So I have on the bench an 820-2936 tonight and It has me stumped. With board only out on the table, when I plug in a MS I get no PP3V42 but has a light, PPBUS_G3H is 2.6V. On U6990 I'm getting 18v on pins 4 & 7, but no PP3V42_G3H. I replaced U6990 and at first it seemed to work, had MS light, PP3V42 was present as well as PPBUS. After a few min I tried to turn it back on and nothing. Just a fading green light. It seemed like I fixed it but not back to not working. I tried to trigger SMC_ON/OFF_L but nothing happened.