macbook 820-2849 PP5V_S0 shorted

Laimis

New member
Hi need some advice, board 820-2849 PP5V_S0 acting strange. need to find out where its shorted to ground. If i take RC215 off then pin 2 shows beautiful 5.02V and pin 1=2.27v , what i dont understand where does it take 2.27v when rc215 is off as UC240 is no stuff. As soon as i put it on 5V disappear leaving pin 2 with 0.05V. If i inject 5.5V to pin 1 then fans starts spinning and 5v stays as if its not shorted at all nothing gets warm. any ideas where to look at?
 

Laimis

New member
find out that something at PP1V05_S0_PCH end shorted to ground as two L2560 and L2565 had a crack. removed them and both pins 1 had a continuous beep 0.05 diode mode. Trying to find out what makes PP1V05_S0_PCH but cant find it. any suggestions.
 

Laimis

New member
Hi, found some time to play with the board again. sorted out the short on PP5V_S0, it was a poly tantalum capacitor. Now the board turns on, but PPVCORE_GPU Missing. Power comes to U8900 anything particular to look at ?
 

Laimis

New member
hi mate, where are you from duke? you're always here. glad you're always happy to help. yes mate EG_RAIL3_EN is present. vcore GPU was shorted so removed the L8920, still nothing, replaced u8900. i have 4.6V on Q8951 pin5 lgate, 0 V on Q8950 pin4 ugate, pins 1256 -8.6V
 

Laimis

New member
ok so the board turns on fans spin but no chime no video. if i measure voltage on PPCPUVTT_S0 when board is powered on i get 1.05V so its fine, then when i measure PPVCORE_S0_CPU i get 0.8V and its supposed to be 1.25V right? does it mean it is shorting somewhere? most of the time when i plug charger i get green light but it doesnt start but unplug it and plug it straight away and it powers on from second time. doesnt power on from 1st attempt. when pluggged in for the first time i get 0.36V on PP5V_S0 so fans dont spin but unplug it and plug it straight away and fans start to spin with 5V on PP5V_S0. Resistance to ground on L7425=051 is it normal? thanks for your time duke
 

dukefawks

Administrator
Resistance to ground on L7425=051

I have no idea what 051 is. Also need to know resistance to GND on PPVCORE_GPU if that rail is not present.
 
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