MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

[Gigabit2]

I have a MacBook Pro Mid 2012 with 820-3330-B board.

The laptop shows a green light on the charger, turns on and the fans spin for about five seconds. Then it turns off and this repeats over and over.

Before it turns off, the SuperDrive (DVD/CD drive) makes a noise like it does when it first turns on from cold (on a working machine).

I am stumped, can anyone help?

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

This typically points to a bios fault. You need to reflash the bios.

Similar but for another logic board:

https://www.logi.wiki/index.php/820-00165_Pulsing

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi again mon2,

Can you help me with reflashing?

[CleanME]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi mate, I will also add that you ideally need bios dump with clean ME region otherwise your machine may not work very well. You need to find a file on the forum with clean ME and then reflash the IC with programmer.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi, I not done flashing before. Where am I flashing, what is the device I need?

[ugamazing]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

For diagnosis purposes, you can usually just swap another SPI ROM chip to the board *to see if board chimes*. You still need to clean ME, but you can at least rule out a dead/bad chip or corrupted dump on your current chip/board.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

The bios is actually on your board already but it needs to be removed -> backed up (for safety) -> erased -> reflashed with clean code.

That is not my comfort zone on cleaning up the bios code so wait on comments from others. Otherwise, you will need a flash programmer -> small PCB to allow you to program the actual device itself.

Do you have a flash programmer at this time ? If not, should be possible to buy through Amazon and a local reseller in your region. But best to do some homework so that the programmer can be used for other cases in the future.

The bios to review is @ U6100.

Before we jump to reflashing, can you do the following ?

Meter in DC volts scale (5 volts or higher is ok).

Carefully check the voltage to ground of each pin on the U6100 BIOS. We want to be sure that the power rails are ok; the signal rails are actually reaching the BIOS chip.

This is an 8 pin SOIC package so should be ok to probe with care while the unit is powered.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Does it have to be SPI from exactly the same model or can it be a 2011? I have one of these around.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

The contents are important but so is the density and operating voltage of the component.

There are resellers on Ebay that offer pre-programmed devices but the experience may be worth the effort.

Can you check if the voltages are ok on this device ? Any liquid damage ? Perhaps some line / PCB trace on the flash is broken that can lead to this event.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi mon2,

Pin 1: 3.32V
Pin 2: 3.28V
Pin 3: 3.32V
Pin 4: GND
Pin 5: 0.00V
Pin 6: 0.00V
Pin 7: 3.02V
Pin 8: 3.32V

No liquid damage, machine looks very clean.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Confirm that the series resistors are present and not damaged.

You can measure the resistance from one side to the other - no power during resistance measurements.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

R5110: 0.02
R5120: 0.06
R5111: 0.02
R5121: 0.06
R5112: 0.03
R5122: 0.06
R5123: 3.28

All measured on 20k mode

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi mon2,

Is this ok? I ordered new chip

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

R5123: 3.28

this one does not look correct. Can you check it again ?

it should be ~0.02 if using 20k scale.

Better is you use the lowest ohms scale so that we can read as ~15 ohms.

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Hi mon2,

My apologies, board is 820-2915-B!

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

R5123 measuring 14.8 on 200 mode @mon2.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

~15 ohms is ok.

Confirm the voltage on the attached power rails.

Do they match the values in the schematic?

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

C2492 is missing but at pin 1 is showing 1.04V.

C2494 is missing, showing 0.95V when fan spinning, 0.2V when fan not spinning

[Gigabit2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

After re-test, C2494 is missing but at pin 1 showing 1.04V.

[mon2]

Re: MacBook Pro Mid 2012 turns on, fans spin for five seconds and turns off, repeats

Both caps are marked as NO STUFF so that is ok. Another tech on Logiwiki referenced that this caused the same fault as yours because he had a broken resistor @ R2491.

What is the voltage of ALL_SYS_PWRGD ?

This signal rail is the 'digital OR'ing' of multiple open-drain outputs and is with a local pull-up resistor. See sheet 72 of the schematic.

If any rail is BAD or not within spec, then the power good detector for that rail will pull DOWN this common power good status pin.

That is, ALL power rail power good signals should be high impedance (hi-z) so that the local pull-up @ R7967 can pull-up this common signal status.

Respectively, if you see ~3v here - then all power rails being monitored are GOOD. Hence the name.

What is the voltage on this ALL_SYS_PWRGD ?