820-3209 P1V5CPU_EN giving me 3.3v

[jfursdon]

Hi

i have an old mac book air giving me 3.3v on P1V5CPU_EN I can see it is created from PP3V3_S3_MEMRESET so i can see where it gets it from but i dont see how it is supposed to be reduced. could some one please help i am tired of looking at page 62 of the schematic and not ubderstanding. thank you..

 

[JohnB8812]

That voltage is an ENABLE signal so 3.3 is fine. What is the problem with this board?

 

[2informaticos]

"i dont see how it is supposed to be reduced."
Wrong assumption!!!
3.3V is correct, as above mentioned.
Pay aterntion to ENTIRE name and do not confuse power rails with signals...

 

[jfursdon]

thank you for the replys
so green light going orange no fan spin
all power rails seem okay apart from
no all_sys_pwrgd
so from Q7950 I get
all_sys_pwrgd = 0.067V
PP1V05_SO_VMON=1.05V
PP1V5_S3RSO_VMON = 0.27V
VMON_3V3_DIV=1.067V
PP3V3_S5_VMON=3.3V
???????

 

[2informaticos]

"PP1V5_S3RSO_VMON = 0.27V"
Check if 1V5 _S3 rail is OK.
As per schematic, VMON Q3 BASE should be higher than 0.65V...

However, you can remove Q7950; not needed for good working.

 

[jfursdon]

sorry for not coming back sooner but lost half my roof in storm,
your right 1V5_S3 not present tested short and it went to 0 ohms. put 0.5v through the line at 6 amps nothing gets hot?? covered it in alcohol nada? any ideas?

 

[2informaticos]

If 5A limit bench power supply used, you are not injecting anything!
Start with lower voltage and increase it, maintaining ampers bellow limit.
Once 5A is reached, power supply gets blocked.
However such low voltage/power will not help you to heat anything.
You can remove CPU heatsink, but I doubt you'll detect something.

You can consider powerfull "injector"
https://www.ebay.es/itm/AC220V-DC-0...var=541593999842&_trksid=p2060353.m2749.l2649
If you can reach 1V/15A (as example), 15W should heat something there.

Removing R7350 can help you to locate the short, 1V5_S3 power supply, or RAM/CPU.