A1398 820-3071-A with no image

[hgoncalves]

Hi, after remove the L8930 the short seems to be gone (3 M ohm on PPBUS_G3H ), but the coil seems to be ok (at least it has continuity).
I have another board for parts, but it doesn't have the L8930/60 coils.

Can you tell me on witch boards can i get an 0.2UH-20%-24A-0.003OHM coil,or if i can use other from that board with a different value?

 

[2informaticos]

The coils are good, more than sure.
Replace high-side MOSFETs from GPU power supply (Q8930).
After that, post resistance to ground at L8930/60 and PPBUS_G3H; before applying power.

 

[hgoncalves]

Ater resoldering the L8390 and replacing Q8930 i get:

L8930 = 0.40 ohm
L8930 = 0.40 ohm
PPBUS_G3H = 2 M ohm

 

[2informaticos]

0.4 ohm is pure short.
Lift L8930/60 and check which side the short remains...

 

[hgoncalves]

the short is on PPVCORE_S0_GFX_PH2. Shell i remove R8998?

 

[2informaticos]

You can inject 1V there and check if GPU gets hot.
Remove heatsink first.

Let amp to max on PSU.
You may need 20A PSU for test...

 

[hgoncalves]

I don't have a 20 A PSU, but even with one of 5A, it only consumes 0.555 A. and don't gets hot. On thermal cam, i can't see anything hot

 

[2informaticos]

Go bit up, until 1.2V no more.
Check directly on GPU die.

 

[hgoncalves]

With 1.2V it only consumes 0.655Amp, and still nothing hot. What do you mean with "Check directly on GPU die"?

 

[hgoncalves]

Something change, and i can't figure out why;

now i have

L8930
PIN 1 = 23 k ohm
PIN 2 = 21.80 ohm

L8960
PIN 1 = 0.40 ohm
PIN 2 = 21.80 ohm

Both coils out

 

[2informaticos]

Looks better now.
Resolder coils and check again the value.

 

[hgoncalves]

hi,

After resolderind both coils, all shorted again. All mesures in both coils arround 0.50 ohm.
L8960 seams to be a little damaged. Where can a take a similar coil on this board?

 

[2informaticos]

These coils have no pin connected to ground!
How then a coil can pulls down to ground???

Lift the coils again and check resistance to ground on each pad.

BTW, did you apply power to the board???

 

[hgoncalves]

No, no power. I'll lift them again to measure them.

 

[hgoncalves]

Both coils out:

L8930
PIN 1 = 26.26 k ohm
PIN 2 = 26.80 ohm

L8960
PIN 1 = 0.40 ohm
PIN 2 = 26.70 ohm

 

[2informaticos]

Change Q8961 and check again.

 

[hgoncalves]

After replacing Q8961 i get those:

Both coils out:

L8930
PIN 1 = 26 k ohm
PIN 2 = 27.00 ohm

L8960
PIN 1 = 25.90.K ohm
PIN 2 = 27.20 ohm

Aren't pads 2 to low?

 

[hgoncalves]

Hi,
After resoldering both coils, everything is shorted again (40ohm on every pad). After lifting both coils, everything goes to normal values.
I can only assume that the coils have some kind of problem. Am I right?
If so, where can i take similar coils on this board (the board that i have for parts, doesn't have those coils anymore)

 

[2informaticos]

27 ohm is good value.
Resolder coils and check diode mode to ground at PPBUS_G3H.

 

[hgoncalves]

Hi,

I have 26.60 ohm on every pad, and no short on PPBUS_G3H (15 k ohm) and 0.450V on diode mode.

Can i try to power it on?