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Safe mode -> chime, usb activity and video! Fan shuts off before can fully boot. (although I cant seem to repeat it) Then performed a reflow on U8900 - no change.

Loose screw inside case No liquid damage visible no usb activity all_sys_pwrgd. 3.3v pm_slp_s4_l 3.3v ppvrtc_g3h 3.3v pp3v3_sus 3.3v for 30 seconds until fn stops then 0v ppvcore_s0 0.8v pp1v05_s0 1.05v Thermal: CPU quick to get very hot (3seconds). PCH slow to get hot...

Can the graphics chip be disabled to leave a workable system using onboard graphics?

Is this problem a result of manufacturing like the older iMac graphics daughter boards that could be fixed by baking to remake solder joints? Is there any way to make a repair. I have already had the experience of purchasing a board that exhibited the exact same problem and had to be sent back...

In safe mode: progress increases to 50% point then sits for a minute or two then finally shows the login screen when I login I see a 30 seconds of beach ball, black background then says its rebooting because of a fault. instead of rebooting shows a black screen with moveable cursor. when I hold...

This iMac exhibits strange effects when transitioning from login screen to the desktop. Its a bit like a horizontal Venetian blinds being opened to view the fresh desktop. i.e. it paints the new screen in horizontal bars from the bottom up. Customer says it is also tediously slow. Is this...

Thank you! That will teach me never to purchase second hand trackpads. I just took out a corroded one to replace with a faulty one.

Liquid damage declared but logic board is immaculate. Trackpad circuitboard badly corroded. Trackpad replaced, trackpad flex cable replaced. Some keys dont work, some keys return the wrong character. A replacement A1932 keyboard produces exact same result although an external keyboard works...

If the CPU is dead what displayed the apple logo and increased the time bar? Surely that is driven by the CPU isn't it?

Aren't those ruled out? Ive got the logic board connected to the screen only for the most of this. However the results are the same with trackpad and flex connected. But I will find alternative trackpad and flex if you think so.

Ha! Ive been trying to install Linux on another Mac all week! Ive tried creating a bootable USB stick via a ew different utilities off an ISO and it is never seen when I hold ALT. How can a bootable usb be made? Im using an ISO of opensuse. I dont have a windows distribution but I do have a...

Yes the 1.8ohm to ground is consistent with other boards so that cant explain stopping before end of time bar.

No I couldn't load macOS in safe mode either. I measure 0volts on PVCCGT_S0G_PH1/2/3. Each approx 1.8ohm to ground. pp5v_s0 is 5v ppbus_g3h_cpu is 13v Could this cause my problem or is it only switched on at a late stage?

Immaculate board - no evidence of liquid damage. ppbus_g3h 13v With only screen connected, chimes, apple logo appears, then just before time-bar completes screen goes black and repeat. With only external monitor connected on usb-c same behaviour seen. Alternate SSD tried same result Ive tried...

Keep your pants on - I don't come here very often at all yet I pay every month because I like to support it [but I am not enjoying it right now] . AFAIK we (you and I) have not discussed about PCH's RTC signals. Would it not be appropriate for you to have sent me a link to where they are...

The R5115/6 pads reliably initiate boot with charger attached but not with battery only. PPVRTC_G3H 3.42v when charger attached and same with battery only PPVOUT_S0_PCH_DCPRTC 1.57v when using charger PPVOUT_S0_PCH_DCPRTC 1.3v when using battery only

I managed to find an old genuine battery. Still doesn't boot from battery only. (well occasionally it will) Ive also tried a new keyboard. Perhaps Ive just got a fractured board. The only thing I haven't swapped out is the trackpad.

17/18 3.0 ohms 27/28 20.8 ohms R7121/22 and R7151/52 all look clean, no fractures, not loose

With battery only connected ppbus_g3h 12.8v pp3v42_g3h 3.42v Battery charges up fine. No evidence of liquid damage Tried new keyboard - no change. Boot loops when charger connected and battery disconnected Boots fine with charger and battery connected - new bat on order 5 days away!

Once booted works fine on battery including sleeping but if I shutdown and dont have charger connected it wont boot. Where should I start?