(347) 552-2258 [email protected]

820-3330 Quarter Fan Spin

computercaverva

computercaverva

Member
Looking at a board that started out with quarter fan spin, I noticed that there was a glob of smeared thermal paste by U7201, I cleaned that and found that the thermal paste was now bridging most of the pads on one side of the QFN. I removed U7201 with the plan of cleaning the under area and replacing. I found several oxidized pads and 2 that were blown. Now the board gets a green light and then after a while sitting with the magsafe connected or trying to power it on with the power on pads the green lights cuts off.
 
computercaverva

computercaverva

Member
0V on ALL_SYS. The quarter fan spin stopped after cleaning the thermal paste from around U7201 with 99% IPA. Since then there has been no fan spin and attempts to power on the board end with the green light off but PP3V42 is unchanged even though the light turns off.
 
D

dukefawks

Administrator
First thing is to get a stable green light. Try known good magsafe board and check PP3V42, PPBUS, SMC_RESET, ACOK, etc.
 
computercaverva

computercaverva

Member
I’ve tried 2 dc in boards for some reason when the light cuts out both PP3V42 and SMC_BC_ACOK remains steady even when the light cuts off. I will check smc reset and see if it is getting tripped and causing the light to cut off
 
computercaverva

computercaverva

Member
These voltages remain constant whether the light is on or off:
PP3V42:3.408V
SMC_RESET_L: 3.37V
PPBUS: 12.25V
ACOK: 3.255V

Is the ACOK line low enough to cause the light to trigger on / off? The only other thing I am currently looking into is to see if anything by the current sense area is getting hot and failing and then when cooling down working for a short period of time.
 
A

aprendiz

Moderator
computercaverva said:
PPDCIN: 16.3V
PPBUS_G3H: 12.55V
PP3v42_G3H: 3.40v
PP3v3_S5: 3.409v
PP5v_S5: 5.027v

No S0/S3 rails.
Click to expand...


computercaverva said:
These voltages remain constant whether the light is on or off:
PP3V42:3.408V
SMC_RESET_L: 3.37V
PPBUS: 12.25V
ACOK: 3.255V

Is the ACOK line low enough to cause the light to trigger on / off? The only other thing I am currently looking into is to see if anything by the current sense area is getting hot and failing and then when cooling down working for a short period of time.
Click to expand...



So, what is it??
 
You must log in or register to reply here.
Top