Extremely loud, sharp crack!

Greetings!

In my office I have two machines, side-by-side. Yesterday, on machine #1, I did a monitor tune-up of the Samsung SyncMaster 950b monitor (color adjustment, etc. using Samsung Natural Color software). I then began work using machine #2. All the while, machine #1 is on (screensaver activated). Then about a hour later I heard a extremely loud, sharp crack in the region of machine #1. It sounded like a firecracker or even a pistol being fired -- or, if you ever heard it, a high-voltage discharge or large capacitor exploding!

Dazed for a moment I looked over at the machine thinking it was fried only to see it rebooting. All seemed okay. I turned the machine off and opened the box up -- nothing obvious. I looked around and checked all electrical connections - nada. I restarted the machine - all okay. In fact, the machine is working well. Examining it closely today I find nothing burned, etc. I am very puzzled to say the least.

Questions:

What in the world could this have been? Could there have been a high-voltage discharge in the monitor? Yet, it works fine. Would this have been sufficient to cause the machine to reboot? I lean towards the monitor as being the problem because if it were the box power supply the sound would have been muffled instead of the loud, sharp, report I heard.

Thanks for commenting!

janusz

Unless you've got the tower for machine #1 enclosed, I would expect the noise to be just as loud from the power supply as from the monitor. And the fact that it caused the PC to reboot would make me suspect the PSU rather than the monitor. Have a good sniff of both and see if you can detect any smell of burnt insulation or an ozone smell.

off the top of my head did you check the cd drive ?

That samsung software you were running, was it on CD. If so I would do as TheGorx suggested: check the cd tray. The cd might have exploded. That's about what it sounds like (I know first hand:eek:)

TheGorx and DrMDJ make a good point the sound you're describing is very similar to when a CD explodes but I don't remember the computer rebooting when it happened to me.

Nothing in the CD drive. The "software" is a Samsung Utility that installs when the monitor drivers were originally installed -- it sits in the taskbar tray. I can understand how a CD might make a loud noise as it shatters. The sound was very distinct - more of a loud crack (cracking a whip?) sound. Immediately afterwards I looked over the monitor and the box but never smelled anything with an electrical burn smell. No smoke. :)

I have examined both the monitor and the inside of the box -- visual -- nothing to indicate a problem. I had no easy way of looking inside the PS box but it seemed okay. I ran the system for about 30 minutes. I adjusted the monitor, etc. The box ran cool without a glitch.

I know the PS supply seems a logical choice but what could "explode" like that and still operate? At this point the system is shutdown until I can examine things closer to determine the cause.

janusz

Did you check you power lead plugs[ from the mains] for scorching or abrasions as it does sound like a temporary short?

Exploded roach anyone? :p Laugh if you like,but i've seen it happen when one crawled inside a monitor for the warmth...

Ridgerunr - Ummmmm. I've not seen any roaches around but it's possible, I suppose. Or a spider or any insect. Plausible.

What about a dust-bunny? I keep everything pretty clean but with those cooling slots/vents on monitors it's pretty hard to prevent dust from NOT getting inside. I wonder. An arc across two hot terminals and ZAP! No evidence to speak of. :)

104456- great suggestion. I traced the connections all the way to the wall and nothing burned, etc. The power from the system goes to a surge protection switchbox and then connects to UPS. The surge protection switchbox is in good working order - no burned places, etc. Both systems are connected to UPS and the UPS is just fine. With such a loud, sharp crack one would think there would be evidence somewhere -- if not physical at least electrical performance problems due to damaged circuit.

The fact that the system rebooted would seem to indicate the problem is not the monitor but I wonder . . . could a high-voltage discharge cause a momentary system voltage drop to cause system reboot?

I bring up the monitor again because of my perception of where the sound originated. If it were the box PS, the sound would have been just to my left, about 30 degree left head turn. However, the sound seemed to have come from some point further to my left - at or above the monitor or beyond the monitor - at about 75 degree left head turn.

At this point I am reluctant to turn the machine on. Man, I don't want to open up the monitor - even to look - but I guess that is what I will have to do. Another learning experience. Urmph.

janusz

As you say it rebooted and your on an UPS i would suggest the problem lies on the mains side possibly within or around the UPS.

Is the monitor plugged into the back of the PC using the built-in PSU or does it have a separate connection into your surge-protector or UPS?

If it was plugged into the system's PSU, then a momentary problem in the monitor COULD cause the listed problem (still rather unlikely), but if a separate electrical connection - shouldn't have.

The one thing I haven't seen mentioned is the surge-protector itself... a momentary surge certainly could have fired a fuse/breaker/crowbar circuit, etc. in the power strip itself... but regardless, I wouldn't expect everything to still be running ok... hmmmm - strange...

:confused:

Some sort of build up of electricity that then discharged causing the PC to reboot but works fine afterwards.

I won't say I had the same problem but I had a problem with my TV http://discussions.virtualdr.com/sho...hreadid=151544 that hasn't come back since and the 'ticking' sound was quite loud.

104456 - The UPS is right under machine #2 (which was on at the time) - about 5 feet away from machine #1 (the 'problem' one). Machine #1 is connected to the UPS via the surge protector switch panel. All connections good. No burnt marks. The UPS then goes into the wall outlet. I have checked these connections -- All check out okay. Again this is away from where I heard the sound but it is a possibility.

shiva_42 - The monitor is connected to the switch panel. I'm sure you have seen these panels. Looks something like this: http://www.homenethelp.com/buy/item.asp?id=232538 It is a flat low profile: 2" high and about 12" wide and 12" deep. The monitor and printer are connected to the back of the panel. On the front panel are rocker switch: main panel switch and individual switches for the monitor and printer. Yes, they all work fine!

I suppose that the surge protecton panel could have blown a componentm - like a MOV. It is a few years old. I assume that this one uses MOV (metal-oxide-varistors) which are normally wired across the lines.

Ummmm, I just did a quick Google search and found these comments re MOVs:

"MOV based surge protection units are prone to failure, have problems with large surges and can catch on fire or explode."

"And finally, MOV-based, shunt-mode suppressors can, and occasionally do, get hot, explode, and/or catch fire, posing a serious threat to safety and property."

"They've also been known to explode and burn ...."

I think that the surge protection panel with the MOVs has now move up to number one on the list of probable causes. It would also explain why everything is still working - just lost surge protection. It would also explain the restart since this directly effects power to the computer box also. Explosion sure fits the description because it reminded me of a capacitor exploding!

Your comments? What odds would YOU place on this as being the cause of the mysterious loud crack sound?

I will open it up tomorrow and let you know what I find.

janusz

Do they still work after the MOV is blown ?

I would have thought they would stopp working so that you don't carry on using your PC unprotected ?

After all if it blows when your not about, how would you know if its protecting you from surges or not ?

Nix - here's what I've learned . . .

No. Once blown, it's shot.

They can stop working and leave your machine unprotected. THAT's the problem with MOVs. They deteriorate with voltage spike hits and when they do they lose their clamping voltage levels (gets higher and protects less).

Yes, a defective MOV would leave you unprotected -- no real way to know if it's working and clamping voltages at safe level. In fact, there is do way to predict how long it will last - it depends on how many hits the MOVs are exposed to. They are shunt or parallel connected so if it finally "opens" or "blows" (break in MOV shunt circuit) things would still work but unprotected. If it "shorts" (makes direct contact) across the lines then boom! . . . leaving an open circuit (MOV no longer connected across lines) in most cases. MOVs get hot and can explode and cause fire hazard.

I use the under-monitor surge protection panel because I like the switch control feature (I plan to remove the MOVs and leave it as pure switch box). I have UPS that handles voltage spikes, surges, etc. I made the move long ago after getting strange spontaneous reboots on my machine. UPS cured it.

janusz