(347) 552-2258 [email protected]

A1398 820-3071-A with no image

H

hgoncalves

Active member
Hi,

i have an A1398 820-3332-A, that seams that powers on, has a chime, but has no image, even on an external monitor.
I know that this models are known to have a an GPU problem. How can i make sure that the problem is on then GPU or in somthing else?

What should i measure?

Thanks!
 
Last edited:
H

hgoncalves

Active member
OK, i notice that someelse has already been on the board and the U8900 has a jumper from testpoint GFXIMVP_DPSLP_EN to pin 39 of the U8900. I get 0V on that test point. Does this means anything?

Should i continue to reball U8900?

P.S. the client says that he bought it refurbished, but was working until now
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
You did something wrong, maybe to much heat affected CPU.
Try replacing U8900.
Be sure to get good solders.
 
H

hgoncalves

Active member
I resoldered the U8900 again and now it has a chime, but still no image. I don't have another 820-3332-A to take out the chip. Can i take from other board model?
 
2informaticos

2informaticos

Administrator
Staff member
Do you get now voltage at GPU coil?
If not, check diode mode and post U8900 voltages; pins 2, 12, 13, 19, 20.
 
H

hgoncalves

Active member
Unfortunently, it stoped working by it self. It was working for the lunch period (board mounted in t the laptop with the cooler), and stoped working out of the blue. Now it has green light, but doesn't chime, no fan spin, and consumes 280mA.
Any idea?
 
H

hgoncalves

Active member
Hi, 280mA seams to be something related to the CPU. Do you think that it is the CPU? I don't think that i've overheated it...
 
2informaticos

2informaticos

Administrator
Staff member
0.46V at iGPU core is good voltage.

I asked you about GPU VCORE, not Intel..
Pay atention in the future about the questions.
U8900 is not even powered, that's the reason of missing GPU voltage.
Check schematic and fix problem with pins 19 & 20 first.
 
H

hgoncalves

Active member
Hi,
I´ve tried but i can't figure it out

I think that the problems are in PPVIN_S0_GFXIMVP because it has only 1.2V and schematics says the it should be 12.8V, and on =PP5V_S0_GFXIMVP that should be 5V and is 0.48V.

Also don't have =GPUVCORE_EN from U9100 test point.

I tried to follow the schematic to find the cause, but i couldn't... can you give a clue from where to start?
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
I don't know what schematic I was looking before.
U8900 is powered at pins 16, 17 & 25.
First check for short all them.

Check R5410 and traces.
Also check Q7860 and its voltages.
 
H

hgoncalves

Active member
Hi. Thanks for the reply.

U8900:

16 = 0.30V | 0.406v on diode | 9 K ohm resistance to ground
17 = 1.2V | 0.018v on diode | 10 ohm resistance to ground
25 = 0.30V | 0,470v on diode | 7.5 M ohm resistance to ground

R5410 has 1.2V on all 4 pads

Q7860 has 0V on all pins

PPBUS_G3H = 1.3V

Any idea?
 
2informaticos

2informaticos

Administrator
Staff member
You said to get a lot of voltages on the board.
Now missing PPBUS_G3H voltage???

I bet for shorted MOSFET on GPU power supply.
Compare ohm value to ground at PPBUS_G3H with GPU core coil.
 
H

hgoncalves

Active member
Yes, before i soldered U8900 again, it had voltage (even chime). After the U8900 all is gone and it consumes only 280 mA in PS.

PPBUS_G3H = 0.60 ohm

L8930 = 0.33 ohm (not sure if this is the GPU core coil)

R7020 has 19.8 V but on F7040 and on R7050 only has 1.3V. On my boardview i can´t find the D6990
 
2informaticos

2informaticos

Administrator
Staff member
Did you power up the board without U8900???

Lift L8930/60 and check again resistance to ground at PPBUS_G3H.
 
You must log in or register to reply here.
Top