Heatsink fan burned out now computer is dead.

[bluebuda]

So I attached a new heatsink to my computer, after doing so I turned my computer on and the fan on the heatsink started to smoke, it never even spun at all, just smoked, then my computer would not turn back on, dead.

I used the proper heatsink, I replaced a standard square heatsink on my HP DX7500 with a round copper core heatsink, obviously I used thermal paste, I connected it right, I think I just got screwed, bought this POS off Ebay, they sent me the wrong heatsink at first, then when I told them about it they sent this other heatsink, which I'm sure killed my motherboard.

I didn't even think a heatsink fan could go bad and take the motherboard with it. Looks like I will be buying a replacement motherboard now.

No power light turns on, the case fan spins for about 30 seconds, and stops, that's all.

Anyone have any ideas, anyone think I'm diagnosing this wrong?

My thoughts are to buy a replacement board that can be returned if I need to.

Fuck Ebay, everything was working great until these buttholes. LOL Funny thing is that this is like the 5th or 6th person trying to screw me in a row lately, has Ebay become nothing more than con artists or have I just gotten unlucky that many times in a row. I mean WTF, they have 90 + positive ratings and have been around for a while, and I read all the fine print, am I really this unlucky or is Ebay really turning into a real con artist haven?

[shovenose]

Re: Heatsink fan burned out now computer is dead.

Well, not only is eBay experiences getting worse for buyers it seems (even though I've never had any issues), also sellers like me are getting fucked too...

[rhomanski]

Re: Heatsink fan burned out now computer is dead.

It goes in cycles for me. About 5 years ago everything I bid on was a blatant lie either in condition or someway. I backed off for about a year. When I came back I started getting good stuff again. Only occasionally getting ripped off.

I bought a tape deck in the eighties and it still works perfect. I thought I might get another one. Three times I won the bid. One was even described as having "just been serviced". When I got it, the doors wouldn't open and neither well will reverse. The other two were about as bad. All three sellers had hundreds to thousands of transactions and almost 100% positive results. The luck of the draw I guess.

[Phaihn]

Re: Heatsink fan burned out now computer is dead.

ebay is really buyer beware. certain items i would never buy from ebay would rather get it at a local store if i can or i order it from memoryexpress

[gilly1984]

Re: Heatsink fan burned out now computer is dead.

would a shorted fan no just trip the PSU out?

have you checked to see if a different PSU will get the mobo going again?

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

I did change the PSU with a known working PSU, no change.

I did a bad thing and took the CPU and stuck it in another MOBO, thank God it fired up and didn't take down another MOBO, so my processor was not damaged.

Everything is still good except my MOBO, I was wondering if it blew a fuse on the board somewhere, it's a HP DX7500 MOBO if anyone would know about this stuff.

I can't believe a heatsink fan can blow a MOBO, but it appears that , yes, yes it can.

Stupid thing is when you google it no one talks about this being possible, all that comes up is bad CPU blowing good MOBO, or bad MOBO blowing good CPU, Google giving you the results you're looking for my ass. LOL

[gilly1984]

Re: Heatsink fan burned out now computer is dead.

The only fuses i have seen on mobos is for usbs I think?

Have you checked the voltage regs on the board?

I am no expert but the time I have spent here I know to get the multimeter out and check everything.

Check for shorts around the regs.

If you really want to save it, post some pics and give the guys Here some readings.

I would do it for the learning experience, the board isnt worth spending money on.

Boards are very cheap to replace. Is it a standard m-ATX?

[RJARRRPCGP]

Re: Heatsink fan burned out now computer is dead.

Sounds like the fan circuit is messed up or a cap got damaged.

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

Alright, well if anyone wants to try their hand at helping me fix my MOBO here are the pictures, it can't get any more dead than it already is. LOL

A background on me, I have decent solder skills, but I'm not capable of supersmall repairs, I can do repairs down to about the size of surface mount resistors, capacitors, and so on, no smaller.

I took lots of pictures, there is no noticeable physical damage, I.E. no blown caps or anything like that.

I started at the bottom left corner of the MOBO, and worked my way up in rows which I called a pass, when I got to the top I returned to the bottom of the board and started a new pass until I reached the end.

I also took on crappy pic of the whole board just for reference.

My tools include, analog and digital Multi Meter, Capacitor meter, and a home made TV oscilloscope, although I do have access to a real oscilloscope if needs be.

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

Here is the rest.

Also I screwed up, I posted pass 1 pic 1 last, sorry.

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

Sounds like the fan circuit is messed up or a cap got damaged.

If you mean the circuit on the fan I put the old haetsink and fan back in place, no good, still a dead MOBO, if you mean the circuit that controls the fan on the MOBO I would love to know where to find it.

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

I did some poking around on my board and opened up the fan that killed my computer and discovered a couple of things.

1 a diode of the fan itself split in half, I don't know if it was this way before I plugged it in, or if it cracked after, my guess would be after.

2 I traced some of the leads back a bit on the board, hard to do without schematics considering the boards are 5 and 7 layer, I found a 100uf 16 v cap the 12v goes back to as well as what look like two super small surface mount resistors that I'm not sure I could replace, not sure I couldn't either. I tested the cap in circuit and it read around 99.8uf which could be wrong considering it's in circuit.

3 I also traced the speed control and rpm sensor leads to a surface mount resistor and what appears to be a transistor or diode, I'm not 100% on that one all it has written on it is L43.

So, anyone have any guesses where to go next? Besides the trash that is because that's an obvious fix for this. LOL

Here are three pictures for you if you enjoy solving problems like I do. XD

[RJARRRPCGP]

Re: Heatsink fan burned out now computer is dead.

If you mean the circuit on the fan I put the old haetsink and fan back in place, no good, still a dead MOBO, if you mean the circuit that controls the fan on the MOBO I would love to know where to find it.

Yes, the part that controls the fan plug.

[kaboom]

Re: Heatsink fan burned out now computer is dead.

a diode of the fan itself split in half, I don't know if it was this way before I plugged it in, or if it cracked after, my guess would be after.

If you're certain you plugged it in properly, I'm betting that someone before you hooked that up with the polarity reversed. That diode is connected across the 12V input on that fan, reverse biased. The idea is that should it be connected backwards, this diode will conduct, blowing a fuse. But there are usually no fuses on fan headers anymore.

Someone reversed that fan's polarity, and the diode conducted and shorted. You put a short across your fan header and applied power!

There's a 12V trace somewhere burned open on that board. When the soft switching tries to bring up the board, whatever else on that 12 volt circuit no longer operates. Something times out because the proper signals are not exchanged. Then the PS-ON signal is dropped, and the PS shuts off.

It may be possible to back feed that 12V line, even if the bad spot is between layers, as long as it comes out on either the front or the back.

[bluebuda]

Re: Heatsink fan burned out now computer is dead.

If you're certain you plugged it in properly, I'm betting that someone before you hooked that up with the polarity reversed. That diode is connected across the 12V input on that fan, reverse biased. The idea is that should it be connected backwards, this diode will conduct, blowing a fuse. But there are usually no fuses on fan headers anymore.

Someone reversed that fan's polarity, and the diode conducted and shorted. You put a short across your fan header and applied power!

There's a 12V trace somewhere burned open on that board. When the soft switching tries to bring up the board, whatever else on that 12 volt circuit no longer operates. Something times out because the proper signals are not exchanged. Then the PS-ON signal is dropped, and the PS shuts off.

It may be possible to back feed that 12V line, even if the bad spot is between layers, as long as it comes out on either the front or the back.

Yeah, that's a great idea kaboom, I'm not super familiar with computer motherboard layout's I usually fix TV's, much easier to work on, but this is fun, I'm learning a great deal as I go.

So from what I can tell the ATX 24 pin molex has two +12v and the 4 pin CPU molex has two +12v, wondering which lead to trace?

Also, when you say back feed the circuit I'm guessing you're suggesting I hook up a +12V power supply to the fan plug on the motherboard and follow the current back to the molex with my multimeter? Did I understand you correctly?

Providing no power is being fed to the MOBO through the PSU at all, the motherboard would be void of all power except the +12v I'm feeding through the fan plug.

Just thinking about it a bit makes me think I'm misunderstanding, seems I would run into some problems with diodes and could damage the board further.

Perhaps if you could link a tutorial to back feeding if one exists.

[kaboom]

Re: Heatsink fan burned out now computer is dead.

Also, when you say back feed the circuit I'm guessing you're suggesting I hook up a +12V power supply to the fan plug on the motherboard and follow the current back to the molex with my multimeter? Did I understand you correctly?

You're on the right track. Depending on how that fan header's power is controlled. If the low side of the fan is switched to ground with either an NPN transistor or an N-channel MOSFET, this will be easier.


In this case, the +12v pin on that fan header is the same trace and circuit that eventually goes back to the 12V wire from the ATX connector. It should only go back to that- the CPU's 12V supply should be seperate.

The trace that feeds the fan also feeds chips and other ckts upstream of where the fan ckt is tapped off. It sounds like you've got an open between one of the main 12v points, but before the chips, and even further upstream of the fan takeoff.

Using a lowish value resistor (3-10 ohms), just go from one of the yellow wires to the 12v pin on that fan header. Also put an ammeter in series.

-This will only work if the fan's low side is controlled by an NPN transistor or an N-channel MOSFET-

It works because with the low side "controlled," the high side (12V pin) will be uninterrupted all the way back to the ATX connector.