Help with noise

Hi everyone,


We have some serious problem with a PC that used to work for months.
We tested everything, tried to replace the PC for another one (and then one more). All PC's seam to work just great for some time (sometimes couple of hours, sometimes couple of days)
and then they lock up (freeze). This seam to be random and only when PC is running at that place (None of them have any problem
when running in our office). We suspect noise issue. An oscilloscope
was showing high frequency bursts of ca 80Vpp everywhere in the area
PC is installed (this is what we can see without touching anything with the scope's probe!). We tried to disconnect parts of the system in order to identify source but it is impossible to turn of every single piece of equipment (they just have too many of them). Customer claims they didn't install any new equipment and after scratching our heads we are at the point we might need some help. Does anyone know company or individual in the Toronto area that could give us a hand (paid service of course)?

Why not install a UPS and forget about it?

Customer claims they didn't install any new equipment

Click to expand...

Did they by any chance change the carrier frequency on some drive

Hi Pierre,

Thanks for reply.

If course I have have UPS. Actually I suspected UPS as a possible cause so we tried to run the system without it and then we put another one in. Same results...
All grounding in our part of system is done properly. This is not the problem but I've noticed potential difference between grounds of different
equipment. Customer will have to check if everything is tied properly on their side.
I've also inspected all RS232 cables myself. They are all ok but we might need to add optical isolation for each port (just in case...).
Nothing was changed on our equipment (it was running for ca. 2 years now) but the area is crawded with tons of other equipment so I suspect something else changed. Obviously only part of system that suffers is the PCs and we see same problem on the replacement computers. They all behave the same when installed in that environment and they all work fine in our shop.
Any more ideas?

I think Black Box makes sound-proof enclosures for PCs. I know such animals exist, whether or not it's Black Box, because I saw one that would hold an Apple PowerMac G4 to keep the sound from it's fans from disrupting other equipment in a lab environment. Anywho, such an enclosure would keep the noise away from the PC so that it can't interfere with the operation of that PC.

If I'm not mistaken you are taking about audio noise.
Yeah, there is some noise (it's assembly plant) but nothing
nearly that extreme to cause PC to malfunction. Noise
level is about same as in my living room. PC is not exposed
to vibrations or anything else...
Any more ideas?

Just crazy Idea.
Some thing like that happened to me. Someone weld on the machine and hold the ground on electrical pipes so he berned all the isolation of the wires but it was not too bad to cause short cut so I had terrible problems until I found the the reason.

Hi,

just to have more datails the PC is connected to what? via what ports? or interface , etc..

desktop pc?

We tried using a desktop pc in one area of the plant with dismal results. In this case it seemed to be a motherboard/case shielding issue. As in your experience, in the office it worked fine, on the production floor it crashed. Our best guess was emi problems from vfd's and ultrasonic cutters.

We simply moved the pc (and network cable)into a less "noisy" area rather than spend the extra money for an industrial pc.

PC is connected to following:
Com1 : RS422 network (controlled by PC i another machine)
This is connected to our PC through 15ft cable and
B&B converter 422/232 (plugged to COM of our PC)
Com2 : ADAM4000 network (part of our equipment)
Com3 : Spare
Com4 : Q2AS PLC G4-Module (part of CC-Link network)(Mitsubishi)
Com5 : PF3000 (Atlas Copco Tensor)
Com6 : PF3000 (Atlas Copco Tensor)
Com7 : Barcode Scanner (Welch Allyn)
Com8 : Currently Spare
Com9 : Q06H PLC CPU (Mitsubishi)
Com10: Spare

I have participated in the development of vegetable container bags. You must have seen them around. They are transparent plastic bags filled with letuce. The plastice is more rigid than the old bags. They appear sealed but they are not.

Those bags must let air in and out. If you look closely, you will find that there is thousand of very small holes on the plastic material.

Those holes are made with electrical arcs. 50 000 volts and 100 spikes about 1/8" from the plastic surface will arc and pass through the plastic hence the holes.

OK, now the real problem. How to isolate the components around this machine?

There was noise and I mean big time noise.

First you need a Faraday cage... but you already have it in the form of the PC casing.(Is it well grounded)

Second you need to prevent the noise from getting IN!

But are we looking at this problem with the good angle? We assume that the noise is the problem. Is it?

4 things are bad for any electronic components.

-Heat
-Vibration
-Electrical noise
-My Dad

Since my Dad is not close to this system we can rule him out.

-Heat. You can install a small freeware that will show you the CPU temperature realtime. It could be a clue to other problems. Sometimes when the PC is in the office there is a 10° difference and its just what it take to make a big difference. If its borderline, install a better Power supply. One like "Enermax" for instance. Most of the CPU temp. problems comes front the power supply. Pick one with bearings, not sleeves.

-Vibration. If the PC is located in a vibrating environment you should soon see the HD being damage or having bad sectors. Sometimes the operator will hit the PC with his foot. OUCH!!!

E-noise: Hum! That one is trickyer

I have seen more monitor failures than PC failures caused by noise. If you say that the screen freezes then the PC or whats inside it cease to function properly.

How does this happens?

The cause could show they way to isolate the problem. Do you have a memory dump that you could read. What was the last CPU operation before this problem occured?

The screen comes from the graphic card. Its info comes from the bus ... from the Driver ... from the disk ... from the CPU ... the clock ... the memory sticks...it all comes to this: is this catstrofic failure hardware or software related. It could be any of them but my first choice would not be to try and prevent the noise from coming in.

PS: I used to work with G.E. they had some very good technicians very knowledgable about noise. So they will tell you that you have noise. What else is different?

What OS?

It's (pretty lean) install of Win2000 with next to nothing
on top of it (MX Components and our EXE file). All of this was
running for ages (well, considerable time...) and now
(in the last 2-3 weeks) we see that any PC we put in there
will lock up after few hours if not sooner.

Three thoughts

Heat( or cool) - atx power supply fans, cpu fans...environment
dirt -
power supply - is there some seasonal load wreaking havoc with the mains

$0.02

You must hunderstand that these are WAGs (Wild A$$ Gessings) but here is one:

I have seen the power supplyer (Hydro-xxx) drop our feed 10 Volts. They had switch there up-xfgormer's tap because the decreasing demands in the sector... they never told us until we start having some system going bezerk on us.

Our onw xfos had to be readjusted.

Could this be it.

My first choice would still be to check for CPU temperature.

Thanks everyone. I really appreciate all input
even if it's WAG .
Unfortunatelly CPU was cool...
(I never tought I'd wish for CPU to be dead... Oh well, there is always first time...)

I will offer some thoughts but they may be as wild too. I had somewhat similar problems not long ago.

The part I accept as a FACT: The PC's ran for 2+ years no problem.

The part I DO NOT accept as FACT: Nothing has changed in plant.

100 to 1 odds something was added, changed or modified just prior to these problems.

MY FIRST THOUGHT is HARMONICS, I had a similar problem with a PC not too long ago. Harmonics can add power to a line, Harmonics can add power to a NEUTRAL, Harmonics can add power to ground and Harmonics may not be filtered by a UPS or DC power supply. It can wreak havoc with hard drives causing corruption.

Use your scope to look at the PC's 5 and 12 volt supply. If you have a Power Analyzer handy that may offer more. I would definitely test the ground to verify its not ADDING power instead of removing thru Harmonics or any other way.

If you investigate I bet something was upgraded recently that added an AC Drive or something similar to the system that was not there before.