[SOLVED] a1278 2936 low volatage on ppbus_g3h is 1.6volts

[djpat1974]

Hi, i have and A1278-2936 Board with green light at the charger.But ppbus_g3h is 1.6volts i even change u7000 and still same problem.What do you recommend? Please see my attachment for the rail i have checked.

 

[larossmann]

What is the resistance to ground on F7040? What is the resistance between pins 17/18 of U7000? What is the resistance between pins 27/28 of U7000? 1.7v is magic number for short to ground or bad charger side current sensing(pins 27/28)

 

[djpat1974]

thanks for your reply on f7040 to ground the resisitance in diode mode 0.423 current sensing (pins 27/28) is 16.31v and pin 17/18 i get 1.4v

 

[dukefawks]

Resistance between pins 17/18 and 27/28 not voltage.

 

[djpat1974]

Hi, i get 16.31v on pin 27/28 and i get low volts on pin 17/18 i should have 12.6 on pins 17/18 but i dont can you help me with this

 

[djpat1974]

is this short to ground i changed the ISL6259 twice and same issue.

 

[djpat1974]

pin 27/28 and i get diode mode 0.658 on pin 17/18 i get diode mode 0.001 i understand now

 

[dukefawks]

No you don't understand, I'm asking for resistance not diode mode. But diode mode provided enough info here. Pin 27/28 should have 20 Ohms between them. So you either have a bad R7021/22 or a bad trace in that circuit.

 

[djpat1974]

R7021/22 i get 10 ohms but on pins 27/28 i get 20 ohms and climbing up in ohms

 

[dukefawks]

Climbing up in not a value......

 

[djpat1974]

Yes climbing up not in value

 

[dukefawks]

I need a value, wait for it to stabilize. Anything over 22 Ohms will means bad R7021/22 or corroded trace.

 

[djpat1974]

okay thanks let me check

 

[djpat1974]

okay when i wait am getting 0.L meaning when i touch r7021/22 i get 3.200ohms then 0.L am not getting a reading

 

[dukefawks]

I have no idea what you mean. Check R7021/22 if they are 10 ohm and then check all traces from ISL6259 to R7021/22 and to R7020.

 

[djpat1974]

okay let me do that

 

[djpat1974]

okay i got some where wow you were right r7020 resistor had a bad trace that would not give me ohms reading on r7021/22 now i get 20 ohms after i made a jumper from r7020 i get now 12.6 and fan spins the only problem now mac come on then shuts off then comes on for about ten seconds i tried to smc reset and pram didn't work am thinking bios or maybe something i miss over look what you thing and thanks so far.

 

[dukefawks]

Are you getting voltage on L7510?

 

[djpat1974]

hi am back to try and fix this mac book pro again am getting no volts 0000.0 l7510

 

[djpat1974]

hi i remove the ram and the fan stays on then run a little high