820-2849 dead after gpu replace

[Dozer]

hello group.

after gpu replacment not able to turn on that board.

missing PPCPUVTT_S0

need some help, u7600 replaced already, problem still the same

 

[Dozer]

by heating the CPU the value U7600 pin 4/5 goes down to 6 Ohm.

Is it needfull to reflow the CPU or to reball?

 

[dukefawks]

Remove GPU and see if it works again...

 

[Dozer]

removed GPU now but same results :-(

 

[dukefawks]

I see nothing wrong with the values around U7600. Was this working before you touched the GPU? What is resistance to GND on L7630?

 

[Dozer]

No Title

yes it was working bbefore i touched the gpu. it had problems when heavy working grafical things on the external gpu, internal no problems.

resistance to GND on L7630 is 16.6 Ohm, red on ground in diode mode i get 0.020

i pulled out L7630 now and injecting 1.05V into pin2 of L7630 and in that moment the voltages brakes down (GPU pic1 is sinking down slowly) the lab power supply shows 1.2A and voltage breaks down to 0.7V

PPBUS_G3H is not breaking down

 

[dukefawks]

I have no idea, 16 Ohm is not too low. Signals around U7600 look ok. I have no idea other than you fried it by heating everything too much.

 

[Dozer]

hmmm. I used the same thermo profile like over years without problems.

so do you can explain why the voltages are going to zero by injecting 1.05V ?

can here be a problem with cracks under u1800? PPCPUVTT_S0 is connected with PP1V05_S0_PCH and PPVTT_S0_PCH ?

when injecting the 1.05V into Pin2 L7630 only the S0 and S3 Rails going down to zero,

S5 rails,
PP3V42_G3H,
PPBUS_CPU_IMVP_ISNS and
PPBUS_G3H

not going down to zero.