820-3476-a Power no display

[2informaticos]

60/85W Magsafe 2 charger for sure?

 

[Anterweb]

Oh ffs, what a noob I am !
Plugged in an 85w mag and of course the fan starts to spin, also just noticed while trying this again back in the mac adding one cable at a time that no matter what is connected and regardless of running on magsafe or battery when you turn it off by holding the power button after a couple of seconds it seems to power itself on again and the fan starts spinning and keeps spinning until I hold the power button down and disconnect the battery and the magsafe.

 

[Anterweb]

Also just tried to boot in smc bypass, I get full fan spin but still no display on external or internal screen.

 

[2informaticos]

Do all mentioned checkings...

 

[2informaticos]

Don't you get 3V at pin 2/U1950?

Remove U1950 and check its pads and board traces.

 

[Anterweb]

OK removed U1950 noticed that C1950 looked slightly corroded and it looked like a break in the trace , Removed C1950 and made sure I had repaired the trace getting 3v to pin 8,

I got 3V at pin 2/U1950 now,

But... I have blown U3560 into the abyss! ( How important is this? ) can I work without it or is this another board for parts bin?

 

[2informaticos]

It should work without it.
You probably don't need AP, or PCIE wake function.
You can place R3560, for AP wake...

 

[Anterweb]

Ahh, That's cool! But even after getting correct voltages on U1950 I'm still getting fan spin, cpu gets warm but no beep no display,

It's yet another one I feel that has beaten me

 

[2informaticos]

Do you get 3V at pin 3/U1950?
Also check CPU coils and PLT_RESET_L.

 

[Anterweb]

"Do you get 3V at pin 3/U1950?" = yes

CPU Coils both at 1.7v

PLT_RESET_L = 0v

I also just noticed that since cleaning up U1950 I no longer get a constant fan spin but what seems to be power cycling , on for a few seconds then off for a few then back on again etc etc same for both voltages and fan spins .

 

[2informaticos]

Check CPU_VCCST_PWRGD and CPU_VR_READY.
Also check presence for all voltages on page 11.

There are many power rails to check on pages 59 & 60 too.

Just in case, try turning on in SMC bypass mode.

 

[Anterweb]

CPU_VCCST_PWRGD = 1.047v
CPU_VR_READY = 1.052v
Page 11 , 59 & 60 all voltages present ( that took cooking ages! )

SMC Bypass samer shit,

I can't see any reason this shouldn't power up and play, But fan spin and cpu getting warm is all we get.

 

[2informaticos]

Is the board power cycling now?

Try known good BIOS...

 

[Anterweb]

Power cycling seems to have stopped or only happens after long periods of being turned on when testing voltages,


I'm currently in the process of ordering a Medusa ( And a pile of Tiresias (the GPUkiller) chips ) from Harald but he is currently on vacation until the 23rd of june

Without a Medusa would I need to remove the bios chip to try good bios? Or am I best of waiting till the Medusa arrives?

( Also I notice there are 3 different versions of the Medusa what version would you recommend I get?

 

[Anterweb]

Spoken to Harald, I have to wait until he is back from vacation ( 23rd) before I can put an order in so going to try removing bios chip and using my cheap programmer.

I've just tyred searching the board for a clean ME bios for this board but don't see one posted recently. Would you have a good bios file I could try please?

Also could you give us your feedback on the battery port tester when you have had a chance to try it out.

 

[2informaticos]

820-3476-Working-CleanME.bin

drive.google.com

Try this file as is, don't change serial number.
If works, then change serial and fix checksum.

 

[Anterweb]

Managed to get back to this one today.

Tried your bios and same shit sadly,

Powers on, cpu gets warm no display on internal or external display.

 

[2informaticos]

PLT_RESET_L still low?