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820-3115 no PPVCORE_S0_CPU

Bouba148

Bouba148

New member
Hi Team,

This board came as dead with no green light , no ppbus_g3h, broken traces around U7000 missing of a lot of small components like inductors and capacitors :C9015, L9004, L9400, C9401, C4319, L9499, C1699,C162E, C169E, C1695.
After solving all this now the board is starting with the fan spinning to the max speed, no ram beep, no chime no display.
USB Mouse turning ON (red)


PP1V5_S0: 1.509V
PP1V05_S0_LDO: 1.056V
PP1V8_S0:1.0803V
PPVCORE_S0_CPU: 0V
PPVCORE_S0_AXG: 0V
PP1V05_S0: 1.052V
L2406:1.052V
PP1V5_S3_CPU_VCCDQ: 1.506V
PP1V05_S0_CPU_VCCPQE: 1.055V
PP1V8_S0_CPU_VCCPLL_R: 1.795V
R5510, R5511 and R5512: OK

Resistance between Pin 3 and Pin 6,7,8 is 2.5Ohm at Q7550, 7.7 Ohms at Q7510 and 6.6Ohms at Q7520

I would like to replace Q7510 Q7520 Q7550 and maybe U7400 to try to restore PPVCORE_S0_CPU and see the fan speed later........
What do you think?
 
Bouba148

Bouba148

New member
Hi Jadao, thanks for replying

I've checked check R7402 / R7403 both are ok but I've replaced R7412 because this one wasn't in good shape and it's resistance was more than 5 MOhms.....
I've also reflowed all the U7400 area, but it's still at the same point.

I'll pass it in the UC and get back to you guys, in the mean time if you have any suggestions, they're welcome.....
I'm still waiting someone to confirm me to replace or not Q7510, Q7520, Q7550 and U7400.
 
2informaticos

2informaticos

Administrator
Staff member
Ceck first if U7400 is correctly powered up, pins 19, 29, 46.
It also needs 3V at pin 47.
At pins 1 & 48 you should see some drop pulse at least, if U7400 tries to start.
Do you get SYSCLK_CLK25M_SB (25MHz) from U2600?
Also check all resistors and traces around SPI chip U6100.
Finally, try new BIOS dump...
 
Bouba148

Bouba148

New member
At R7401 I have 5.085V on Pin 1 and 5.087V on Pin 2 so U7400 is powered correctly checked also directly on pin 45/46 and pins 19/26 to avoid broken traces.
and I have 3.312V on Pin 47 so U7400 is being told to turn ON.
On pin 48 I have a solid 12.37V and 12.33V on Pin 1.

At U2600 I have 25Mhz clock signal

Between U7400 and U6100 I've noticed that R7404 was missing so I installed an other one

Now I have:
PPVCORE_S0_CPU_PH1: 1.212V
PPVCORE_S0_CPU_PH2: 1.197V
PPVCORE_S0_AXG: 0V

This time the board turns ON and it beeps when no ram is installed, but if I install a Ram memory I have NO display and the fan spin for around 5 seconds then stop in loop.
If I touch the U5511 area it's really hot, it's just behind the CPU.....
 
Bouba148

Bouba148

New member
Question why 10600S and not 12800S? It's very interessting what your asking because:

With any 12800S ram in any slot it's starting for almost 5-6 sec then stops in loop same in smc bypass mode.

Without ram or with 10600S in any slot , fan spin non stop to the max and i've noticed the L7510 and L7520 are burning hot and can't keep my finger on them more than 1-2 sec like if the CPU is comsuming too much power, of course without the heatsink the machine stops after the fan reaches the max speed and I guess the over temp limit.

My guess maybe dead CPU.....but i'd like to have the experts point of view and also maybe any more steps to check in the troubleshoot process.
 
2informaticos

2informaticos

Administrator
Staff member
Any USB activity?
Normally VCORE should follow the sequence 1.1-0.95-0.85V...
AXG should appear with apox 1V and drops to 0V in few seconds.

Possibly bad CPU if gets very hot so fast.
 
Bouba148

Bouba148

New member
Yes USB Activity ( mouse red light ON ) ......which means please?
VCORE Stays at solid 1.25V
AXG Stays at 0V never goes at 1V
 
2informaticos

2informaticos

Administrator
Staff member
If VCORE doesn't drop to 0.8V aprox in 2-3s, then board is not working.
Apart of mouse light, can you see flashing light for an USB OSX pendrive?
AXG should appear just in the first seconds when board is powered and disappears completely in 3-4s.
 
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