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Power Surges

By shantie ·
I have put the following faults down to storms and power failures but would like to know what actually happens to the system if surged. I have two computers from the same company. First computer was in the home on an UPS but they went away during Xmas and we had a lot of power failures so power was off for quite a few hours due to bad storms, anyway their system was okay except for hard drive making funny clicking noises, replaced that and system okay. They then gave me second computer which was in farm shed on a separate line but not connected to an UPS. Would not boot, discovered a floppy in drive, took that out and system booted, ran for an hour, shut down, next day,tried to restart, no power. changed PSU and booted got message missing operating system. Shut down connected another hard drive, tried to boot no power. Tried a new PSU, no power again. I rechecked all power connections to board and power switch connector, all okay. Think this system had a bad surge also, and my thoughts are that a component was badly damaged and each time try to boot more damage is done, would this be correct and can you explain how this happens. Both systems still had phone lines connected during storms.

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by TheChas In reply to Power Surges

Electrical over-stress is often difficult to deal with. Whether it is ESD (static) lightning, or over voltage, the stressed components can take months to actually fail.

On PCs, I find that voltage surges on the phone lines can cause more problems than power surges on the AC mains.
For any system that is in a rural location, using an external modem can provide better protection to the PC.

Now, what happens to the semi-conductor devices inside a PC when they receive a voltage over-stress?

All semi-conductors are a network of molecular level junctions between dissimilar materials bounded to a metal or ceramic substrate.

Depending on the size (peek voltage) and duration (time) of a surge the junctions in the current path that the surge takes can either:
remain intact;
weaken;
break (open up)

When a junction opens, you have an immediate failure.
When a junction is weakened, the service life of the device is shortened. How much shorter the life is varies by how badly the junction was weakened, and how hard the junction works.

continued:

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by TheChas In reply to

Think of a semi-conductor junction as a balloon.
If you inflate the balloon to no larger than it's normal size, it can be inflated and deflated over and over.
However, each time you over-inflate the balloon, you stretch and weaken the balloon. Sometimes, you weaken the balloon to the point where it can pop even at less than normal inflation.

Protection:
The 'best' protection from surges is to unplug power cords, modem lines, and network cables.

After that, a high quality surge protector with phone-line and network protection will take care of normal surges.
Make sure that the ground line is properly connected and heavy enough all the way back to the external system ground rod at the electrical service entrance.
Surge protectors will NOT protect the PC if the ground line is not there, or has a high resistance.

Unfortunately, many UPS system do NOT include surge protection. When normal AC power is present, the UPS is little more than a battery charger for it's internal battery.
When the AC power drops out, the UPS switches on it's AC generator that is powered by the battery.

Chas

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by shantie In reply to

Hi thanks for the answer, you would not believe it,just about to toss it out, but next morning decided to give it another try, just with hard drive connected and it booted up. but each time I tried to connect second Master & Slave would not boot, I then tried a new connector ribbon to Secondary IDE but noticed the power switch connector is in the middle of the board right beside the Primary/Secondary connectors, so I tied all ribbons up away from the power switch, as thought they good be rubbing against the power and dislodging it, anyway computer has been working fine since I posted this question, all I did was used a new ribbon on Secondary drives and tied all the ribbons up away from the power switch, just shows you and I was about to toss it. But thanks for the surge information will keep that on record. Thank you Conchitta. Poster rated this answer.

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by shantie In reply to Power Surges

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