Clean (dusty) board, no liquid damage
Orange light on charger
Intermittent (rare) fan spin

2: 14.61
3: 3.97
12: 5.07
20: 5.03

17: 8.59
18: 8.59
17-18: 3.3 O

28: 14.38
27-28: 20 O

14: 3.39

PPBUS_G3H: 8.59
PP5V5: 5.13
PP5V_S4RS3: 5.137
PP5V_S0: 5.13
PP3V3_S4: .03
PP3V3_SUS: 3.35
PP3V3_S3: 0
PP3V3_S0: 0



Staff member
"PPBUS_G3H: 8.59 "
Don't waste more time with measurments around U7100!

"PP3V3_S4: .03 "
Are you sure?
Check it for short and inspect U8000...



3V3_S4_FET_R: 0.75V-2.5V <----- Should be 3.3V but dips as low as 0.75 V, wait 5 minutes, 2.5V, then 0.75V again.
PP3V3_S5: 3.36V

But my reading earlier was not incorrect.
I measured it multiple times and PP3V3_S4/3V3_S4_FET_R was 0 V
Now it is not. I can't explain it.
No fan spin.
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Staff member
Do not replace, it is good.
I was thinking 3V3_S4 is steady 0V; you didn't specify any fluctuation.
Be aware when you post in the future.
You are first interested to provide correct info...

So post all the voltages you get when fan spins.
How much time (seconds maybe) have them on?


It was a steady 0V.
Now its 0.75V, 5 minutes ago its was 2.5V
When the fan starts spinning, I get a 3.36V.

I am going to leave the board plugged in and see what happens.
Sorry for the confusion.
I honestly have no idea why it does that.

I unplugged the charger from the wall, replugged it in.
Now the machine starts and boots to a folder with a questionmark.
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I decided to swap out the dc in board and the flex cable because of all the weird charger behavior,

The machine will now boot to the OS with an external drive but the cpu heat pipe is super hot (i mean burn your finger hot).
20 seconds after booting the CPU must get too hot because the machine starts to get a spinning ball and becomes unresponsive.

All the while the fan is now going very fast at all.


how would the heatpipe/CPU heatsink be broken? Just asking for my own understanding.
Wouldn't that be clearly visible like a crack etc?

Any chance this is the BIOS?


Staff member
CPU cannot get very hot so fast, in normal condition.
Very small crack on the pipe and loses all the liquid, or gas, whatever has inside.
You can try clean ME BIOS too...


OK heatpipe replaced
I thought it fixed it

CPU temps 48-60, idle
Plugged in charger and battery.
SSD in place. I was planning on installing a fresh copy of Catalina.
Green light on charger, then orange which is good.

Then 3 minutes later, charger light goes out. If I plug in and unplug the AC adapter from the wall the charge light comes on again, then goes out after 3-4 minutes.
CPU starts to heat up, did not measure temp but it is burning hot.
Fan still appears to be medium speed.

FYI, the machine boots to the desktop OS fine off of an external USB drive.

So I see 2 problems:

1) charger light goes off so I am losing PP4V42 or SMC_BC_ACOK for whatever reason.

I measured U7100 voltages above but I guess I should measure it when this charger light goes out.

2) the CPU is still super hot
3) ? CPU temp sensor

BIOS issue?


Staff member
Temp sensor cannot overheat the CPU, if fan already goes up.
Did you try clean ME BIOS?

Check if Magsafe light is stable, without battery connected.


OK just got my hands on a Medusa 2.
This thing took exactly 1 month to get here from Germany with the current environment.

I have hooked it up.

No chip found (H)

This is a 820-00165 with a WINBOND chip so I think I have to Set the QE bit in case of a Winbond ROM chip
per the website.

I would RTFM but there is no FM.

I have emailed the support for the manual.

In any case I am using the A4160 adapter that (red) came with the Medusa 2
I am fairly sure I have to set up ? dip switches per the website to work win a Winbond chip.

By the way this 820-00165 boots al the way into the OS.
Its the fan that never stops spinning at max.
Temps are fine in HW monitor (see above)
DC in board swapped.


Staff member
Be sure to connect Medusa adapter correctly; the arrow must points to backside of the laptop.
Do you get blue light on it, at least?
Also be sure to use the proper Medusa port; the one near dip switches.

In order to detect SPI chip correctly on this board, you must plug in the adapter after Magsafe is connected.
To avoid any headache, I inject 3V into 3V3_SUS rail and no need to connect Magsafe anymore; all the job is done with board in off state.

Possible no ME region issue, if macOS works fine.
But is worth to try.


OK that was stupid.
I had it plugged in facing front.

OK it reads it now.
I can watch the videos on the CMI Zapper website.

I think I need to read and store a backup into the Medusa first.
Do you have the list of what the dip switches do.
Again...I am waiting for the manual to be emailed to me.

I hope this works beacause I have swapped everything out on this board:

DC in Board

Works great boots into Catalina
Temps are fine.

Fan is going full speed though.
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Me region cleaned using medusa
now mac gets to apple logo, stuck at like about 5%, never gets to OS
cpu immediately heats up, super hot

is this a mosfet issue
CPU heating up within 15 -30 seconds


OK reflashed from MEDUSA backup and then reset NVRAM.
Seem to now boot into OS

Weird but on boot it looks like it is still installing the OS
Says "10 minutes remaining" and then booted into OS.
Not sure if that is due to the reflash.

I can reclean the ME region again with the Medusa.

The CPU is running very hot (ie I can burn myself on the heatpipe)
The heatpipe is new
Fan is going relatively slow.

i installed hwmonitor:
CPU: 67c idle
FAN: 1200-1400RPM

In HW Monitor

I am actually working on another machine (which you helped me with as well) where similar readings are happening but on that machine the fan is at 6300 and CPU is 43C.

On this machine:
Fan is at 1300 and CPU is 67C, so the exact opposite.
Battery Temp Sensor: 129 with battery not connected

I hate these battery sensor issues.
There is no clear sensor to change etc.
They work on trackpad sensor I think.

Should I reclean the ME again?
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Staff member
Battery temp sensor is placed on trackpad board.
So try known good trackpad, even its flex is worth to test.

Recover your data and do fresh macOS intall.