Gurmon
Member
Hi,
I have a couple of 27? 2015 IMacs that have pretty much the same issue.
They both came in with 1 light illuminated on the logic board. Usually this can be a short somewhere, but what I found was Q8470 being faulty.
There as a 1V drop across this FET, meaning PM_PGOOD_FET_P12V_S5 was low.
I jumpered across this FET, and the board was fully alive in terms of voltages.
We now have 2 x diagnostic LEDs alive and LE0305 - LE0307 illuminated.
P1V0_S3_PWRGD
CPUVCC_S0_PWRGD
VCCIO_S0_PWRGD
The above are all good
I have all GPU voltages, but the board will not post. No chime.
GFX_OK_L is high & DP_LINK_OK is missing. Which is generated by a GPIO on the GPU, both are required for the third diagnostic LED.
So being out of ideas and not finding anything knock of the board I went into full brain dead mode and started trying different bios files from where ever I could find them i.e. Vinifix?
No change at all. I haven?t really come across too many slimline macs with dying/dead GPUs. And so far, none on the 2015 AMD R395X.
I haven?t roasted this GPU to see if it will come back to life as of yet?no point since I can?t find replacement GPUs for this model.
Any ideas, I?m still thinking vBIOS, so if anyone has a known good bios file, I would appreciate any insight.
I have attached the original bios, if anyone would care to have a look.
https://drive.google.com/file/d/1fPJUfe9Vec0wiFWBAsXj0hp_-FHXiAJ9/view?usp=sharing
Thanks in advance
I have a couple of 27? 2015 IMacs that have pretty much the same issue.
They both came in with 1 light illuminated on the logic board. Usually this can be a short somewhere, but what I found was Q8470 being faulty.
There as a 1V drop across this FET, meaning PM_PGOOD_FET_P12V_S5 was low.
I jumpered across this FET, and the board was fully alive in terms of voltages.
We now have 2 x diagnostic LEDs alive and LE0305 - LE0307 illuminated.
P1V0_S3_PWRGD
CPUVCC_S0_PWRGD
VCCIO_S0_PWRGD
The above are all good
I have all GPU voltages, but the board will not post. No chime.
GFX_OK_L is high & DP_LINK_OK is missing. Which is generated by a GPIO on the GPU, both are required for the third diagnostic LED.
So being out of ideas and not finding anything knock of the board I went into full brain dead mode and started trying different bios files from where ever I could find them i.e. Vinifix?
No change at all. I haven?t really come across too many slimline macs with dying/dead GPUs. And so far, none on the 2015 AMD R395X.
I haven?t roasted this GPU to see if it will come back to life as of yet?no point since I can?t find replacement GPUs for this model.
Any ideas, I?m still thinking vBIOS, so if anyone has a known good bios file, I would appreciate any insight.
I have attached the original bios, if anyone would care to have a look.
https://drive.google.com/file/d/1fPJUfe9Vec0wiFWBAsXj0hp_-FHXiAJ9/view?usp=sharing
Thanks in advance
