Green light, not turning on. missing voltage rails
Hi
I have started working on an old obsoleted board again.
It is the A1229 model
This machine does not auto power on so I plugged in charger and touched the power on pads with tweezers and got green light
The fan spins and stops, It keep on doing this
I get 5v on pin 1 on u7300, which is PP5V_S5
I have 4.9v on PP5V_S5, I checked on c8900 to confirm
I checked all_sys_pwrgd, on Pin 4 of u7880 and get 3.2v
On c1252 which is PPVCORE_S0_CPU i get 0,7v
If I keep My probe on c1252 and when the fan starts I get 0.7v but then when fan stops the voltage goes down to 0v but when fan starts spinning again the voltage goes to 0.7v
This just loops
I then started testing resistors surrounding u7900 (ISL6255AHRZ)
I have checked R7905 which is 18.1 ohm
R7906 is 2.4 ohms
R7904 is 000.2 ohms
I cant see anything wrong visually
Update (09/24/2020)
the board is 820-2132-a
Esta pergunta é pertinente?
Hi
can anyone help me please
that is knowledgeable in board repair
Thanks so much in advance
por Mr Fz