I've been trying to repair an RTX 2080 and need some help. The LEDs turn on, but the fans don't spin and the PC doesn't boot with the GPU connected. There is no short to ground.


Resistance - see resistance picture

1 - 25.6 ohm
2 - 0.9 ohms
3 - 14.8 kOhms
4 - 3.12 kOhms
5 - 81.8 kOhms
6 - 10.2 ohms


Voltage - see voltage picture

1 - 12.05 V
2 - 12.05 V
3 - 12.04 V
4 - 0 V
5 - 0 V
6 - 0 V
7 - 4.998 V
8 - 0.025 V
9 - 0 V
10 - 0.019 V

I've struggled to find datasheets for two of the controllers, BFRJ (next to inductor labelled 7 on the pic) and BFDJ (next to inductor 10).

I've been able to deduce that:
i. BFRJ is MP28168GQ
ii. BFDJ is MP8858GQ
- again no actual datasheets have been found.

Controllers voltages are as follows:

BFRJ (inductor 7) - unsure of pinout but I'm hoping you'll be able to make sense of it
1 - 12.05 V
2 - 0 V (ground)
3 - 0 V (ground)
4 - 3.603 V
5 - 0 V (ground)
6 - 0 V (ground)
7 - 0.058 V
8 - 3.314 V
9 - 3.606 V
10 - 0 V (ground)
11 - 0 V (ground)
12 - 0 V
13 - 8.06 V
14 - 4.996 V
15 - 5.002 V
16 - 8.48 V

M8633A (inductor 8)
8 (enable) - 0 v
9 (pgood) - 0.024 v
10, 21 (Vin) - 12.05 V

M8633a (inductor 9)
8 (enable) - 0 v
9 (pgood) - 0 v
10, 21 (Vin) - 12.05 V

BFDJ (inductor 10) - I initially tried to estimate which pin enable, pgood and Vout come from based on a similar datasheet (MP8864) but because MP8864 only has 15 pins I haven't relied on it.

1 - 12.06 V
2 - 0 V (ground)
3 - 0 V (ground)
4 - 0 V
5 - 0.025 V
6 - 0.024 V
7 - 0 V
8 - 0.024 V
9 - 0 V
10 - 0 V (ground)
11 - 0 V (ground)
12 - 0 V
13 - 0.039 V
14 - 0 V
15 - 0 V
16 - 0.029 V

It would seem as though the short/problem exists on/around/after the circuit involving BFRJ/inductor 7 which appears to be a 5 V rail.

A quick check of the Vcc and EN on the 2 MP8633A chips shows they don't have Vcc or EN.

Not sure if this helps or not, but I've been probing around IC MP2888A - the datasheet says it's the multi-phase PWM controller. I thought it might provide a pgood signal to the enable pin on the other ICs on the left hand side but probably not as it controls the VRM phases form what I can gather.

Anyhow, there is no enable or pgood voltage, but VDD18 reads 1.8 V and VDD33 reads 3.3 V - these have nothing to do with enabling the 3.3 and 1.8 V rails do they?

Any help would be appreciated as I'm not sure where to look nect or what the problem might be.

Thanks.