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A1311 late 2009 820-2494A only 1 led non starting

E

ex250

New member
Hello guys, I have this one with a non-starting failure, on board diagnostic led 1 lights ok, tested with other know working power supply to discard, same behavior.

the S5 lines read:

PP1V1_S5_REG -> 1.11V

PP3V3_S5_REG -> 3.37V

PP5V_S5_LDO -> 4.98V

PP12V_S5 -> 12.01V

Seems this are all ok

This one not, too high reading, maybe the same culprit:

PGOOD_1V1_S5 -> 3.37V (should not be 1.1V?)

I was thinking that the U7300 could be the problem, as reading here on some other similar faults, but replaced it 2 times and all is the same.

Any guidance would we appreciated, this is making me crazy.

Regards
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

U7300 is the first suspect on this model.
However, before change it, check if gets proper voltage and signal to work.
Trigger SMC_ONOFF_L signal and check U7300 basic voltage; pins 11, 10, 1.

"PGOOD_1V1_S5 -> 3.37V (should not be 1.1V?)"
Don't make confusion between a power rail and one of its related signals.
Do you expect to get 1.1V on all U7950 pins with "1V1" included in the signal/power name???
Don't make wrong assumptions so easy in the future...
 
E

ex250

New member
Many thanks!

Sorry for the mistake, I'm still learning, I do not distinguish well the nomenclatures used on this boards.

U7300

Pin 11-> 12.08v
Pin 10-> 5.15v
Pin 1-> 3.36v
 
2informaticos

2informaticos

Administrator
Staff member
Possibly bad chip.
If really good, then check all surrounding resistors and traces.
Also check C7306 and D7301.

Be sure to solder U7300 properly; this board has lot of copper, not easy to heat.
Scratch chip pads and apply leaded solder on them (including laterally) before placing it on the board.
You must get nice solder between board pads and lateral of the chip too.
 
E

ex250

New member
C7306 pin1-> 2.15v pin2-> 0v 1.1nF seems OK
D7301 Pin1-> 5.15v pin2-> 6.74v, at diode mode 0.160v and 0v

Will try again to solder the chip, I preheat the board a little to make easy the solder
 
2informaticos

2informaticos

Administrator
Staff member
U7300 gets power and enable; so should generate 5V_S3.

For surrounding components, I was expected that you check their values (ohm scale; out of board, if needed).
I didn't ask for diode mode to ground on them.
Diode mode to ground on L7320 yes, must be checked.
Be sure all traces and solders are good.
Check U7300 again...
 
E

ex250

New member
Hello, will work around, soldered a new one again, and same.

L7320 -> 0.118

R7301-> 99.9K
R7302-> 24.89K
R7304-> 0
R7305-> 7.70K ?? (43.2k)
R7306-> 6.8K ?? (8.06k)
R7310-> 9.92K
R7311-> 101.1K
R7312-> 38K ?? (100k)

Should any of the ?? ones to be desoldered to check out the board?

The D7301 Pin1-> 5.093v pin2-> 5.071v

Many thanks for your advice
 
2informaticos

2informaticos

Administrator
Staff member
Value for resistors measured on board is lower than nominal; this happens for high values, K/Mohm.

If you get correct power input and enable signal for U7300, I can only suspect bad solders, or broken traces.

When I said "surrounding resistors", I was looking at schematic; some components can be placed on other side of the board.
You may need to replace Q7330/35 and C7326.
 
E

ex250

New member
Hello, unsoldered the Q7330 and the Q7335, both seems good on readings and gate enabling compared with new ones.
The C7326 reads 102,5nf (0.1uF) seems OK
 
E

ex250

New member
Two lots of 2 units from different sellers, latest ones came in bga sealed packets, tested all four with same results, just because of this I said this make me crazy. Any other thing to check?
 
2informaticos

2informaticos

Administrator
Staff member
Nothing more that already said.
If chip gets power and enable then must work, if all related components and traces are good.
If not, bad solders....
 
E

ex250

New member
The U7300 gets some hot when powered, around 38C quickly, and also the U1400, if the 7300 was bad, should not heat up? not?
 
2informaticos

2informaticos

Administrator
Staff member
What is actual diode mode reading to ground at L7320?
Do you still get 5VREG_EN (after pressing power button)?
 
E

ex250

New member
Yes, I have the 5VREG_EN at 3.36v

L7320 -> 0.108

U7300
v diode
P1 -> 3,36---- 0,568
P2 -> 4,55---- 0,728
P3 -> 2,66---- 0,726
P4 -> 0 ------ 0,721
P5 -> 0 ------ 0,112
P6 -> 0 ------ 0,827
P7 -> 5,089-- 0,582
P8 -> gnd --- 0,001
P9 -> 5,089-- 0,669
P10 -> 5,089-- 0,582
P11 -> 12,09-- 0,528
P12 -> 5,067-- 0,64
P13 -> 0 ------ 0,774
P14 -> 0 ------ 0,112
P15 -> 5,089 -- 0,734
P16 -> 1,25--- 0,733
 
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