A1466 820-00165-A no power

Hi,

I have an A1466 820-00165-A that seems to have a bizarre behaviour. The client says that the mac sometimes, doesn't power on. Here it was working, without any problems, for 3 days (several power on and power off), and on the fourth day it didn't power on.

After I disassemble the board to diagnose, the board start working again without any problem, and all the measures seem to be ok (because it is powered on i assume).

I mounted the equipment on the unibody, and the problem happens again after 5 days without any problems, until it stooped, and on the bench it works again.

Do you have any idea? What should i check from here?

Thanks.
 

2informaticos

Administrator
Staff member
This kind of behaviour, is a nightmare.
You cannot get an immediate feedback, after something done on the board.

What the client commented about how the fail appeared?

You will have to test the board many days after any work done on it.
Try first getting known good working battery.
 
Hi,

Already tried with a working battery.
the client says the it started happening with no reason.

I notice that the U1900, C1902 and C1905 had a little corrosion, and i've replaced all, and the Y1905.
After that, i have green light, but no fan spin and no power (20 mA on PS).

On U1900 i get:

1 = 76 kohm
2 = 9kohm
3 = 4.1 M ohm
4= 4.9 Mohm
5= 8.9 kohm
6 = 8.9 kohm
8 = 4.8 M ohm
12 = 5 Mohm
13 = 8.5 kohm
14= 79 kohm
15 = 1.7 kohm
 

2informaticos

Administrator
Staff member
These OHM values are irrelevant.

We need some signals/voltages from power on sequence, when the board doesn't want to work.
 
OK, today, i don't even have a green light or fan spin.

0,40 A on PS.

PPBUS_G3H = 0.7v
PPDCIN_G3H = 19.0v
PP3V42_G3H = 0.12v
 

2informaticos

Administrator
Staff member
Post U7100 voltages; pins 1, 2, 3, 9, 14, 15, 19, 20, 27.
Also check pins 6 & 8 de U7090.
Be sure D7012 is good, as all components around Q7010.
 
U7100 :
1 = 0v
2 = 19.7
3 = 5.2
9 = 0.02
14 = 0v
15 = 0.05v
19 = 5v
20 = 5v
27 = 19.5

U7090 :
6 = 19.1v
8 = 19.1v

D7012 is ok and everything around Q7010 seems to be ok
 

2informaticos

Administrator
Staff member
"shorted 3V42_G3H = 0.0v on diode mode"
When the short disappeared???

I suppose 0.300 in diode mode, which is correct.
If really 0.3 ohm, then still short...
 

2informaticos

Administrator
Staff member
0.21 ohm means 210 miliohm, something MUST get hot when injecting voltage.
Unless you set amp limit too low, blocking lab PSU.
ALWAYS set amp limit to max, for voltage injection.
 
I set my PS to 5A (the max), and even so it only consumes around 1,3 A.
Not even with the thermal cam i found anything hot.

Maybe i did something wrong. I'll try again
 

2informaticos

Administrator
Staff member
3V into less than 1 ohm, you should get higher current.
Use ticker cables to connect lab PSU.
Start injecting with 1V and go high slowly; no more than 4V.
 

2informaticos

Administrator
Staff member
You cannot set the injected current!!!
The current depends by injected voltage and short ressistance.
Be sure to set amp limit to max, nothing else to adjust for current.

If boards takes 2A with 4V, that means 8W; something MUST heat.
Remove the heatsink first and use ticker cables for the lab PSU.
And start with lower voltage; or the PSU will get blocked before injected anything.
 
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