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820-2936 quarter fan spin

Gmorb

Gmorb

Member
checked all spi termination reistors and traces all is good even reprogrammed bios with no luck.

board had prior water damage it did at one point keep fan spinning but got no cpu checked the cpu ton resistors for u7400 even replaced u7400 still no luck and board is back to quarter fan spinning.

maybe its bad cpu?

checked the isl side resistors look fine not too sure where to look now.
 
J

jadao

Member
A shorted rail can also do this issue.
Did you check all rails, the one that are cycling with the fan goiing on aan off aad the one that are steady.
 
2informaticos

2informaticos

Administrator
Staff member
Do you get pulses on all big coils, even VCORE?
SYSCLK_CLK25M_SB correct oscillation?
R7402 is OK?
ALL_SYS_PWRGD is pulsing?
 
Gmorb

Gmorb

Member
All coild except the vcore ones pulse. L7520, L7510, L7550 dont pulse. R7402 is fine ALL_SYS_PWRGD pulses

Cant check with an o-scope but i get a straight 0v no pulsing on SYSCLK_CLK25M_SB
 
2informaticos

2informaticos

Administrator
Staff member
PCH requires SYSCLK_CLK25M_SB.
Check around U2800 and Y2805.
Change U2800 if no way to properly check 25MHz.
You can get cheap analog o-scope from Internet adds; you will need it to confirm oscillation many times.
 
Gmorb

Gmorb

Member
Y2805

pin 1 - pulses up to 0.014v
pin 3 - fluctuates from 0.328v to 0.700v

u2800

pin 1 - 3.3v
pin 2 - 3.3v
pin 3 - pulses up to 0.023v
pin 4 - fluctuates 0.647v to 0.743v
pin 5 - pulses 1v
pin 6 - 1v
pin 8 -0.065v and drops to 0.055v
pin 9 - 0v
pin 11 - pulses 1.7v
pin 12 - 0.396v
pin 13 - 3.4v
pin 14 - pulses 2.4v
pin 15 - pulses 0.895v
 
2informaticos

2informaticos

Administrator
Staff member
Change Y2805 and associated caps and resistors.
I have no idea what value should show pin 9 in DC scale; supposedly cannot stay at 0V.
I recommend you to get an o-scope, or frequency meter.
 
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