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Right have looked at the power on sequence and it's getting stuck at PMU_ONOFF_L - it drops from 3.3v to 0v when power button pressed but PP3v3_S5 and PP1v8_S5 do not pulse or appear after this. I have got PP5V_S5 present still though

Right i've replaced U9080 now and I am getting SSD voltages but the machine is still not powering up. I'll check the power on sequence!

cannot see any SSD voltages coming up - with a new battery connected it's not really made any difference - my USB C meter is showing it hovering up to 0.5a and then back to 0A then looping back up to 0.5A draw again. CPU isn't getting warm and no voltages coming other than S5 ones

Nailed it thanks! Q6000 was missing as was a couple of resistors next to it. Replaced from a donor board and fans behaving normally now. Just got to sort out the customer with a new Touch ID flex cable!

Got an 820-01949-07 in today - problem is it won't start up - stripped it down to just the board and charger and it takes 20V 0.09A current draw. Popped it under the thermal camera and the only thing which is heating slightly is U9080 - nothing visible shorted on the NAND power lines either...

So i got an 820-00850 in today - was originally fully shorted out stuck at 5V which I identified to a burned cap. Now the board turns on and works fine but the left fan as looking at it from the bottom runs at absolutely full speed (right one working normally) and also continues to run after the...

Did a bit more checking - soldered U1930 upside down with jumper wires to confirm connections were good and same behavior. Only thing I can think of is there's a CPU issue - it's reading 10ohms to ground on the Phase 1 power rail. Going to pop this one on the unrepairable pile and sell the...

Checked U1930 again - replaced it again from another donor board and behavior is the same. With it out i'm getting ALL_SYS_PWRGD, PM_SLP_S3_L and all S0 voltages. With it there get a small pulse on ALL_SYS_PWRGD and then the board reverts and stays in S5 state. Board does absolutely nothing in...

Posted this in the wrong section by accident somehow so apologies for that! Reposting here: Got an 820-00165 here on the bench which is causing some confusion. Green Light is there which turns orange as normal, ppbus present 8.6V. Visual inspection revealed tiny amount of corrosion around...

Got an 820-00165 here on the bench which is causing some confusion. Green Light is there which turns orange as normal, ppbus present 8.6V. Visual inspection revealed tiny amount of corrosion around u1930 - pulled this off replaced from a donor board and still no power. Pulled it off again and...

Yes it works perfectly with the known good battery, charges, runs off it, reads the battery % and cycles no issue there. Quoted customer for a replacement battery and fitted it machine is done now. I may in future open up the old battery and see if I can find anything wrong with it!

Thanks once again - nailed the issue in one. Checked U8030 had 3.3V on the input side ok, looked then carefully at U8030 under the scope and saw a tiny crack on one edge of it. Pulled a replacement from a scrap 820-3437 and system works perfectly now, starts up, chimes boots only other issue is...

so i've got an 820-00165 in which had no power - I located a short on PPBUS_G3H and blown F7140. Located the short down to a shorted out cap and replaced, also replaced F7140 after confirming there was no further short. Board powers up enters S0 state has fan spin but CPU VCORE is missing also...

I've tried an old broken screen from an A1706 - still no picture. I've ordered a new U9850 to try - i've done a bit more checking around and am not getting any voltage on L7410 or L7420. I presume these are for the CPU's internal GPU? The other coils are reading normal voltage - cpu ones 0.8V...

So i've got an A1990 with I think it's 820-01041 (will have to double check that) board. It was liquid damaged top area of the board above the cpu. Also the main screen cable was not damaged but the backlight cable which goes from the screen on one side was corroded. I have replaced the...

Ultrasonic the board then try again - theres probably crap underneath one or more chips.

Solved - in the end it was a bad U8330 - once replaced, display backlight and image are back as normal.

There is no 5v coming there at all not even for a few seconds. What is the next step?

Got an 820-3536 in today with no display. System chimes as normal but there is nothing on the internal screen. Visual inspection revealed some liquid damage on the JTAG connector which has been cleaned up, i've also cleaned the screen connection and tried another LCD - still no display. I'm...

Ok so i heated the 12V_S5 mosfet and it worked for a bit then stopped again. I've now replaced it and the iMac is working normally again. Thanks for the advice!