Sorry to hijack this thread, I have the same board with a similar problem. First one of the CD3215's was dead, no voltage on USB meter. Replaced faulty CD3215 and now get 5v climbs quickly to 12v around 200ma then loops back to 5v then loops at 5v most of time. Very low PPBUS ma reading but pp3v3_g3h present. I have replaced ISL and diode which takes battery and PC DIN. It seems there is a short before machine fully boots but struggling what to look at next. Hoping CPU not fried, I have replaced 2 cracked tantalum capacitors which were cracked ( think this was the cause originally ) no water damage, clean board otherwise and no other visual damage under microscope.
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Are you using a suitable power adapter that offers 20V as a power delivery contract? Re: PPBUS - remove the downstream fuse(s) and then power up again. Without the fuse(s) on PPBUS_G3H, is the ISL side (producer) stable? What is the voltage to ground without a load? -
Hi Mon2 sorry I didn't get back to you straight away, I removed R7000 and R7001 and the voltage jumped to 20v! checked again for shorts on the upstream side and nothing, then before I had chance to do anything all 4 CD3215's back to 5v? I have since replaced ISL, D6902 & U6903 and have 2 of the CD3215 kind of cycling and 2 at 0amp draw. Also PM_EN_P3V3_G3H is 5.06v?
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PP3V3_G3H = 4.472v?Comment
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That is a too high of a voltage. Very concerned about damage to the other logic on this 3v3 power rail.
This overshoot of the output voltage is linked to the incorrect feedback resistors (R6910-R6913) on the buck regulator @ U6903. These critical resistors define the final output voltage of 3v3.
While it may be too late, consider to flux and remove R6923. This 0 ohm resistor will stop this high voltage from powering the same devices that are downstream. Then focus on correcting this power rail to become stabilized to 3v3. Do not add R6923 till this rail is @ 3v3.Comment
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Thanks for your response Mon2, I will give that a go and see if the voltage lowersComment
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