I have AMD Vega 56 (GV-RXVEGA56GAMING OC-8GD rev 1.0) that doesn't have signal nor fan spin on system startup.
^ opamp (LM358 SMDR)
^ VBIOS(?) - AH1725 (6?)5041BT E79472
Terminology
PWM = PoWer Management chip
SDA = data line
SCL = clock line
VDDCI = the I/O bus voltage (between memory and GPU core) and comes from the PCI-Express slot. or in other words, more simple: VDDCI = memory controller voltage.
Initial diagnostics
GPU connected to a healthy system results in no fan spin nor display on startup.
Hypothesis
Short to ground preventing the VBIOS boot.
Diagnostics
VDDC is shorted, probing VDDC to 12V in line ground
Cooler
The cooler is fine i connected it to 9V battery and the fans happily spin.
Connecting the GPU without a cooler to a system doesn't give me a display.
Conclusion: The cooler is not causing the short
PCB
I checked all the "bigger components" for conductivity and i couldn't find anything faulty.
Requires more diagnostics for other components, but i don't know what are the expected voltages and the boot sequence (help-wanted)
VBIOS
Pin 8 on VBIOS has 3.36V on power up plugged in PCIe and to PSU 12V2A rail -> VBIOS has power and the main rail is working.
Kreyren
commented
3 years ago
I have AMD Vega 56 (GV-RXVEGA56GAMING OC-8GD rev 1.0) that doesn't have signal nor fan spin on system startup.
Terminology
PWM = PoWer Management chip SDA = data line SCL = clock line VDDCI = the I/O bus voltage (between memory and GPU core) and comes from the PCI-Express slot. or in other words, more simple: VDDCI = memory controller voltage.
Initial diagnostics
GPU connected to a healthy system results in no fan spin nor display on startup.
Hypothesis
Short to ground preventing the VBIOS boot.
Diagnostics
VDDC is shorted, probing VDDC to 12V in line ground
Cooler
The cooler is fine i connected it to 9V battery and the fans happily spin.
Connecting the GPU without a cooler to a system doesn't give me a display.
Conclusion: The cooler is not causing the short
PCB
I checked all the "bigger components" for conductivity and i couldn't find anything faulty.
Requires more diagnostics for other components, but i don't know what are the expected voltages and the boot sequence (help-wanted)
VBIOS
Pin 8 on VBIOS has 3.36V on power up plugged in PCIe and to PSU 12V2A rail -> VBIOS has power and the main rail is working.
PWM (35217-C704P-AV8H)
Seems to be custom-made for this GPU
Probing from 12V in to VDDCI inductor gets me 0.22V
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