820-3437 Rabbit hole

XooP

New member
First off, completely dead board (another thread).
Got the board starting but fan spins constantly with no light on USB mouse.
No CPU VCORE and PP1V05_S0 at 0.2V.
Found a short on U7400 and replaced it. Now i have PP1V05_S0 But still no CPU VCORE

Found that All_Sys_PWRGD was missing so I replaced U1950 and I have now got 3,8V there.

Still no CPU VCORE, Pin 20 and 22 on U7200 gives me nothing.

Should I just replace U7200 or look elsewhere?
 
Last edited:

XooP

New member
An update, the missing CPU VCORE seems to be my fault, poor U6100 soldering, have now got 1V on pin 20 and 22 on U7200 and I have got CPU VCORE.
Fan still spins constantly and no light on USB mouse.
 

XooP

New member
My god, now all_sys_pwrgd is missing again. It seems like I jumped to a conclusion a little to fast. It seems like CPU VCORE and ALL_SYS_PWRGD comes and goes.
Anyone got any ideas?
 

larossmann

Administrator
Staff member
ALL_SYS_PWRGD is going to come from PP1V5_S0 PP3V3_S0 PP5V_S0 working. If they are all present then look carefully for corrosion in the Q8150 area. This board and the measurements you're giving sound like a ping pong ball you're holding down in water with one finger though so I don't have high hopes here.
 

XooP

New member
No it is not power cycling, when I do get CPU VCORE and ALL_SYS_PWRGD they stay high but I get no boot, only fan spin. I have replaced U1950 and tried with another U6100. All resistors look good but maybe a bad capacitor or something. I'll check Q8150.
 

XooP

New member
I have already put back the original U6100 since it didn't make any difference, I guess I'll try an SMC reflow first and then replace or re-ball.
 
Top