Conference hydra::amiga_v1

    Re .0:
    
    As the quoted note says, it is easy to provide surge protection on a
    "do-it-yourself" basis.  I suspect most people use a power strip
    anyway, so it's *definitely* worth one's while to open it up and
    install 3 MOVs across the two leads and protective ground. 
    
    If you buy a strip which claims to provide surge protection, you should
    check to see that it has all three MOVs.  Many of them use only one or
    two MOVs; some protection is better than none, but it's better to wear
    a belt *and* suspenders in this case.  You should also make sure that
    your outlet has a *real* ground, or you won't have any real protection. 
    
    Radio Shack #276-570 (Standard) is $1.59/ea.  #276-568 (Heavy-Duty)
    sells for $1.99/ea.  They're both cheap insurance. 

       I remember the article in BYTE, but being less than a visionary,
       through it out along with the issue.  With all the hardware I have
       plugged into my power bar (I take the North American power grid
       down a few notches everytime time I flip the switch), I would
       sleep alot better knowing that I was protected somewhat from the
       elements.
       
       Could someone with an understanding of Hots and Grounds, please
       draw up a quick schematic of the MOV placements for us (me?)
       non-technical types.
       
       Thanks in advance.
       
       Art
       

    Re .2:
    
    My artwork leaves something to be desired, but here goes...
    
    =========================+================+-------+
    "Hot"     (black wire)   :                |       :
                            MOV               |       :
                             :                |       :
    =========================+====== []   [] =+      MOV
    "Neutral" (white wire)   :                        :
                            MOV        (_)            :
                             :          |             :
    =========================+==========+-------------+
    "Ground"  (green wire)

    The point is that there are three wires (hot, neutral & ground)
    and that MOVs should be installed between each pair thereof.  In
    theory, the Neutral wire is at ground potential, but all bets are
    off during electrical storms and heavy load situations.
    
    When you do your connections, you may find it easiest to use any excess
    screw terminals you find on the outlets in your power strip.  The
    ground screw is supposed to be painted green for easy identification;
    the "hot" side of the outlet is metallic yellow, while the "neutral"
    side is metallic white.                

       Bill,
       
       Artwork is great - thanks!
       
       Art
       

Great!  I figured that someone here would understand this stuff.  Sounds like a
much better deal than $100 for a commercial unit.

Is there a right way and a wrong way to install a MOV?  (In other words, are the
two leads equivalent, or different like a diode?)  If the power strip is fused,
which side of the fuse should the MOVs go?

When you get done, how do you know if it really works?  And what are the
symptoms when a surge actually occurs?

Is there anything else you get in a high quality (expensive) power strip?  There
is mention in the original note of hash protection - is that RFI?  Is it
important to deal with it?

	Paul

    Re .5:
    
>   Is there a right way and a wrong way to install a MOV?  (In other
>   words, are the two leads equivalent, or different like a diode?)  If
>   the power strip is fused, which side of the fuse should the MOVs go?
    
    MOVs don't have polarity.  (We're dealing with AC here, right?)
    I'd put the MOVs after the circuit breaker/fuse only for the reason
    that I'd hope the MOV could overload same (before its own death)
    in the event that a sustained high voltage appeared on the line.
    
>   When you get done, how do you know if it really works?  And what are
>   the symptoms when a surge actually occurs? 
    
    I'm afraid you don't.  If you want to put a neon bulb in series
    with the MOV, it would light in the event the MOV passes a current.
    Without the MOV, the symptom of a power surge could well be the
    death of something inside your Amiga.
    
>   Is there anything else you get in a high quality (expensive) power
>   strip?  There is mention in the original note of hash protection - is
>   that RFI?  Is it important to deal with it? 
    
    Where an MOV presents a short circuit to short-term voltage spikes
    (diverting them through the "path of least resistance" to where they
    won't do any damage), other power defects can occur.  High frequency
    noise on the line won't be filtered off by the MOV, but could well find
    its way through the power supply to mess up the voltages inside your
    equipment.  RFI (Radio Frequency Interference) can have the effect of
    inserting signals into the circuitry, resulting in unpredictable
    results.  These filters are intended to cancel such noise before it
    reaches the power supply.  If you add such a filter, put it *after* the
    MOVs, so the amplitude is chopped before the filter gets it.

    What are the specs on the MOV's? Would two in parallel across each
    line be better? Could you simply install them at your fuse box?
    (It seems to me that if they are protecting your house from a shock
    coming in on the line, you might as well protect the whole house,
    right?
    
    dov

    I don't really need to know this to take advantage of all that's
    been said here, but could somebody please deacronymize (pardon my
    verbification) "MOV"?  Thanks,
    
    len.
    

    MOV's are specified as to the voltage they become conductive AND
    how many joules they will absorb like so 150{letter}10 = conducts
    at 150 volts and will withstand 10 joules (I don't know what the
    letter stands for).  We (DEC) make the H7007 series and they are
    quite good but too expensive for non-clients, so it is best to brew
    your own.  If you do deceide to make your own, make sure that the
    wires used are of heavy enough caliber (like 12 Ga.) AND make sure
    that the outlet used is PROPERLY GROUNDED.  This means NO ground
    wires separate from the phase and neutral wires, in fact the best
    thing you could do is to run a size 12 from the panel box to an
    outlet that has the MOV's mounted inside and plug your Amiga into
    that.  For people in heavy thunder storm areas, it is best to unplug
    the computer anyway, a first strike could take out the MOV's and
    then no protection is assured.
    
    Jean
    

    Re .7, .8:
    
    MOV = Metal Oxide Varistor.  Physically, the MOVs sold by Radio Shack
    look like disk capacitors.
    
    MOVs should be near the device being protected.  A nearby lightning
    strike could easily induce a substantial voltage in the wiring between
    the circuit breaker box and your system.  MOVs in the breaker box
    wouldn't help in such a case. 

    Re: .6

>   MOVs don't have polarity.  (We're dealing with AC here, right?)
>   I'd put the MOVs after the circuit breaker/fuse only for the reason
>   that I'd hope the MOV could overload same (before its own death)
>   in the event that a sustained high voltage appeared on the line.
    
    I don't follow you.  By "after the circuit breaker" do you mean between
    the circuit breaker and the wall, or between the circuit breaker and
    the amiga?  I can't tell if you are suggesting that the MOV will might
    protect the circuit breaker or visa versa.

    Re: .?

    I gather that when a MOV is overloaded it burns out and becomes a
    no-op.  Thus, you could take a power hit and blow the MOVs without
    knowing it.  Forever after you would have no protection and not know
    it.  Is this right?  The same could occur if you had a faulty MOV to
    start with.  Doesn't seem like very secure protection.

    I was totally lost on the discussion about having a 12ga line direct to
    the breaker box, and warnings about multiple grounds, etc.  Does this
    mean that MOVs in a power strip might not help depending on how the
    house wiring is configured?  Also, about using 12ga to wire in the
    MOVs:  are these not devices with leads of their own, like a resistor?
    If so, do they have 12ga leads?

    This is all very helpful, though the issues seem to be getting more
    complex rather than more clear.

	Paul

    Re .11:
    
    In .6 I was talking about where the MOVs should be relative to the
    circuit breaker/fuse *within a power strip*.  There's no compelling
    reason to put them either ahead or behind the breaker; I simply opted
    for placing them after same and speculated that under a sustained high
    voltage condition the MOV might draw enough current to trip the breaker
    (if it doesn't burn up first).
    
    In the event an MOV *does* take a big surge and dies, you won't know
    about it.  I'd hope this is a rare occurrence.  Some of the commercial
    products have an MOV status light (LED?) but I'm not sure how it's
    wired.  You're right; a dead MOV is a non-entity electrically.
    
    We've repeatedly talked about providing MOVs in a "delta" configuration
    -- which requires three MOVs and a good ground wire.  If the ground is
    inadequate, the two MOVs which connect to it don't provide any
    protection.  The National Electrical Code is pretty explicit about how
    grounding should be done.  My recommendation is DON'T CHEAT and you'll
    be just fine. 

    The idea behind 12 Ga wire is to provide a low impedence path to
    the breaker box and thus to the ground which should be connected
    to the neutral (in the box) and to a "good ground" (water pipe or
    rod driven in the ground).  Low impedence is further afforded by
    having the wires (phase neutral & ground) in a bundle, thus the
    magnetic field created by current flowing in one wire is cancelled
    by the return in the other wire, if the ground wire is separate
    from the current carrying conductors (phase & neutral) and a fault
    occurs, be it a spike or a malfunction, the wires become inductors
    and enough impedence is present in the wires to impair the performance
    of the MOV's.
    
    The way our H7007's are made is like so:
    
    ----------FUSE----MOV------
         |	    |
    	 -neon lamp--
    
    If the MOV shorts out, the fuse blows and the neon lamp lights.
    If the MOV opens, you won't know!  The installation requires that
    the thing be placed no more than 3 feet from the panel, if it placed
    further, less protection is afforded.
    
    I am running out of time and out of breath....
    
    Jean