[SOLVED] MacAir wont start; blinking green/orange light {short to ground on 5v bus}

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elcapitan

Member
Hello, I have a MacAir 2011 A1370 BRD: 820-3024-B that doesn't turn on. It doesn't have any history of water damage. Every time I connect the magsafe (60W) to the computer it flashes green and orange very rapidly. I have taken some measurements and from what I can see the computer fails to switch to the S0 state due to a short on PP5V_S3. Please correct me if I'm wrong. I have tried to inject some voltage into this line to find the short but nothing is getting hot. I have checked the charging circuitry (U7000) and it looks ok. I don't have a good board to compare. Any ideas? Thanks!

PPBUS_G3H 8.35v (12.8v)
PPDCIN_G3H 17.06v (12.8v)
PP3V42_G3H 3.40v (3.42v)

PP5V_S5 4.80v
*PP5V_S3 0v
PP5V_S0 0.17

PP3V3_S5 3.32v
PP3V3_S3 0.24v
PP3V3_S0
 

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elcapitan

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If I switch my meter to beep test and put my red probe on 5v_s3 and my black probe on a screw hole it gives me 2.2ohms. It also beeps. Is this what you mean? From what I can see, 5v_s3 gets initiated from u7201. I have taken some measurements on this chip and it looks like it's missing en1. Should I try to inject some voltage on en1 to see if the machine turns on?
 

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elcapitan

Member
What is the resistance to GND on 5V_S3 then?

If I switch my meter to beep test and put my red probe on 5v_s3 and my black probe on a screw hole it gives me 2.2ohms. It also beeps. Is this what you mean? From what I can see, 5v_s3 gets initiated from u7201. I have taken some measurements on this chip and it looks like it's missing en1. Should I try to inject some voltage on en1 to see if the machine turns on?
 

dukefawks

Administrator
You need to find the short on the 5v_s3 bus first. There are MANY things connected to this bus so it is best to inject a voltage to the shorted bus and see what component is heating up. Start with 1V and slowly go up if nothing seems to heat. Do not go over 3V of course.
 

elcapitan

Member
You need to find the short on the 5v_s3 bus first. There are MANY things connected to this bus so it is best to inject a voltage to the shorted bus and see what component is heating up. Start with 1V and slowly go up if nothing seems to heat. Do not go over 3V of course.


Did I measure the resistance to ground correctly?
 
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