1. Home
  2. ⏚ Electrical Engineering
  3. Feedback destroying my computers...

Feedback destroying my computers...

Hi folks,

I've got an issue with my PC and some feedback that's going on which is destroying my PC's. It's popped three mother boards already.

This is not really a computer related question so bare with me. :)

I have PC with a number of peripherals attached such as routers, USB drives, active speakers etc. Everything, barring the speakers, runs from it's own 12V PSU. Only monitor is a switched PSU, everything else, old style. The speakers have their own internal PSU which I would imagine is not a switched flavour.

On the first occasion, I was connecting a USB drive, with it's own external PSU, to the PCU and as the casing of the connector touched the PC case, a spark jumped, not a small one mind you, nice and fat and yellow, between the two. The PC fell silent. Motherboard was dead.

Second and third occasions, I was unplugging either the monitor or a USB drive (Different one) and while I noticed no sparks, the PC fell silent. Again, both times MB dead.

Now why would the be a PD between PC case and ground on USB drive? Same for the monitor. The mains plug is correctly earthed and everything is plugged into a strip plug.

This has happened in two different homes now. After the first occasion, I replaced everything in the PC. Only "old" thing is the case. All innards are new. As for the common devices between the first and last occasion, only the monitor (External switched, 12V) and the speakers are the same.

I get the lovely hum when I touch the speaker plug against the PC case. Nice crackle to.

How can I go about tracing the culprit? Any easy way? Process of elimination is difficult as I only have one monitor. The speakers I could do without for a while.

Also, this seems to happen randomly. Not happened for 6 months now but happened today. I can rule out (99% sure) static as the air is rather humid and try as I might on the carpet, I get non. Also, the previous attempt was on a wooden floor.

This is becoming expensive and frustrating now.

Thanks in advance for any pointers.

Regards, Crispin

Reply to
crispin.proctor
Loading thread data ...

The problem is your name.

You are destined to fry your consumer electronics gear.

It's fate. :-]

Reply to
ChairmanOfTheBored

Posting with NO PANTS is ALLOWED!

Thanks, Don

Reply to
Don Salad

Soldering with NO PANTS is also Allowed. But will probably produce better stories.

Dave

Reply to
David DeLaney

  1. Faulty mains supply lead / connector contacts, earth is open
  2. Steel body of PC PSU is not connected to metal case (varnish?)
  3. System connected to appliance with large Live-Earth leakage (TV?)
  4. Monitor (remaining common component) has faulty inlet filters.

Or give up and buy a laptop :-)

-- Adrian C

Reply to
Adrian C

An idea that hasn't been mentioned yet is the 'grounding conductor' in your wiring (the 'third prong'). If the outlets are mis-wired you may have a voltage on the third prong and that would put a voltage on the frame of some of your equipment. Even worse would be if one outlet has this problem and another outlet doesn't. So connecting a USB device powered from one outlet to the USB port on the computer, when the 'metal frame' of one touches the other you would short the stray voltage from the mis-wired outlet to ground through the correctly-wired outlet.

If you are 'handy' with a multi-meter, measure the voltage between the ground prong of several outlets (from the ground prong of your PC outlet to the ground prong of several other outlets). If you find any voltage at all, there is something wrong. These 'grounding conductors' should not normally carry any current and should all be connected to the same bus inside the service panel.

One way this could be mis-wired is to not have a ground wire back to the service panel and instead just a jumper between the third-prong screw and the neutral conductor. That would put a couple of volts on the third-prong (whatever voltage drop there is along the neutral conductor when loaded).

daestrom

Reply to
daestrom

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.