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820-00165 with water damage(screen connector area looks clean), IO board replaced, cleaned the corrosion and the machine booted up. Survived MacOS install. An hour later the screen died(have backlight + white horizontal lines). Used external monitor and it output OK. Tested dead screen with...

original 60w magsafe known good adapter(tested), machine used to work but has been in storage for 2 years. No liquid damage. PPBUS_G3H = 12.24V PP3V42_g3H = 3.4v PP3V3_S5 = 0V PP5V_S5 = 0V SMC_RESET_L = 3.37v SMC_BC_ACOK = 3.2v now what?

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...

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

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?

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?

LED601 on. Checked SMC_ONOFF_L toggle 0v/3v but board does not respond. problem with SMC?

without battery, when 1st plug in, I can hear the chime but screen is black and the fan will spin up for 5 seconds before it repeat, when it repeats, I hear no more chime. when plugged a battery, it will boot up, sometimes normal speed and sometimes very slowly, and it wont charge the battery...

Seems no liquid damage. But USB-C to magsafe converter were used before it is dead. where to start?

This wont turn on, without ram it wont beep (good known one will beep without ram). where to start?

Only those sensor with check marks passed the test, the others (IDSR, PDSR, Tp1P, Tp2H, Tp3H, VDPr, VDSR) reported either sensor value problem or SMC error.

No chime. MacOS will not detect any audio devices (settings no mic/in/out). Where do start?

Minor corrosion around U8300 and U3210 and cleaned by some flux and hot air. The board will chime but no display whatsoever via LCD nor thunderbolt port. where to look?

So the IO board was completely dead with no usb whatsoever, after replacing it, the USB is back but wifi still not working, wifi card tested good on another computer. where should I look?

Without ram, the iMac will beep. Put the known good ram in, it will turn on with only LED1&2 and Fan. No Chime. No USB. Where should I start looking?

board has garbage distorted screen due to vram issue. Reflowed vram and screen come back OK. Backlight is OK. when close lid, the machine will go to sleep, but screen wont come back when lid is open. Actually there are stuff displayed on the screen and can be seen when shine light from apple...

Removed F7040. when plug real charger, pin 1 slowly drop from 12.5v and then cycling. When plug in fake charger, pin 1 dropped from 12.5v to 0.1v and stay there.. .

Board has liquid damage with obvious corrosion around C7272/C7273 and also around F7040 area. Green light. No fan spin. U7200 generates PP5V_S5 and has 5V when measured at pin 1 of C7273. However, when measure the same PP5V_S5 at C7801, it is only 3.05V. But when I tried to measure the...