7,09
P14->5,09
P15->5,09
P16->1,25

But still not working led 2 of the board.

 

[2informaticos]

Check voltage on other big coils.

 

[ex250]

L7320->5,08
L7460->0,01*
L7610->1,21
L7660->3,37
L7920->1,11

Seems that there is a problem at the L7460, likely u7401 related? what to check there?

Many thanks for all your help and guidance

 

[2informaticos]

Check U7401 voltage; pins 14, 16, 22, 29.

 

[ex250]

U7401
14 -> 12,08
16 -> 5,09
22 -> 5,07
29 -> 3,33

 

[2informaticos]

Seems to have similar problem.
Check resistance to ground at L7460 (ohm scale).

 

[ex250]

L7460 to ground-> 5,5 Ohms

 

[2informaticos]

Value looks good.
Check U7401 surrounding components.
If all good, change the chip.

BTW, any reason to quote an entire post, visible few centimeters above?
Write directly into reply box, instead of clicking Reply button...

 

[ex250]

Just only find a too high diode value at pin 13 of the U7401, 2,056

 

[ex250]

Just replaced the U7401, now the second light powers up, mounted the system, but powers, fan speeds up and power down again. No post error sounds, no "dong" sound and no screen powering up.

 

[2informaticos]

L7201/21/41 voltage appears?
Check ALL_SYS_PWRGD and PCIE_RESET_L, when fans spin.
You may need to test with other MXM graphics card.

 

[ex250]

L7201/21/41 0,01v
ALL_SYS_PWRGD 3.38v
PCIE_RESET_L 0v


The MXM card is a working one.

 

[2informaticos]

Check voltage at pins 19 & 32 of U7100.

 

[ex250]

P19-> 5,056v
P32-> 1,085v

 

[2informaticos]

Check pin 33 too...

 

[ex250]

P33-> 3,37v

P36->0,05v

 

[2informaticos]

Try changing U7100.

Did you test with known good CPU?

 

[ex250]

Tested with a functional CPU, still same. I started the board without CPU and there is 1.28v at the L7201/21/41

Seems that something shorts them with the CPU inside... Could inject that voltage to find any heating element, if there is any other, apart the cpu.

What do you think?