I'm revisiting a rabbit hole repair that I have had on my shelf for a while. There was suspicion of a dead SMC (12.2v and not 12.6v). But I'm leaning more towards a short to ground somewhere. Currently building a bench power supply to inject current, should be done with it in about a week, waiting on parts.
In the mean time, I'd like to compare some measurements, diode mode with a known working board. However, I don't have a known working board handy. So I was hoping someone here might have one, or at least know off hand what measurements to look for.
Back story is, customer's power adapter, a generic one, fried a few things on this board. A few things replaced included R6990, D6990, U6990, U7000 ... among other visibly damaged resistors in the area.
Plug it in, green light comes on for 1-2 seconds every 15 seconds or so.
PPDCIN_G3H 18.6v. But it drops every few seconds constantly.
Remove R6990, diode mode measurement is 1.780 on pin 1. Zero on pin 2.
PP3V42_G3H - 3.42 and steady.
SMC_BC_ACOK - 2.5v (low?)
SYS_ONEWIRE & ADAPTER_SENSE @ U6900 - 2.88v
PP3V3_S5 - 3.33v steady.
PM_SLP_S4_L - 0v (suggests smc problem maybe or ??)
PP5V_S5 - 5.01v steady.
PPBUS_G3H - 12.2v steady.
What gets me is PPDCIN_G3H dropping every few seconds. Short to ground??
Anyway ... quitting time for me, back tomorrow. Anyone up for a little input?
Chuck
In the mean time, I'd like to compare some measurements, diode mode with a known working board. However, I don't have a known working board handy. So I was hoping someone here might have one, or at least know off hand what measurements to look for.
Back story is, customer's power adapter, a generic one, fried a few things on this board. A few things replaced included R6990, D6990, U6990, U7000 ... among other visibly damaged resistors in the area.
Plug it in, green light comes on for 1-2 seconds every 15 seconds or so.
PPDCIN_G3H 18.6v. But it drops every few seconds constantly.
Remove R6990, diode mode measurement is 1.780 on pin 1. Zero on pin 2.
PP3V42_G3H - 3.42 and steady.
SMC_BC_ACOK - 2.5v (low?)
SYS_ONEWIRE & ADAPTER_SENSE @ U6900 - 2.88v
PP3V3_S5 - 3.33v steady.
PM_SLP_S4_L - 0v (suggests smc problem maybe or ??)
PP5V_S5 - 5.01v steady.
PPBUS_G3H - 12.2v steady.
What gets me is PPDCIN_G3H dropping every few seconds. Short to ground??
Anyway ... quitting time for me, back tomorrow. Anyone up for a little input?
Chuck