820-3332 No Power, Boiling Q8930

brunomotter

Member
Hello. Got this board that was turning on but giving constant KPs related to GPU. As it's a common problem on this model, I re-soldered U8900 and replaced some resistors/caps around U6201 as they were corroded. Now the machine does not turn on anymore. I noticed Q8930 was getting very hot, so I replaced it and at first time the board turned on, gave backlight but no VCORE/Video(brain dead). After I plugged off the power the machine did not turn on anymore and Q8930 started boiling again. I replaced it again alongside Q8931 and Q8961 as they were also gettin warm. Still no power and still boiling hot Q8930. I get only 1,5V on PPBUS_G3H and short to GND on L7030. If I replace Q8930 the short goes away, but as soon as I plug in the charger again the short comes back and Q8930 starts boiling. Any ideas? Dead GPU?
 

2informaticos

Administrator
Staff member
Re-check your job around U8900.
Bad solders, traces, or incorrect replacement components.
Pay atention to R/C8930, R8960, C8965.
 

brunomotter

Member
There was something stuck between pins 19 and 20 of U8900 shorting them. I cleaned, replaced Q8930 again and board turned on, but no VCORE and no GPU voltages.
 

2informaticos

Administrator
Staff member
VCORE should appear if Q8930 is removed; should even chimes the machine.
Do you get all other previous VCORE voltages?
 

brunomotter

Member
L7100 - 0.916V
L7630 - 1.063V
L8930 - 1.063V
L7330 - 1.334V
L7720 - 1.82V
L8310, 8360, 8930, 8960, 7560, 7550, 7510, 7520, 7530 all have 0V
 

2informaticos

Administrator
Staff member
I expected to check without Q8930.
As mentioned, VCORE should still appear then (even chime),

You've also said no GPU voltage and now posted to have 1V there (L8930).
 

2informaticos

Administrator
Staff member
OK, understood.
You should still try disabling GPU.
This may help to see if the short on U8900 damaged GPU somehow.
Post resistance to ground at L8930/60.
 

brunomotter

Member
L8930 - Black on GND, Red on coil - 27.5Ohm
L8930 - Red on GND, Black on coil - 25.5Ohm
L8960 - Black on GND, Red on coil - 23.9Ohm
L8960 - Red on GND, Black on coil - 25.5Ohm


Sorry for my ignorance, but how do I disable the GPU?
 

2informaticos

Administrator
Staff member
Both coils are tied together; sufficient to check one only.
In fact, just ONE measurment, as I asked for resistance (ohm scale), not diode mode.

Readings don't point to short.
Howeber, GPU got overvoltage through Q8930 few times, so is probably bad now.

About GPU disable, we have all the information on the forum.
 

brunomotter

Member
Did the steps to disable GPU. Still same issue. No VCORE. Backlight lights up as soon as I hit Power Button, but no chime or image.
 

2informaticos

Administrator
Staff member
If you've tested all mentioned steps, then GPU may block CPU somehow, or even CPU is bad.

Just in case, try known good BIOS.
Did you test with different RAM module?
 
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