Hi folks,
I wanna start off by saying hi to all you guys as this is my first post, this is the only place I come to when in need of advise and knowledgeable answers. Great forum you all have here. I've been repairing my PC hardware for some time now (Minor cap replacement, Dc jacks). But that's kind of the extent of my knowledge so want to improve my skills and learn a bit more so what better way than to jump right it at the deep end and try fix a dead graphics card ay?
The card in question is a Sapphire 7870 Ghz edition 2GB which I believe sticks to amd's reference pcb design.
The problem is that the PC refused to boot at all when the card is inserted and pcie Molex connectors connected in the case of this particular card 2x 6pin. The Graphics card fans just 'Twitch'.
I've ruled out motherboard and psu. A Tyan K8WE with dual opteron 285's & PC Power & Cooling turbo cool 850w (bought pre Ocz takeover, cost a fortune getting it from the states) love that psu , and I'm pretty sure more than enough power required for this card.
From what I've read around the forums I believe the problem to be a short circuit and the psu's short circuit protection kicks in to prevent further damage.
So I decided to lift off heat sink and take a look at the naked board expecting to find Burnt components maybe a blown capacitor, so I was surprised to see none of these, the board was in very good condition with no sign of damage at all.
Due to a possible short I think we can cancel out caps? Correct me if I'm wrong?
More likely VRM circuitry possible MOSFET at fault, or bad lead free Bga balls? What do you guys think? Thermal paste on the gpu core seemed sufficient and the size of heat sink and copper heat pipes make me think this card didn't overheat but I'm no expert. I've tried enabling chip select on the bios by shorting pin 1-8 I think it was but still nothing, so don't think its a bad flash.
Now I know sapphire have had trouble with this particular model as a result of bad tantalum capacitors on the reverse of the card. I've checked cards serial number / date codes against known bad date range via sapphire website and I'm safe, not one of the 6% of duds.
But from what I've read the symptoms for this are a black screen and not boot-up issues so I've ruled this out. Maybe I could RMA but I'm not the original owner and I've already voided warranty by dismantling. Plus where's the fun in that? I'm not out of pocket so it's not gunna hurt to learn and hopefully help others.
I've tried to sort this myself but am a bit out of my depth and don't know where to start or in which order to test components. I've done the best I can to get a hi res pic of the card and I've sourced data sheets of the mosfets and a few controller ic's.
I have a mastech 8211d pen style multimeter with continuity test buzzer (50ohms according to manual if this makes a difference) and an atlas esr70+ meter and a load of desoldering gear at my disposal.
If someone could point me in the right direction or maybe talk me through what I should do next.
KEY FOR THE IMAGE
RED - 78M05 Voltage regulator
BLUE - CHiL Semiconductor CHL8225 Multi-Phase Buck controller
GREEN - RICHtek 8120 Single-Phase Synchronous Buck PWM Controller
ORANGE - UNKNOWN CHIP AM113? LINEAR IC AMPLIFIER MAYBE?
YELLOW - ON Semi 4904NG Single N-Channel Power Mosfet
LIGHT BLUE - ON Semi 4963NG Single N-Channel Power Mosfet
Im currently mapping out continuity between molex pins on both the 8 pin molex's, will post a pic shortly
I wanna start off by saying hi to all you guys as this is my first post, this is the only place I come to when in need of advise and knowledgeable answers. Great forum you all have here. I've been repairing my PC hardware for some time now (Minor cap replacement, Dc jacks). But that's kind of the extent of my knowledge so want to improve my skills and learn a bit more so what better way than to jump right it at the deep end and try fix a dead graphics card ay?
The card in question is a Sapphire 7870 Ghz edition 2GB which I believe sticks to amd's reference pcb design.
The problem is that the PC refused to boot at all when the card is inserted and pcie Molex connectors connected in the case of this particular card 2x 6pin. The Graphics card fans just 'Twitch'.
I've ruled out motherboard and psu. A Tyan K8WE with dual opteron 285's & PC Power & Cooling turbo cool 850w (bought pre Ocz takeover, cost a fortune getting it from the states) love that psu , and I'm pretty sure more than enough power required for this card.
From what I've read around the forums I believe the problem to be a short circuit and the psu's short circuit protection kicks in to prevent further damage.
So I decided to lift off heat sink and take a look at the naked board expecting to find Burnt components maybe a blown capacitor, so I was surprised to see none of these, the board was in very good condition with no sign of damage at all.
Due to a possible short I think we can cancel out caps? Correct me if I'm wrong?
More likely VRM circuitry possible MOSFET at fault, or bad lead free Bga balls? What do you guys think? Thermal paste on the gpu core seemed sufficient and the size of heat sink and copper heat pipes make me think this card didn't overheat but I'm no expert. I've tried enabling chip select on the bios by shorting pin 1-8 I think it was but still nothing, so don't think its a bad flash.
Now I know sapphire have had trouble with this particular model as a result of bad tantalum capacitors on the reverse of the card. I've checked cards serial number / date codes against known bad date range via sapphire website and I'm safe, not one of the 6% of duds.
But from what I've read the symptoms for this are a black screen and not boot-up issues so I've ruled this out. Maybe I could RMA but I'm not the original owner and I've already voided warranty by dismantling. Plus where's the fun in that? I'm not out of pocket so it's not gunna hurt to learn and hopefully help others.
I've tried to sort this myself but am a bit out of my depth and don't know where to start or in which order to test components. I've done the best I can to get a hi res pic of the card and I've sourced data sheets of the mosfets and a few controller ic's.
I have a mastech 8211d pen style multimeter with continuity test buzzer (50ohms according to manual if this makes a difference) and an atlas esr70+ meter and a load of desoldering gear at my disposal.
If someone could point me in the right direction or maybe talk me through what I should do next.
KEY FOR THE IMAGE
RED - 78M05 Voltage regulator
BLUE - CHiL Semiconductor CHL8225 Multi-Phase Buck controller
GREEN - RICHtek 8120 Single-Phase Synchronous Buck PWM Controller
ORANGE - UNKNOWN CHIP AM113? LINEAR IC AMPLIFIER MAYBE?
YELLOW - ON Semi 4904NG Single N-Channel Power Mosfet
LIGHT BLUE - ON Semi 4963NG Single N-Channel Power Mosfet
Im currently mapping out continuity between molex pins on both the 8 pin molex's, will post a pic shortly
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