[NTLUG:Discuss] OT: Hz

[Steve Baker]

Patrick R. Michaud wrote:
> On Tue, Oct 18, 2011 at 12:34:15PM -0500, Fred James wrote:
>> It would seem logical that since no circuit board is likely to run
>> on household current directly, there must be a transformer of some
>> sort in the mix.  Might it be reasonable to assume that the
>> resulting voltage applied to the circuit board(s) could vary,
>> possibly considerably?
>
> Rusty already provided an excellent reply; here's my additional $0.02.
>
> Voltages on the AC lines already vary a fair bit over time
> and always have.  For example, earlier today I measured the
> voltage on one of my outlets at 124.7 volts; right now it's
> showing 123.9 volts.  Such variation is normal and expected.
> As long as the voltage is somewhere in the vicinity of 110 volts
> I think any modern appliance ought to be able to handle it.

...and the amount of voltage shift that this frequency variation can
possibly cause is vastly, VASTLY smaller than this natural voltage
variation.

> If you're seeing problems with multiple appliances, perhaps
> there's a fault somewhere in the household wiring itself
> or one of the other appliances connected to the circuits?

Certainly I'd try turning off (and preferably unplugging) one major
appliance at a time and seeing if this helps the problem.  Fridges,
freezers and airconditioners are all likely culprits because they switch
on and off at random times with the thermostat - and they consume lots of
power.  Switching something big on or off does induce significant spikes
in household circuits - and in extreme cases, that may be enough to
overwhelm the voltage regulators for some devices.

You might also consider a surge-protector (those are cheap) or even a
battery-backup UPS (Uninterruptable Power Supply) (not so cheap!) for your
own peace of mind.

Other problems that you might see are:

GROUND LOOPS:  Make sure that all of the bits of your computer (monitor,
keyboard, speaker amplifiers, tower, etc) are plugged into nearby outlets
- or (better still) the same extension cord.  Never plug the monitor into
an outlet (say) 10 feet from the computer.

FAULTY GROUND:  If your wall socket has a faulty ground - you might not
immediately notice it (ie everything seems to work OK) - but it's both
dangerous and prone to causing these kinds of problem.  You can buy
testers that you plug into the wall to check for this.  It's worth
buying/borrowing one to check out your outlets just for peace of mind. 
Over the last three places I've lived, I've found a total of four bad
ground wires!  One of those was in a brand new house just hours after the
property inspector had been out there inspecting them!

OVERLOADED OUTLETS:  Too many things plugged into one outlet via extension
cords and multi-way adapters.

 -- Steve