820-00165 fan spin but no boot

gevans91

New member
Got a 820-00165 has green light, fan spins for 10 seconds, goes off, comes back on and ramps up to full speed. No chime present

All rails seem to be present, no water damage to board and no corrosion as far as I can see.

Only odd thing I can see is Q3080* looks burned?

PPBUS_G3H is sitting at 8.59v
 

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2informaticos

Administrator
Staff member
Yes, there will not be thunderbolt support anymore.
If board works, then we see later if you want to get thunderbolt working too.
 

gevans91

New member
The rails all seem to be the same without it attached to board

PPBUS_G3H - 8.59v
PP3V42_G3H - 3.417v
PM_SLP_S4_L - 3.325v
ALL_SYS_PWRGD - 3.323v
PP3V3_SUS - 3.327v
PP5V_S0 - 5.10v
 

2informaticos

Administrator
Staff member
You didn't mention other voltage than PPBUS_G3H before!
We are not sure if "All rails seem to be present" means all voltages are correct.

Do you get 3V at pin 3/U1950 and PLT_RESET_L?
 

gevans91

New member
Sorry should have listed all the voltages at the start

Yeah i've got 3.418v on pin 3 U1950

and 3.327v on PLT_RESET_L
 

2informaticos

Administrator
Staff member
Did you test for USB activity?

Check all SPI Bus Series Termination resistors and their traces.
If all good, try new BIOS.
 

gevans91

New member
Tested all the termination resistors and the traces, all appear to be good

Where would be best to source a new bios? I don't have a donor board to get one off, am I better buying a pre-programmed one or are programmers worth investing in?
 

2informaticos

Administrator
Staff member
Some links should be already posted on the forum, for clean BIOS files.
If you plan to stay in business with Apple boards, get Medusa programmer.

Any other cheap USB programmer can work, but will need to remove/resolder BIOS chip.
 

gevans91

New member
replaced the bios chip, still no sign of booting, I still get fan spin but it no longer ramps up to 100% like it was doing before, voltages are all still the same as before
 

gevans91

New member
Looks like your right, done some more testing tonight, tested all the inputs to the CPU, all measuring fine but still no post

Weird thing is I get usb activity, should you still get usb power if CPU is dead?
 

2informaticos

Administrator
Staff member
USB power and activity is not the same thing!
Do you get steady light on USB mouse if you disconnect/reconnect it when board is turned on?
Still better to test using bootable pendrive with Link LED; if flashes, there is 100% USB activity.
 

gevans91

New member
Turns out there is usb activity. Tried 2 different mouse's on it and they both light up

Still a chance the cpu is dead or is that a good sign there's still life?
 

2informaticos

Administrator
Staff member
CPU should be OK, if you confirm USB activity.
I still recommend you to test with macOS pendrive with Link LED; if flashes, is confirmed 100%.

Try PRAM reset.
 

gevans91

New member
Probably gonna sound like a stupid question but should there be anything on the usb or does it not make a difference?

It lights up for a brief second when I power on and then goes off. Tried pram reset and no difference

Also not sure if it makes a difference but the original bios chip was a mxic branded chip but the replacement I got was a winbond. Was definitely for the correct Mac though
 

2informaticos

Administrator
Staff member
So you do NOT have USB activity, as I imagined.
I already told you, do not confuse USB power with activity.
CPU issue probably...
 
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