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PM_RSMRST_L is kept at high. But trigger SMC_ONOFF_L cause NO drop at PM_PWRBTN_L. Always stuck at 3.4v

3V3_SUS is present. RTC_RESET_L = 3.3v PCH_SRTCRST_L = 3.3v PCH_INTRUDER_L = 3.052v PCH_INTVRMEN = 3.23v I just measure these voltages directly while it is powered, do i need to trigger anything while measuring these?

Board looks clean, except there is some tiny corrosion around TP SPI_MSIO_R, no short there. PP3V42_G3H = 3.42V PP5V_S5 = 5v PP3V3_S5 = 3.3v AVREF_SMC = 3.3v PP5V_S3/PP3V3_S3 not present. triggered ONOFF (short pad R5115/16) and no pulse at PM_SLP_S4_L = 0V. PCH_DSWVRMEN = 3.2v PM_DSW_PWRGD...

CPU is currently removed from a 820-2784 that wont turn on. S5 rails are present and I do see LED1 on. However, P5VS3_EN is 0v, do I need to put back the CPU for it to turn on? Or can I continue to troubleshoot without the CPU? The board arrived without heatsink and I dont have the heatsink...

you are correct once again, U7700 bad solder..removed and resolder again fixed this. Thanks!

u8000: PP12V_S5 pin 1: 11.92v PP5V_S0_EN pin 2: 3.3v PP5V_S3 pin 5: 0.4v PP5V_S0 pin 6: 0.4v P5V_S0_EN_G pin 7: 11.87v PGOOD_P5V_S0 pin 8: 1.25v

U6900: PGOOD_SYSPWROK_R = 0v PM_MXM_PGOOD = 3.3v ALL_SYS_PWRGD = 0v PGOOD_P12V_S0 = 3.3v PM_SLP_S3_BUF_L = 3.3v PCHCORE_PGOOD_R = 3.3v PM_SLP_S3_B_R = 3.3v S4_ENABLES = 3.3v PM_SLP_S4_1_L = 3.3v

removed CMOS cell, still only have LED601. PM_SLP_S3_L = 3.3v whats wrong now?

ok U7700 replaced, now LED601 is on. I now have PP3V3_S5. However, it wont respond to power on if I short J5010. I saw SMC_ONOFF_L goes low from 3.4v to 0.3v when i short J5010. PM_SLP_S3_L is 3.3v.

i can only find a few big coils but they dont seems to have short.. Here are some measure of voltages: PP12V_G3H = 12v PP3V42_G3H = 3.4v PP12V_S5 = 12v PP5V_S5 = 5v PP3V3_S5 = 0v. (NO short to ground)

Used known good PSU, Diagnostic LED601 will intermittently blink after a few try but won't stay on... where should I start?

sorry my bad, i find out i used cards from other years all along... although those cards work but they are not the original card used in this particular model and hence probably why Catalina didnt initialize them or something.. Now i installed Sonoma/OCLP and the wifi is working.

Board 820-3481A iMac 2013 27" with unknown history. Board seems clean. Tried to replace a few known good airport card but all of them have bluetooth detected but WIFI not detected. Schematics is not available but 820-3478A wifi/bt area seems to be the same... where to start?

seems like i am getting intermittent result... i also tried to test this on a macbook logic board and the result are different.. all leds supposed to be on (weak) with a few brighter i guess?

half of the leds are off (i am guessing because those are for the other side/edge?) half of the leds are on and weak and 4 are brighter than others Do i need to test all 4 slots? I will need to remove the button battery and extend with wire as it block the space....

Trying to figure out how to use this, without power plugin and this card in one of the slot, I saw only 4 bright leds… am I doing this correctly? What does this tell?

This?

tested with good known ram and connected with only fan, power and left speaker with everything else disconnected.. I also disconnected RAM sticks and it gives me 1 beep in this case. Put it back, 3 beeps. Unknown history.... where to start?

Changed another new chip LTC3851EUD fixed it. Many thanks!

i used a new LTC3851EUD chip... For Q7330/5. I cannot find CSD5886, is there any other replacement chip that i can use?