I'm having a hard time with this particular board. It's an 820-2850 with no power:
1. PPBUS_G3H bounces from 12.6v down to 0v, then back up. SMC_PM_G2_EN is also pulsing, as are my S5 rails.
2. PP3v42_G3H stable at 3.42v. Green light solid.
3. Resistance at U7000 (17/18, 27/28) is normal (~3ohm and ~20ohm). Pin 3 of U7000 solid (does not bounce/fluctuate).
4. No power from charger or battery, however, PPBUS does NOT pulse when a battery is connected only (i.e., with battery plugged in, ppbus stays steady), however, the board still will not power on with battery.
5. I can't find a short anywhere; I've checked pp3v3_s5, pp5v_s5, pp3v3_s3, pp5v_s3, pp5v_s0, pp3v3_s0, pp1v05_s5, PPBUS, PP3v42, etc. Couldn't find a short anywhere that might be causing the board to cycle.
6. SMC_RESET_L is stable at 3.4v, however, it drops to 3.3v for a split second every time the board cycles/rails fluctuate.
7. I replaced the SMC, but no change.
8. I replaced U7000/Q7030/Q7035 simultaneously (pin 23 fluctuates, but pin 3 does not, so I thought maybe U7000/Q7030/Q7035 were having issues), but no change.
9. R7020/R7050 measure fine.
Really at a loss on this one. I'm still leaning towards a short somewhere, but I don't know where else to check. Any help with what direction to go would be appreciated--thank you as always!
1. PPBUS_G3H bounces from 12.6v down to 0v, then back up. SMC_PM_G2_EN is also pulsing, as are my S5 rails.
2. PP3v42_G3H stable at 3.42v. Green light solid.
3. Resistance at U7000 (17/18, 27/28) is normal (~3ohm and ~20ohm). Pin 3 of U7000 solid (does not bounce/fluctuate).
4. No power from charger or battery, however, PPBUS does NOT pulse when a battery is connected only (i.e., with battery plugged in, ppbus stays steady), however, the board still will not power on with battery.
5. I can't find a short anywhere; I've checked pp3v3_s5, pp5v_s5, pp3v3_s3, pp5v_s3, pp5v_s0, pp3v3_s0, pp1v05_s5, PPBUS, PP3v42, etc. Couldn't find a short anywhere that might be causing the board to cycle.
6. SMC_RESET_L is stable at 3.4v, however, it drops to 3.3v for a split second every time the board cycles/rails fluctuate.
7. I replaced the SMC, but no change.
8. I replaced U7000/Q7030/Q7035 simultaneously (pin 23 fluctuates, but pin 3 does not, so I thought maybe U7000/Q7030/Q7035 were having issues), but no change.
9. R7020/R7050 measure fine.
Really at a loss on this one. I'm still leaning towards a short somewhere, but I don't know where else to check. Any help with what direction to go would be appreciated--thank you as always!