think i fried my mobo

[Kingfish999]

so im building a computer for our business using parts I had laying around. it was working great but it had a lot of fans which were really noisy (7+ 40mm just for the case). what I like to do usually is take a 3 position toggle switch (on/off/on) and wire all the fans to it so they can run on 5volt, 12 volts, or off (using a separate rail form everything else of course). unfortunate my multimeter lied and my toggle switch mixed the 5v and 12v. now the thing wont turn on. the light on the board indicates that the board has power. I swapped PSU and still no difference. did I just epic fail and brick it or is there something I should try?

the board is an old Intel DX38BT with a E8400. far from the fastest but still not the worst compared to the 10 year old laptop we use now

 

[Nebulous]

Well I'll confirm what you already know...the board is indeed dead but just to clarify: you stated you used a separate rail from everything else. Are you saying a separate line (molex) from the psu itself?

 

[Kingfish999]

ya. the PSU had 5 +12v rails (IIRC 1 for mobo/cpu, 2 PCIe, 2 Molex\SATA) and I always put the fans with switch on a separate rail than the HDD and CD drives just incase. the toggle switches the +12v (yellow wire on molex) with the +5v (red wire). obviously that would be very bad on anything else but for fans it cuts the speed down by a lot which makes the computer very silent. and when I need full speed for gaming I switch the toggle and its back at its noisy 100%

unfortunately the toggle switch wasn't a normal one like I though. it ended up connecting the 12v and 5v. im assuming that the 12v went into the 5v back into the mobo. at first I was hoping I might have just blew the internal fuse in the PSU but swapping it out showed it wasn't the PSU

 

[Nebulous]

Yup. By crossing the rails you killed the psu and in turn that fried the board. Best to check your other components (hdd & gpu) to be those are still working. Hopefully the chip is still safe. Won't know until you test the chip in another board.

So it's official, the board and psu are dead.

 

[Kingfish999]

PSU is good still. just tried it. just the board dead im guessing. everything else is good too

 

[Kingfish999]

ended up buying a reman Gigabyte GA-EP43T-S3L off ebay. 85$ shipped I didn't really wanna spend but should work fine regardless. boss defiantly wants a somewhat decent computer at our shop

 

[MongGrel]

GL, don't cross the streams.

 

[larrymoencurly]

PSUs are supposed to be protected against rails being connected to one another, and even that old DTK brand 200W described here had such protection. Also if the fans had been connected only to the PSU, the motherboard couldn't have been damaged/ Were any of the RPM signals from the fans were connected to the motherboard?

I'm assuming you had the toggle switch wired so the center connection went to the "+" of the fans, while one of the outer switch connections went to +5V, the other outer switch connection to +12V, and the ground of the fan went to the PSU's ground.

Is it possible that you used a make-before-break switch (connects to the other contact before disconnecting from the contact in use), rather than a much more common break-before-make switch (disconnects before connecting)?

 

[Kingfish999]

ya that's how I normally wire them. its pretty simple

im not sure what kind of switch this is but im defiantly not gonna reuse it. I have a bunch of these toggle switches for our boats. my multimeter shows its defective now. 1 side always connected to the middle some reason no matter what position switch it in. it didn't do that before so im just gonna throw it away and use another testing it extensively. mabey ill add a diode or something to prevent this in the future.

I would think that there would be some sort of protection on the PSU to prevent stuff like this. this board does have a molex connector that plugs into it. it was on a seperate molex strand from PSU but im guessing its on the same rail.

im really hoping I didn't fry the CPU along with the board. I didn't think of that till now. don't have a way to test either

 

[Kingfish999]

alright so an update. got the new mobo in and installed. everything seems to be working fine but apparently the HDD got zapped as well. darn o well at least everything else seemed to survive. was really worried bout the CPU and GPU. this new mobo is pretty cool. might just have to barrow an HDD from my computer till I can get a new one.

 

[larrymoencurly]

There's a good chance the HDD's overvoltage protection diodes shorted and blew the fuses next to them and protected the rest of the circuitry, in which case replacing those parts should allow data recoveryFanc Zabkar's FAQ.

 

[Kingfish999]

cut out the TVS diodes and still doesn't fire up. o well I had the HDD cloned right before anyways so nothing lost. just need to buy another. it was an old 500gb Samsung anwyays

 

[ATMINSIDE]

cut out the TVS diodes and still doesn't fire up. o well I had the HDD cloned right before anyways so nothing lost. just need to buy another

And this is why we stress frequent backups

Glad you got everything sorted out and nothing more was lost!