[Solved] RX 460 Blown Fuse

RazorWind

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Removing low side mosfet didn't helped. Caps are still shorted to ground.
Do you have continuity between the 12V input fuse (which I think you said is open) and the source pad on the low side mosfet you removed?

If yes, then your short is probably in the board itself. You can do the "what gets hot" test I told the OP to do, but I'd bet good money that what you'll find is that nothing except maybe the core gets warm, and if that's the case, this card is beyond saving.

Edit: Also, check, the removed components for resistance between their terminals, and make sure you actually have a short in the component, and not the part of the board they were connected to.
 
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kodaf56

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Do you have continuity between the 12V input fuse (which I think you said is open) and the source pad on the low side mosfet you removed?

If yes, then your short is probably in the board itself. You can do the "what gets hot" test I told the OP to do, but I'd bet good money that what you'll find is that nothing except maybe the core gets warm, and if that's the case, this card is beyond saving.

Edit: Also, check, the removed components for resistance between their terminals, and make sure you actually have a short in the component, and not the part of the board they were connected to.
I checked capacitors on other similar working card and they behave the same as on my broken card, so that's not the issue and there's no short on the board. But I think I found a problem, I didn't see that before but I lost a tiny resistor and a capacitor close to the mosfet when I was swapping it. This might have killed a new one. I managed to find the resistor and I soldered it back (it was really difficult) but the cap is gone. Can lack of this little SMD cap kill the mosfet again?

CAP.png
 

RazorWind

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I checked capacitors on other similar working card and they behave the same as on my broken card, so that's not the issue and there's no short on the board. But I think I found a problem, I didn't see that before but I lost a tiny resistor and a capacitor close to the mosfet when I was swapping it. This might have killed a new one. I managed to find the resistor and I soldered it back (it was really difficult) but the cap is gone. Can lack of this little SMD cap kill the mosfet again?

View attachment 228611
It absolutely could. It's hard to say without having the card in my hands to see what those pads are connected to. In a lot of cases, the caps are used for noise suppression, where the loss of one won't hurt anything, but not universally. They can be used for other things, such as the bootstrap circuit. The easy way to determine if this is your problem is to remove the corresponding one from another phase, measure its capacitance, and then solder the one you removed back on, along with a new one in place of the missing one.

The hard way is to figure out what those pads connect to and use one's understanding of the circuit to decide if it's critical or not. Chances are, it is.
 

Kzoak

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Short answer is probably not, for a couple of reasons.

First, many of the GCN designs have a voltage controller that is smart enough to tell that one phase isn't running at all. Exactly what it does when this happens, I don't know, but there's a decent chance that it will just not work at all. At best, it's problematic.

Second, with only four phases, you're down 25% of your power supply to the core. If you don't do a lot of compute heavy tasks with this card, you may get away with it, but it sort of defeats the purpose of having a powerful GPU if you can't use it, and you can obviously forget about overclocking.
Because I've seen it in the videos I had to try it myself. I checked all of the MOSFETs and found one that behaved differently. All of them had almost the same values except for this one, that turned out to be the same as kodaf56 's.

I desoldered it. Plugged in my "power supply" and the core couldn't get warm. Also it cleared the Fuse -> GND short.

IMG_20200309_102216.jpg IMG_20200309_103940.jpg IMG_20200309_132348.jpg

I assembled everything back and put it into the main PCIe slot. It gave me a sign of life - fan spin! Then the screen was still black... but the system turned on. I turned off the PC and put the card into the second PCIe slot and connected the display into the working card. System didn't detect the card. But fan spin was still there and MOSFETs were getting hot.
I cleared CMOS as I had Fast Boot turned on, so I turned it off and booted into the system with BIOS defaults.
The card has been detected, but not as the RX 460.

gpu_test1.png


Downloaded the newest drivers. Installed them (clean install). Reboot. After that I plugged the display into the RX 460 and Windows' plug-in sound has blessed my ears. Monitor turned on displaying the picture!
Turn off. Put RX460 into the main PCIe slot. Get rid of the old thing and now I'm here :) I've underclocked it a lot just in case. I didn't stress test it yet or anything. But I'm pretty sure it will work with my throttled settings.

Thank you RazorWind for your great help!
What a journey! :) I've learned so much about GPUs, VRMs and everything related to it. Now I'll need to wait for new replacement to come, but as you can see, the GPU can work without a MOSFET (for who knows how long, but I'll assume, for long enough for the replacement to come).

works.png
 
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RazorWind

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Because I've seen it in the videos I had to try it myself. I checked all of the MOSFETs and found one that behaved differently. All of them had almost the same values except for this one, that turned out to be the same as kodaf56 's.

I desoldered it. Plugged in my "power supply" and the core couldn't get warm. Also it cleared the Fuse -> GND short.

View attachment 228706View attachment 228707View attachment 228708

I assembled everything back and put it into the main PCIe slot. It gave me a sign of life - fan spin! Then the screen was still black... but the system turned on. I turned off the PC and put the card into the second PCIe slot and connected the display into the working card. System didn't detect the card. But fan spin was still there and MOSFETs were getting hot.
I cleared CMOS as I had Fast Boot turned on, so I turned it off and booted into the system with BIOS defaults.
The card has been detected, but not as the RX 460.

View attachment 228703

Downloaded the newest drivers. Installed them (clean install). Reboot. After that I plugged the display into the RX 460 and Windows' plug-in sound has blessed my ears. Monitor turned on displaying the picture!
Turn off. Put RX460 into the main PCIe slot. Get rid of the old thing and now I'm here :) I've underclocked it a lot just in case. I didn't stress test it yet or anything. But I'm pretty sure it will work with my throttled settings.

Thank you RazorWind for your great help!
What a journey! :) I've learned so much about GPUs, VRMs and everything related to it. Now I'll need to wait for new replacement to come, but as you can see, the GPU can work without a MOSFET (for who knows how long, but I'll assume, for long enough for the replacement to come).

View attachment 228709
Daaaaaang you got lucky. It's almost never JUST a MOSFET.

It being the case that the short was cleared by removing just that one MOSFET, you could probably actually fix the card properly if you just bought a new one and soldered it on there. You would probably want to check the gate pin duty cycles on each phase to make sure you don't have a bootstrap circuit that's not working (particularly on this phase), though.
 
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Kzoak

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Daaaaaang you got lucky. It's almost never JUST a MOSFET.

It being the case that the short was cleared by removing just that one MOSFET, you could probably actually fix the card properly if you just bought a new one and soldered it on there. You would probably want to check the gate pin duty cycles on each phase to make sure you don't have a bootstrap circuit that's not working (particularly on this phase), though.
Replacement is coming ;)
It sounds like I would need an oscilloscope to check this though. But if I'll solder a new MOSFET it's not like it does matter right now. But yeah, I'll buy an oscilloscope in the future for sure. Another toy to have fun with :)
 

RazorWind

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Replacement is coming ;)
It sounds like I would need an oscilloscope to check this though. But if I'll solder a new MOSFET it's not like it does matter right now. But yeah, I'll buy an oscilloscope in the future for sure. Another toy to have fun with :)
If you have a multimeter that measures frequency (mine does) you don't need a o-scope.
 

kodaf56

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Because I've seen it in the videos I had to try it myself. I checked all of the MOSFETs and found one that behaved differently. All of them had almost the same values except for this one, that turned out to be the same as kodaf56 's.

I desoldered it. Plugged in my "power supply" and the core couldn't get warm. Also it cleared the Fuse -> GND short.

View attachment 228706View attachment 228707View attachment 228708

I assembled everything back and put it into the main PCIe slot. It gave me a sign of life - fan spin! Then the screen was still black... but the system turned on. I turned off the PC and put the card into the second PCIe slot and connected the display into the working card. System didn't detect the card. But fan spin was still there and MOSFETs were getting hot.
I cleared CMOS as I had Fast Boot turned on, so I turned it off and booted into the system with BIOS defaults.
The card has been detected, but not as the RX 460.

View attachment 228703

Downloaded the newest drivers. Installed them (clean install). Reboot. After that I plugged the display into the RX 460 and Windows' plug-in sound has blessed my ears. Monitor turned on displaying the picture!
Turn off. Put RX460 into the main PCIe slot. Get rid of the old thing and now I'm here :) I've underclocked it a lot just in case. I didn't stress test it yet or anything. But I'm pretty sure it will work with my throttled settings.

Thank you RazorWind for your great help!
What a journey! :) I've learned so much about GPUs, VRMs and everything related to it. Now I'll need to wait for new replacement to come, but as you can see, the GPU can work without a MOSFET (for who knows how long, but I'll assume, for long enough for the replacement to come).

View attachment 228709
Nice! It's weird that the same mosfet was faulty. I think there's something more to it, but I don't know where to look for a problem as the only thing that I could find is a broken mosfet and the rest seems alright. I hope your card won't die again as mine did after a few days.
 

Kzoak

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If you have a multimeter that measures frequency (mine does) you don't need a o-scope.
Unfortunately mine doesn't. But it's not an issue. I'll just solder new MOSFET in there.

Nice! It's weird that the same mosfet was faulty. I think there's something more to it, but I don't know where to look for a problem as the only thing that I could find is a broken mosfet and the rest seems alright. I hope your card won't die again as mine did after a few days.
I'm pretty sure my card died because of the drivers fault what made it "reinitialize" (for the Nth time). And I'm used to that 99% of electronics is dying during its startup. Looking at Gigabyte's PCB I can only assume why this MOSFET fails. because there are so many missing components that I wonder why would they waste their time to design it this way :) I would blame something responsible for the startup (already mentioned bootstrap circuit?).
 

Kzoak

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I just noticed something very strange.
My fan settings are ignored. They worked yesterday (while I was setting them) but now the fans are spinning and they stop... spin again for a while and stop again. Maybe the whole core of the problem is in the fan (or software controlling the fan).
fanspeed.png ignoredsettings.png
I have ~45°C right now and the fan should keep spinning but it doesn't.
 

kodaf56

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I just noticed something very strange.
My fan settings are ignored. They worked yesterday (while I was setting them) but now the fans are spinning and they stop... spin again for a while and stop again. Maybe the whole core of the problem is in the fan (or software controlling the fan).
View attachment 228990View attachment 228991
I have ~45°C right now and the fan should keep spinning but it doesn't.
Something similar happened to me before it died. One fan is probably dead now - at least mine was. I thought they are broken because of the initial failure of the card and the card is fine but If that happened to you too I think that there's still a problem on the board even after removing the short. Check them separately to see if they work. They're connected together inside plastic shroud that you can open by removing 2 screws at the top and at the bottom of the cooler. If one of the fans will be dead then I would recommend you to stop using the card as it will probably die soon as mine did.
 

Kzoak

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Something similar happened to me before it died. One fan is probably dead now - at least mine was. I thought they are broken because of the initial failure of the card and the card is fine but If that happened to you too I think that there's still a problem on the board even after removing the short. Check them separately to see if they work. They're connected together inside plastic shroud that you can open by removing 2 screws at the top and at the bottom of the cooler. If one of the fans will be dead then I would recommend you to stop using the card as it will probably die soon as mine did.
Well the fans are working great after the reboot and are now following my fan speed settings. It seems that there's something wrong with the driver. It worked good yesterday. I plugged in second monitor today (and I didn't reboot the system after that). Do you have double monitor setup? I remember AMD drivers have had lots of problems handling more than one monitor. Maybe it's still present.
 

kodaf56

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Well the fans are working great after the reboot and are now following my fan speed settings. It seems that there's something wrong with the driver. It worked good yesterday. I plugged in second monitor today (and I didn't reboot the system after that). Do you have double monitor setup? I remember AMD drivers have had lots of problems handling more than one monitor. Maybe it's still present.
I have RX 570 in my other PC and I sometimes use dual monitors. Everything is working with the latest AMD driver.
 

RazorWind

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I'm pretty sure my card died because of the drivers fault what made it "reinitialize" (for the Nth time). And I'm used to that 99% of electronics is dying during its startup. Looking at Gigabyte's PCB I can only assume why this MOSFET fails. because there are so many missing components that I wonder why would they waste their time to design it this way :) I would blame something responsible for the startup (already mentioned bootstrap circuit?).
MOSFETs fail due to heat. Does it have a heatsink on it when the card is properly assembled?
 

kodaf56

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I soldered that little missing capacitor on my card but in the process resistor that I soldered back before "peeled off" from the PCB with one of the solder pads. I think I can fix that with little cables but I don't know where it's connected. Do you guys have any tips for finding what it's connected to? I measured it's resistance and it has around 125K ohms. One of the pads for that resistor is connected to ground.
 

RazorWind

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I soldered that little missing capacitor on my card but in the process resistor that I soldered back before "peeled off" from the PCB with one of the solder pads. I think I can fix that with little cables but I don't know where it's connected. Do you guys have any tips for finding what it's connected to? I measured it's resistance and it has around 125K ohms. One of the pads for that resistor is connected to ground.
Is there anything left of the trace that went to it that you can get a multimeter probe on?

Also, are you using a soldering iron or hot air? You really need to use hot air on those tiny SMD components - it's SO much easier than trying to get the components to stay in place while heating them with an iron.
 

kodaf56

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Is there anything left of the trace that went to it that you can get a multimeter probe on?

Also, are you using a soldering iron or hot air? You really need to use hot air on those tiny SMD components - it's SO much easier than trying to get the components to stay in place while heating them with an iron.
There is something and I can probe that. I'm using hot air, but I tried soldering it with the iron first and that's probably why that pad peeled off later in the process of soldering that capacitor with hot air.
 

RazorWind

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There is something and I can probe that. I'm using hot air, but I tried soldering it with the iron first and that's probably why that pad peeled off later in the process of soldering that capacitor with hot air.
Honestly, the best way to figure it out is to test for continuity nearby with your multimeter in continuity mode. Put one probe on the trace, and drag the other over the pins on nearby ICs until you get a tone.
 

kodaf56

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Honestly, the best way to figure it out is to test for continuity nearby with your multimeter in continuity mode. Put one probe on the trace, and drag the other over the pins on nearby ICs until you get a tone.
Nothing beeps, my multimeter in continuity mode shows 1966 from broken pad to ground, also 1966 from pad to drain of the mosfet nearby and 1967 from pad to source pin on the mosfet. There's no connection between gate pin and broken pad. Another interesting thing is that from the gate pin to ground all the other mosfets have around 8k ohms but on that mosfet without the resistor there is 10k ohms.
 
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kodaf56

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I think I won't be able to find where that pad should be connected so I decided to solder a similar resistor on cables to the trace itself, but it's not holding well so I think I will need to glue the cable. What glue do you recommend for such a purpose?
 

RazorWind

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I think I won't be able to find where that pad should be connected so I decided to solder a similar resistor on cables to the trace itself, but it's not holding well so I think I will need to glue the cable. What glue do you recommend for such a purpose?
You can't just glue the wire on there. It needs to be soldered. Once it's soldered at both ends, theres something called conformal coating, which is sort of like clear nail polish, that you can use to hold it down. Super glue would work, too.
 

Kzoak

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Because of the worldwide spread virus it took a very long time before the package with the new mosfets came.

I was testing how the card behaves without the mosfet. I downclocked it so it doesn't exceed 808 MHz and it topped at ~30 W usually at ~22 W under the load. I "torture tested" it for 72 h straight but because these were real world calculations they weren't using 100% but ~90% of the card's potential. Anyway the card handles it without a problem.

Let's get back to the new mosfet. I soldered it into the place. I upped the clock to 1100 MHz so it means it is still 100 MHz below the stock.
IMG_20200330_182818.jpg
After 10 minutes of "torture test" the fuse has blown and the same mosfet is shorted. I desoldered it again leaving the core with 3 phases, replaced the fuse and the card works as it did previously.
I don't know what to think about it as I have no idea what can cause killing the mosfet this fast. From what I've learned about VRMs, the high side mosfet can die because of some high voltage spike, but usually it's the temperature that kills it. The only thing I can think of that could cause it to burn is the controller telling it to work for e.g. twice as long than it should.
 

RazorWind

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Because of the worldwide spread virus it took a very long time before the package with the new mosfets came.

I was testing how the card behaves without the mosfet. I downclocked it so it doesn't exceed 808 MHz and it topped at ~30 W usually at ~22 W under the load. I "torture tested" it for 72 h straight but because these were real world calculations they weren't using 100% but ~90% of the card's potential. Anyway the card handles it without a problem.

Let's get back to the new mosfet. I soldered it into the place. I upped the clock to 1100 MHz so it means it is still 100 MHz below the stock.
View attachment 234408
After 10 minutes of "torture test" the fuse has blown and the same mosfet is shorted. I desoldered it again leaving the core with 3 phases, replaced the fuse and the card works as it did previously.
I don't know what to think about it as I have no idea what can cause killing the mosfet this fast. From what I've learned about VRMs, the high side mosfet can die because of some high voltage spike, but usually it's the temperature that kills it. The only thing I can think of that could cause it to burn is the controller telling it to work for e.g. twice as long than it should.
<cough> bootstrap circuit</cough>
 

GabboDoc

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Hi everyone,
I'm new to the forum as I discovered it just yesterday while troubleshooting my RX 460. Finding this thread was a blessing! Same card, same problem, same broken mosfet and same solution. The GPU indeed works now with one less phase, however I'm having trouble installing drivers. Kzoak did it just work straight out of the box? After driver installation, I get a yellow triangle in device manager and I can't open the AMD Radeon software. GPU Z gives me values all over the place (ie. 3 MegaWatts of power draw or 131% VRM efficiency) and MSI Afterburner is blank. Tried it on Linux and the GPU seems to work. Is there something I can check? Do you think undervolting with a modified BIOS could repair it? Anyhow, RazorWind what about the bootstrap circuit? What should I check?
Thanks
 

RazorWind

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Hi everyone,
I'm new to the forum as I discovered it just yesterday while troubleshooting my RX 460. Finding this thread was a blessing! Same card, same problem, same broken mosfet and same solution. The GPU indeed works now with one less phase, however I'm having trouble installing drivers. Kzoak did it just work straight out of the box? After driver installation, I get a yellow triangle in device manager and I can't open the AMD Radeon software. GPU Z gives me values all over the place (ie. 3 MegaWatts of power draw or 131% VRM efficiency) and MSI Afterburner is blank. Tried it on Linux and the GPU seems to work. Is there something I can check? Do you think undervolting with a modified BIOS could repair it? Anyhow, RazorWind what about the bootstrap circuit? What should I check?
Thanks
A situation like this where the card works with the Windows compatibility driver, but not with the real drivers, is usually an indication of damage to the core, which can happen if one of the high-side MOSFETs fails and shorts the 12V power supply to the core. The fuse that I told kodaf56 to replace is there to help prevent this, but it's not always successful. It's possible something else is wrong, though, if it really does work in Linux, but not Windows. Can you post a screenshot of what GPU-Z shows, and some photos of the card in its current state?

Before you can troubleshoot the bootstrap circuit, you'd need to get the affected phase actually repaired, meaning you need a replacement for the failed MOSFET. once you do that, you need to figure out which of the pins on the phase driver is the boostrap pin, which you can do by looking at the datasheet for that IC. You'd then check the voltage to ground at that pin against whatever the spec is in the datasheet. Typically, this will be something like VCC - silicon diode voltage drop + Vout.

So, if Vcc for the phase driver is 7V, the silicon diode voltage drop is 0.5V, and Vout for this VRM is something like 1.2V, you'd be looking for a value of about 7.7V on the bootstrap pin with the VRM running. You would also want to make sure that you do not have 0 ohms between the bootstrap pins and the VRM's output coils, which would indicate a short through the bootstrap capacitor.

Edit: When you say the card works in Linux, are you using the real AMD drivers, or the compatibility driver that comes with most distros? It's been a while since I messed with Linux as a desktop OS, but my recollection is that neither AMD nor Nvidia offer an open source driver, so to get a powerful graphics card working properly, you still have to download their driver package and install it.
 
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Halon

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Edit: When you say the card works in Linux, are you using the real AMD drivers, or the compatibility driver that comes with most distros? It's been a while since I messed with Linux as a desktop OS, but my recollection is that neither AMD nor Nvidia offer an open source driver, so to get a powerful graphics card working properly, you still have to download their driver package and install it.
Radeons have had solid OSS drivers for years - even RDNA kit works. If it’s an RX 460, it’s likely he’s running the stock open drivers.
 

GabboDoc

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A situation like this where the card works with the Windows compatibility driver, but not with the real drivers, is usually an indication of damage to the core, which can happen if one of the high-side MOSFETs fails and shorts the 12V power supply to the core. The fuse that I told kodaf56 to replace is there to help prevent this, but it's not always successful. It's possible something else is wrong, though, if it really does work in Linux, but not Windows. Can you post a screenshot of what GPU-Z shows, and some photos of the card in its current state?

Before you can troubleshoot the bootstrap circuit, you'd need to get the affected phase actually repaired, meaning you need a replacement for the failed MOSFET. once you do that, you need to figure out which of the pins on the phase driver is the boostrap pin, which you can do by looking at the datasheet for that IC. You'd then check the voltage to ground at that pin against whatever the spec is in the datasheet. Typically, this will be something like VCC - silicon diode voltage drop + Vout.

So, if Vcc for the phase driver is 7V, the silicon diode voltage drop is 0.5V, and Vout for this VRM is something like 1.2V, you'd be looking for a value of about 7.7V on the bootstrap pin with the VRM running. You would also want to make sure that you do not have 0 ohms between the bootstrap pins and the VRM's output coils, which would indicate a short through the bootstrap capacitor.

Edit: When you say the card works in Linux, are you using the real AMD drivers, or the compatibility driver that comes with most distros? It's been a while since I messed with Linux as a desktop OS, but my recollection is that neither AMD nor Nvidia offer an open source driver, so to get a powerful graphics card working properly, you still have to download their driver package and install it.
Soooooo, I'm back with great news. While surfing the Internet I stumbled across a thread on another website and the suggested solution did in fact work for me! All I had to do is to reflash the VBIOS and now it's working flawlessly! I've ordered new MOSFETs but in the meanwhile I'll just underclock it. Yes, when in Linux I was using the stock open drivers.
Thanks for the info about troubleshooting the bootstrap circuit. What about the frequency thing that should be checked?
 
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RazorWind

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Soooooo, I'm back with great news. While surfing the Internet I stumbled across a thread on another website and the suggested solution did in fact work for me! All I had to do is to reflash the VBIOS and now it's working flawlessly! I've ordered new MOSFETs but in the meanwhile I'll just underclock it. Yes, when in Linux I was using the stock open drivers.
Thanks for the info about troubleshooting the bootstrap circuit. What about the frequency thing that should be checked?
If you're talking about the gate pin duty cycle, what you do is put your multimeter or o-scope in duty cycle (that is, percentage) mode and probe the gate pins on that affected VRM phase while it's running. What you're looking for is high single digits on the high side gate (say, 8ish percent), and around 90 percent on the low side, but such that the total is less than 100. If you're over 100, you need to troubleshoot why, which likely has to do with the bootstrap circuit or low input voltage to the card.
 

Kzoak

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Hi everyone,
I'm new to the forum as I discovered it just yesterday while troubleshooting my RX 460. Finding this thread was a blessing! Same card, same problem, same broken mosfet and same solution. The GPU indeed works now with one less phase, however I'm having trouble installing drivers. Kzoak did it just work straight out of the box? After driver installation, I get a yellow triangle in device manager and I can't open the AMD Radeon software. GPU Z gives me values all over the place (ie. 3 MegaWatts of power draw or 131% VRM efficiency) and MSI Afterburner is blank. Tried it on Linux and the GPU seems to work. Is there something I can check? Do you think undervolting with a modified BIOS could repair it? Anyhow, RazorWind what about the bootstrap circuit? What should I check?
Thanks
Drivers didn't work at the beginning. System didn't even detect the card correctly. I've written about it in here: https://hardforum.com/threads/solved-rx-460-blown-fuse.1992996/post-1044519704
But if it works right now that doesn't matter, but I didn't have to flash the vBIOS. I cleared CMOS (Motherboard's BIOS as I had fast boot enabled and thought that it can cause problems) and then it worked.

Turns out 4 of us (RazorWind and 3 RX460 owners) will solve the mystery of Gigabyte RX460. I'm waiting for some news about bootstrap circuit as I can't measure that ;)
 

RazorWind

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Would anyone be interested in sending me one of these affected cards?
Drivers didn't work at the beginning. System didn't even detect the card correctly. I've written about it in here: https://hardforum.com/threads/solved-rx-460-blown-fuse.1992996/post-1044519704
But if it works right now that doesn't matter, but I didn't have to flash the vBIOS. I cleared CMOS (Motherboard's BIOS as I had fast boot enabled and thought that it can cause problems) and then it worked.

Turns out 4 of us (RazorWind and 3 RX460 owners) will solve the mystery of Gigabyte RX460. I'm waiting for some news about bootstrap circuit as I can't measure that ;)
Can you read the markings on the phase drivers off of them and post them here? Also, they should have a tiny marking at one corner that indicates which is pin 1. Can you mark up one of your photos to illustrate this and post it here?

The phase driver ICs are the tiny square ones that appear to have 8 pins on the back of the card, near the MOSFETs.
 

Kzoak

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Would anyone be interested in sending me one of these affected cards?

Can you read the markings on the phase drivers off of them and post them here? Also, they should have a tiny marking at one corner that indicates which is pin 1. Can you mark up one of your photos to illustrate this and post it here?

The phase driver ICs are the tiny square ones that appear to have 8 pins on the back of the card, near the MOSFETs.
Fortunately I've read it before assembling the card again.

1586947830873.png

Pin 1 is left top corner (it's indicated on the motherboard).
The controller is apparently well known and has been used in many other AMD cards before. It's NCP81022 (4 + 1 phases). Documentation is available online.
 

RazorWind

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Fortunately I've read it before assembling the card again.

View attachment 238012

Pin 1 is left top corner (it's indicated on the motherboard).
The controller is apparently well known and has been used in many other AMD cards before. It's NCP81022 (4 + 1 phases). Documentation is available online.
No, not that one. This one.

324954_IMG_20190629_183918.jpg

You mentioned the NCP81161 before. Is that what it is? The marking on it would be "A4M" apparently. It looks like there's one on the other side as well.

If that's the case, then you need to figure out which of the capacitors in that area is connected to pin 1 on it - bottom left in that image. You can use a safety pin wrapped around your multimeter probe to make the tip finer if you need to, so you can hit the pins on it.

The bootstrap cap is supposed to be placed as close as possible to that pin, so it's likely one of the ones in close proximity there. Once you find it, remove it and check its capacitance.
 

kodaf56

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No, not that one. This one.

View attachment 238025

You mentioned the NCP81161 before. Is that what it is? The marking on it would be "A4M" apparently. It looks like there's one on the other side as well.

If that's the case, then you need to figure out which of the capacitors in that area is connected to pin 1 on it - bottom left in that image. You can use a safety pin wrapped around your multimeter probe to make the tip finer if you need to, so you can hit the pins on it.

The bootstrap cap is supposed to be placed as close as possible to that pin, so it's likely one of the ones in close proximity there. Once you find it, remove it and check its capacitance.
I checked that on my card and I found a capacitor nearby connected to pin 1 - I pointed it on the image. I'm gonna remove it and check its capacitance later.
339667_324954_IMG_20190629_183918.jpg
 

RazorWind

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Don't forget to check the health of those zero ohm resistors next to the cap, too. They should be zero ohms, and connected between the cap and the bootstrap pin (pin 1). The other side of the cap should be connected to the phase output.

One possibility is that it's not the capacitor or resistors that failed, but the phase driver itself. They're cheap, and relatively easy to replace if you have access to hot air.
https://www.ebay.com/itm/5-pcs-New-...074739?hash=item3652202e73:g:nOkAAOSwlLlcFE8C

I'm really not sure how you'd diagnose that conclusively, short of just replacing them, and the dead mosfet, and then running the card for a while to see if it dies again.
 

Kzoak

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Don't forget to check the health of those zero ohm resistors next to the cap, too. They should be zero ohms, and connected between the cap and the bootstrap pin (pin 1). The other side of the cap should be connected to the phase output.

One possibility is that it's not the capacitor or resistors that failed, but the phase driver itself. They're cheap, and relatively easy to replace if you have access to hot air.
https://www.ebay.com/itm/5-pcs-New-...074739?hash=item3652202e73:g:nOkAAOSwlLlcFE8C

I'm really not sure how you'd diagnose that conclusively, short of just replacing them, and the dead mosfet, and then running the card for a while to see if it dies again.
I could buy it and try it. Does it have to be A4N? Or can it be anything "NCP81161" like A4F, A4L etc.? I guess it's just a marking on the same thing.

I removed the card today to check if these are indeed A4Ns (they are). I didn't do that previously as I thought it could lead to some problems and it did. After plugging the card back, the PC wouldn't start with it (fans spin, but card wasn't detected). Few starts later still the same thing. Turning AC on/off didn't change anything. Only after clearing the CMOS, the MOBO made some kind of self check (like after every CMOS clearing) restarted itself and booted successfully displaying picture. So I guess these A4N (NCP81161) chips are a good guess. Unless it's the capacitor ;) To check the cap I guess I should remove two of them (for each phase) and measure them to see if they have the same values (because they should?).

BTW I'm trying to understand something here.
I mentioned NCP81022 (4 + 1 phase) and it's one chip in the front. You said NCP81161 and they are there too (on the other side where you marked them).
In the front of the card I can see 4 + 1 phases (high and low side mosfets). On the other side these 4 phases have low side mosfets only (marking K0393).
Do I guess correctly that they are connected with the high side mosfets in the front, so the current given by high side mosfet is split between two low side mosfets?
IMG_20200502_111453.jpg
 
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