Hi all, the A1990 board I have is taking 20v but cycling 50ma and I have hit a wall in troubleshooting. I can't find any shorts anywhere and I have tried configurator 2 with no luck on reviving it. The only area getting slightly warn is the T2 chip. Would that be what is bad or should I keep looking for a short somewhere. I have gone through all the rails. What circuit most likely is stopping the boot process at 50ma? Any help would be very much appreciated. Thank you!
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Re: 820-01041 20v and cycling 50ma
Cannot vouch for the T2 warming but let us ignore it for now.
Remove all power. Meter in resistance mode.
Check the resistance to ground for each coil. Interested in any low resistance readings that may indicate a fault on that rail.
Next, with power to the logic board - do you have a steady PPBUS_G3H rail @ F7000? What is the voltage on F7000, pin # 2 ? If no voltage here, what about pin # 1 ?
Check the voltages on:
I2C_PWR_SDA
I2C_PWR_SCL
SMBUS_3V3_BATT_SDA
SMBUS_3V3_BATT_SCL
You may have an excessive current draw that is causing components like U7000 to enter chirp mode to prevent damage. Or U7000 may be missing current sense resistors that in a loop gauge the downstream load current. If the loop is broken due to a missing or damaged current sense circuit, then U7000 will believe that too much current is being drawn so shuts OFF - hence the power cycling. -
Re: 820-01041 20v and cycling 50ma
Thank you so much for your reply and help.
Resistance is low only the coils around CPU and GFX VCCs. 10ohms and less. The rest are no where near that low.
PPBUS_G3H is very steady at 12.62V on both sides of F7000.
Voltages on requested points:
I2C_PWR_SDA- 1.8v
I2C_PWR_SCL- 1.8v
SMBUS_3V3_BATT_SDA- 3.3v
SMBUS_3V3_BATT_SCL- 3.3v
Haven't found any missing current sense resistors at this point. I will keep examining to see if something else shows itself though.
Thank you again.Comment
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