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Seems like this is another one of apple's idiot boards that won't even attempt to start without the battery plugged in.. With a fully charged new battery the system is pulsing on the PM_SLP_Sx_L signals and actually goes into S0 state. CPU doesn't appear to be heating up though but I do have...

Dont have a scope unfortunately, just a fluke meter. If we assume it is pulsing what is next?

SMC_ONOFF_L is triggerin PM_PWRBTN_L yes. There is a tiny pulse on PM_SLP_S4_L - almost missed it with the meter goes up to 0.023v only that I can see then immediately off again.

Little bit of history on this one - customer plugged an external hdd into this one - one of those cheap sata to usb converter box style ones but also plugged in a 5v dc psu to the hdd as well. After which machine is dead - i'm thinking the USB 5V S3 Rail has been back fed with the power from the...

I shall check those thanks! Is there any easy way of testing the PSU's on these or is it a case of if it makes 12V it's probably fine?

After much searching on the board I found it - 820-3478

Got a 27inch Imac in today which has no power. Customer says it was working fine until it was knocked off the table (screen is broken also but that's a separate issue) I've opened it up and appear to have 12V coming out of the PSU to the motherboard and LED1 for standby power is on. When I...

looks like an LCD problem to me

Got an 820-2850 in today - no light on the charger initially - checked board see the ISL6259 has been replaced before so decided to resolder it - after resoldering i'm getting a green light after 15-20 seconds (not instant) and it doesn't go orange. Board starts and says battery is 0% and not...

So i've got an 820-00165 board in at present - was water damaged and repaired backlight circuitry in the past but it's been returned with an issue of running very slow. The system works perfectly when I use an external USB hard drive loaded with Catalina - no slowdowns or freezes at all fans...

Thanks for that good future reference material! Looks fairly similar to the process on the 820-2915 boards. Although I can now mark this case as solved as it appears I was the victim of not checking the whole board very thoroughly under the microscope first. Whilst I did extensively check...

I've not done the mod on this model before do you have any link to instructions for this? I've done plenty of 820-2915 hardware mod to disable GPU before so I do understand the principle. Would bad C9560 originally cause damage to the GPU? First time i'm seeing this problem and i've fixed...

Can confirm doesn't start in SMC bypass mode either - fans go to full for around 5 seconds then it shuts off the same as it does in normal mode

Didn't use hot air no just the iron (Ersa I-con 1 Set to 400C), stays on without the RAM and just beeps then fans ramp up to full speed. Will try SMC bypass mode tomorrow. Also the voltage on C9560 is 1.35v steady not 1.3v as I wrote earlier which from experience is normal. I'm wondering if...

So i've received an 820-2850-A in today with what the customer tells me was kernel panics related to GPU. Knowing this is usually a C9560 issue I have dutifully removed C9560 and replaced it with the bigger 330uf tantalum capacitor as I normally do for these jobs. Now upon testing the board...

Tried Removing U5535 - same behavior also tried routing the CPU sensor into U5535 which also resulted in the same error. At this point I am thinking either SMC issue or something is broken somewhere inside the board. Luckily I have another 820-2879 board which had just a mild case of liquid...

Reflowed and same behaviour assuming bad MCP at this point - given it's working fine otherwise would there be some way of routing some other sensor into U5535 maybe the cpu one? Was thinking if I disconnected pins 2 and 3 of u5535 and routed them to pins 2 and 3 of u5515 I could trick the SMC...

Got an A1278 in today after not seeing any for a while 820-2879 board. History as follows: Came In dead - customer claims tried to change battery to fix macbook - still dead. I open it and find a ton of flux on the bios chip, also notice u3990 has been removed and Q7085 is not soldered on...

With new battery all working perfectly so mark this one as resolved.

PPBUS_G3H Without Battery - 12.61V System will not start with battery connected but if I connect it after turning system on it recognizes it and says 2% not charging. Also PPBUS_G3H Voltage slowly raises from 12.61v up to 13.02V with the battery attached.