Hi guys I have a Raedon HD 5870 here
It does not power up, in fact it only draws about 100mA from 12V and 3.3V combined..
I can only find 12V and 3.3V on the card, I don't think 5V or anything else is present.
There are three components near the rear of the card marked G78A - can anyone identify these?
They all have 12V on the right hand pin, the centre pin connects to ground, and 0V on the left hand pin. This sounds like they should be fixed output LDOs but it doesn't make sense that all of them are faulty (no output) and it doesn't make sense that the centre pin is short to ground (rather than should be ground) as the graphics card draws almost no power.
Also I have another chip in this area which is a buck controller - the buck coil has no voltage and I can't find a connection from 12V to the controller chip so don't know where it gets it's input power. I also could not find a datasheet - can anyone identify this? V2AF 837
There are also two more ICs in this area, I identified as uP7701U8 which are LDO regulators. Neither have any output or input voltage. One of them takes power from the buck regulator controlled by V2AH 837 - which obviously isn't giving any output as mentioned earlier. (see blue line on attached pic - the uP7701U8 is near to the V2AF buck regulator).
The other uP7710U8 is near the PCIe (below the AMD logo) and also has no input voltage but I can't figure where it should come from - it does not connect to V2AF buck regulator, PCie 12V or EATX_12V, PCIe 3.3V or any of the G78A. However the resistance to ground from the input of this uP7710U8 - and the nearby 0R resistor which is also connected to the input pin, is quite low at 16 ohms.
I couldn't find any open circuit large SMD resistors in this area of the PCB
Maybe someone here knows what voltages should be where? It's like I have something very open circuit somewhere, stopping anything powering up at all, even 5V which should happen automatically if 12V is present.
TIA
Rich
It does not power up, in fact it only draws about 100mA from 12V and 3.3V combined..
I can only find 12V and 3.3V on the card, I don't think 5V or anything else is present.
There are three components near the rear of the card marked G78A - can anyone identify these?
They all have 12V on the right hand pin, the centre pin connects to ground, and 0V on the left hand pin. This sounds like they should be fixed output LDOs but it doesn't make sense that all of them are faulty (no output) and it doesn't make sense that the centre pin is short to ground (rather than should be ground) as the graphics card draws almost no power.
Also I have another chip in this area which is a buck controller - the buck coil has no voltage and I can't find a connection from 12V to the controller chip so don't know where it gets it's input power. I also could not find a datasheet - can anyone identify this? V2AF 837
There are also two more ICs in this area, I identified as uP7701U8 which are LDO regulators. Neither have any output or input voltage. One of them takes power from the buck regulator controlled by V2AH 837 - which obviously isn't giving any output as mentioned earlier. (see blue line on attached pic - the uP7701U8 is near to the V2AF buck regulator).
The other uP7710U8 is near the PCIe (below the AMD logo) and also has no input voltage but I can't figure where it should come from - it does not connect to V2AF buck regulator, PCie 12V or EATX_12V, PCIe 3.3V or any of the G78A. However the resistance to ground from the input of this uP7710U8 - and the nearby 0R resistor which is also connected to the input pin, is quite low at 16 ohms.
I couldn't find any open circuit large SMD resistors in this area of the PCB
Maybe someone here knows what voltages should be where? It's like I have something very open circuit somewhere, stopping anything powering up at all, even 5V which should happen automatically if 12V is present.
TIA
Rich
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