Aaron707 wrote on 2024-02-07, 01:24:
So my board has been working good and I was trying out some games. The machine was on screen saver then the screen possibly went to sleep when I was doing something else. I tried to wake it but couldn't get any display. So powered it off and back on, still no display. Tried a different GPU, same. Reading about a similar issue earlier in this thread I checked FB8 and it was getting 3.3V on only one side. So removed it and jumpered FB8 (removing the FB it fell apart). Tested again and got some magic smoke (see picture below of bottom of board). Hopefully its not ruined. Pretty sad this happened. Is that burnt trace the ground plane? the side closer to socket measures shorted to ground. And the side of FB8 further from the slot of measures 468ohms to ground . And somehow R30 right next to AGP slot was turned sideways and fell off when touched. What is the value of R30? Any ideas what to check or why I lost video would be greatly appreciated. I think I will set this project aside for today and come back to it later this week with a clear head.
First of all - I just updated the github page with complete schematics, layouts and gerbers, so you're all free to follow along.
Then, to you issue Aaron, the trace that fried is part of the "VCC_3V3_AGP" net - one of two 3.3V power rails going to the AGP slot. The reason it was destroyed is almost certainly a dead short to ground - which if I understand you correctly is what you measured as well. Looking at your photo, I'd venture a guess and say that the short is somewhere really close to the fried area, as that trace is actually thicker right there than at some other places on the same net. If the short was farther away, the thinnest part of the net would likely have melted.
Try removing the AGP card from the slot (to keep VCC_3V3_AGP and VCC_VIO_AGP separated) and locate the point where the burnt trace shorts to ground - that's a good place to start at least.
Not sure why R30 loosened and fell off, might have been desoldered by the heat caused by the short? The (partial?) short probably happened first, then the FB8 was ruined by the increased current, and when you bridged the FB8 footprint, the current melted the trace.
If nothing else was destroyed, if you're able to locate and fix the short and then solder on a good-thickness wire in place of the broken trace, you should hopefully be good to go. Fingers crossed! 😀
Lastly, I don't yet understand why you got the short in the first place - hopefully we'll get to the bottom of this!