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820-332-a PPVCORE_S0_GFX_REG short to ground

A

appleonarim

Member
Hi
Board is not turning power on when i measure PPBUS_G3H shows 1.5V. Removed F7040-F7041 PPBUS_G3H is 12.5V ok. After injected 3.5v PPBUS_G3H line GPU is warming up. Then I removed R8998,R8999,C8961,C8962,C8963,C8964 GPU is not warming so GPU is dead ? And now also machine can not power on is it normal ( not fan spin and another thing about working) ?
if GPU is not get power machine cant turn on?
 
A

aprendiz

Moderator
Shorted Q8930-Q8931, if Q8930 is shorted (highly possible), you have injected 3.5V directly to GPU, so, maybe, GPU is fried..

If you want to try, replace both mosfets and U8900 and pray for it to work..... :)
 
A

appleonarim

Member
Thanks for help aprendiz but I didnt inject PPVCORE_S0_GFX_REG voltage, injected PPBUS_G3H line 3.5V . And when i removed r8999 and r8998 short to ground stay another side (at PPVCORE_S0_GFX_REG line) so if q8930 and 8931 was shorted groun when i removed this resistors it have to stay short to ground is it correct or i know some things wrong?
 
A

aprendiz

Moderator
Agree with you, but if Q8930 was not shorted or stuck (active or closed), there is no way that GPU gets hot if you inject voltage on PPBUS G3H...

What is the resistance to GND on PPVCORE_S0_GFX_REG??
 
Crizz

Crizz

Member
Remember CPUs and GPUs have a very low resistance so you will get a very low voltage drop in diode mode!
Don't think it is a short to ground! Best way here is to compare values with a working board
 
A

appleonarim

Member
When i check resistance to ground 32ohm shows this board but i have another same board ( not sure about healty) 27ohm shows. ( Also removed R8998,R8999,C8961,C8962,C8963,C8964) red probe at gnd.
 
A

aprendiz

Moderator
Well, there is no short here, just low resistance and thats ok....... As i told you before, replace Q8030-Q8031 and U8900. I hope that GPU is not fried........
 
A

appleonarim

Member
Thanks Aprendiz when i replaced Q8030,q8031 and U8900 same time machine start to fan spin not mounted computer body and didnt connect any cable. After mount computer and connected lcd cable and other cables it stoped again :( same problem at start. 0,25 A use at powersupplay connect and nvidia litte hot, not fan spin and ppbus_g3h line is 1.5v . is this problem cause by damaged LCD? or nvidia try to turn on when lcd connected its damage q8030,8031?

Note: when i change only q8030,q8031 at same time not working when i change q8030,q8031 and u8900 same time,fan spins but connected LCD totaly dead and same parts damaged:(

any body have idea?
 
A

aprendiz

Moderator
Replace all parts again and test by thunderbolt before connect the display, see if you have video, also check display connector and cable...........
 
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