The burnt trace on the ISA riser card seems to be B3, which is the +5V supply. Obviously a very high current (tens of amps?) was conducted through it. On the sound card, it also is the +5V trace that is burnt. You get burn marks both on the trace from B3 to the configuration EEPROM (the 8-pin 93C66 chip) and from B29 to the configuration EEPROM. Both B3 and B29 are +5V pins. Possibly you did nothing wrong with the riser card, and the sound card was shorted already before you inserted it to the riser card. Primary suspect would be the ceramic multilayer capacitor CB14 next to the 93C66 chip in that case. Those caps tend to fail short if they are mechanically stressed too much.

The damage is not as bad as it looks. You burnt some of the solder resist lacquer, you can apply nail polish as replacement to restore insulation. Those traces are really wide, so if the trace is broken, it's again easy to fix it. So a repair plan would go along like this: Check for continuity of +5V on the riser card, check for shorts from +5V to GND. If everything is fine, clean the burn marks and apply nail polish. Check the sound card for shorts from +5V to ground. If the sound card is shorted, try to remove CB14. If you can get the short removed from the sound card, it's again cleaning up and applying nail polish. In case the short on the card originated form a shorted capacitor labelled CB, it should be replaced in the long term by a new 100nF multilayer ceramic capacitor.

Smoked the IDE cable once with my first 386 PC back in the day in full view was connected wrong, and nothing affected anything, replaced the cable and all good. Lucky me.

Blew the dying hard drive's motor in beautiful ring of smoke billowed out around the motor's rotor, as power load on a malfunctioning power supply, I was too inexperienced to diagnose and find the source in 1991-ish.

Cheers,

Thank you mkarcher, I'll see if I can get a multimeter and test that out. Best case scenario is that the riser card is fine, and I can use it to put a sound card back in the machine (likely another Vibra 16s). I've never tried soldering before, so I'm not sure that I could replace the cap on the sound card or patch any traces. All of this comes after me figuring out why the thing hasn't been detecting new in box brand name CR2032 batteries (and this machine is one of those that acts up if it doesn't have one). I wouldn't even care if the PC couldn't ever use a sound card again as long as the base system works. The CR2032 issue has been going on for a while now, and I'm stumped.

I didn't know IDE cables could smoke when plugged in backwards. I've killed a drive and motherboard by doing that though, my first and last Quantum Bigfoot drive (not like the thing would've worked for more than 6 months anyways), and my Intel SE440BX-2, which I only paid US$40 for, and was my favorite Slot 1 board out of the ones I've used. It now sells for US$ 150+. I've become very paranoid about making sure the red stripe corresponds with pin 1 on the drive when using IDE cables without keys.

I suspect there may be something off about the PSU in the 486. Sometimes the machine turns itself on if left plugged in, and this happens even if it's only been plugged in and off for ~10 minutes. The PSU itself is from 1995, and has never been cleaned thoroughly because I don't have a torx security bit to open it. One owner before the guy that sold it to me seems to have been an automotive shop gauging by the amount of chemical scented black dust that was all over the inside of the computer (and is still in the PSU), as well as software to prepare you to take automotive certification tests on the HDD.

In 2013, I was moving my Athlon 64 build into another case since the original case broke down a few years prior and the case I was using after that one (a cheap $20 Diablotek case from eBay) was too cramped and was pretty flimsy. I managed to plug the floppy drive power cable in incorrectly and when I turned it on, the graphics card did a continuous beep and smoke came out from where the power connector was on the floppy drive. I had to replace the power supply and floppy drive. Funnily enough, I went through two different cheap power supplies (a 480W Logisys and a 500W Apevia) before I settled on the one I'm using with it now (a 600W EVGA). The Logisys PSU lasted for a year before it died completely, and the Apevia one kept causing the hard drive to restart itself (possibly bad SATA connectors). Finding a suitable replacement that wasn't complete garbage was tough because I needed at least two Molex connectors (for the disc drive and graphics card) and a floppy drive connector.

I've had a PSU die on me while I was playing Garry's Mod on my main rig back in 2015. It stunk of ozone badly, but never smoked and also never damaged any components. Can't remember the brand, some cheap thing that came out of my mom's old gaming PC she bought from a local computer store. Of course they cheaped out on the PSU, why wouldn't they?

I've been lucky enough to have never plugged in a power connector wrong, knock on wood. I remember when I started working on the 486 (my first ever AT system), I was extremely paranoid about making sure black was to black because I had heard too many stories of what would happen if it wasn't.

It's been many years, I had a P3B-F motherboard back when it was still state of the start.

It was running a little hot so I decked out my case with 3-4 fans and populated all of the fan headers with those.

The board did not like that. It smoked heavily, all of the fans stopped and yet, it still continued working.

I used it for a few years but the fan controller was toast. Had to power my fans via IDE power adapters directly.

I can't remember any other instances of magic smoke, so I guess I'm pretty lucky.

Why would they put all those fan headers in there if the controller couldn't handle it? I've had other 440BX boards with three fan headers and ran all three (CPU, intake, exhaust) at the same time and never had any issues, so it must be something specific to that board, maybe the fan controller just wasn't enough for all the fans. You got lucky that when the fan controller smoked, whatever was happening didn't damage the rest of the board.

I remember the first time I let out the magic smoke! I hadn't even gotten into retro computing yet.

An old friend of mine had an old Pentium MMX, something like a 166MHz overclocked to 200MHz or so, with something like 40MB of ram and a PCI Voodoo 3.
He had his system completely outside of the case so he could overclock it better.

At some point as we were overclocking his CPU I got the luminous idea to make the fan spin the other way around, perhaps that would improve the cooling somehow!
And as we didn't want to screw the fan from the heatsink, I thought it was a great idea to simply plug the fan connector to the motherboard backwards to make the fan spin in the different direction! Damn the plug wouldn't fit, oh well I'll just force it in what could possibly go wrong! 😁
Well, magic smoke and our little overclocking adventure ended prematurely.🙄

Thankfully nothing else got damaged. I think he ran his system like this without a CPU fan for a while completely outside of the case until he got an AthlonXP.

schmatzler wrote on 2022-12-31, 02:10:

It's been many years, I had a P3B-F motherboard back when it was still state of the start. […]
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It's been many years, I had a P3B-F motherboard back when it was still state of the start.

It was running a little hot so I decked out my case with 3-4 fans and populated all of the fan headers with those.

The board did not like that. It smoked heavily, all of the fans stopped and yet, it still continued working.

I used it for a few years but the fan controller was toast. Had to power my fans via IDE power adapters directly.

I can't remember any other instances of magic smoke, so I guess I'm pretty lucky.

May I ask what kind of fans did you try to use?
It may be possible that you added newer fans with more power draw than your board was able to handle?
Back when these boards were made, 8cm fans were barely a standard yet, let alone larger ones.

Haven't had a magic smoke experience for a long time. But had it today with a NOS AOpen IDE CD drive. When I powered it up I immediately smelled something was wrong.

Strange thing it was a chip and not a capacitor or resistor. First time for me but fortunately nothing else was damaged. But I can throw the CD drive away. 🙁

I've described this elsewhere on Vogons but my first encounter with magic smoke was troubleshooting my old 386 and I don't even know how it happened but the Soundblaster released its magic smoke. I can't remember but it was probably a SB16 with CD rom interface attached. Anyways I reset the card in the motherboard and it fired up fine. Never had a problem with that PC or the board again, not sure what I smoked but it must have somehow been for something I didnt use.

Oh I should mention I was drinking heavily that day.