[net.audio] Protect Your Stuff from Power Line Spikes

wjm@whuxk.UUCP (10/18/83)

There is a very simple way to protect yourself from power line voltage spikes.
You install a transient supressor (for all you fellow EE's out there on the net
it consists of some metal-oxide varistors connected between the "hot" side of
the line and ground).  A bonus is that it will also give your equipment some
protection against lightning strikes on or near the power line, but it is NOT
a substitute for proper lightning protection installed on any outdoor FM or TV
antennae.  There are two ways to do this:
1. If you want to protect your entire house, GE makes one that you can wire into
your circuit breaker box (local codes permitting, else you'll have to get an
licensed electrician to do it).  You just connect the two black wires to the
two "hot" wires coming into to the box on the "load" side of the main breaker
SAFETY NOTE - BE SURE TO TURN OFF THE MAIN BREAKER OR MAIN SWITCH BEFORE DOING
ANY WORK IN THE MAIN PANEL BOX AND KEEP YOUR FINGERS, TOOLS, ETC AWAY FROM THE
HOT CONTACTS ON THE "LINE" SIDE OF THE MAIN BREAKER OR SWITCH.
and the green wire to the ground connection in the box.
2. If you live in an apartment, or don't feel comfortable mucking around in the
panel box (and don't feel like getting an electrician in to do it for you),
Radio Shack makes a plug-in version that you can plug into any GROUNDED
(3 prong) wall receptacle. You plug the transient suppressor into the receptacle
and they plug your equipment into it.  It works quite well - I've been using one
for several years now.  They're also quite reasonably priced - around $12.00 or
so.
Bill Mitchell
Bell Laboratories
Whippany, NJ
(whuxk!wjm)

wjm@whuxk.UUCP (10/19/83)

One additional point about power line spike protection  that rabbit!jj
reminded me about (thankx).  Be sure to use devices that are UL approved (or
CSA approved if you are a Canadian reader of the net).  Both the GE and Radio
Shack devices I mentioned in my original article have UL approval (and I think
CSA approval as well but check for yourself to be sure).  For safety, it is
essential to only use approved devices in any electrical system, and the
National Electrical Code (as well as many local codes) requires that devices
be listed (approved) by a recognized testing laboratory (generally this is UL)
for the purpose that they will be used for.
While we're on the subject, one should check new audio equipment that one
is purchasing for UL, CSA, or equivalent (such as the German VDE) approval,
since this tells you that the gear passed safety checks for shock and fire
hazards before it left the factory and provides some protection for you and
anyone else near your equipment.
Also, be sure to check your equipment for leakage current after doing any
repairs on it - and make sure the technician checks it for safety after
it is repaired in the shop.  If you don't know how to do a leakage check,
DON'T fix your own stuff until you learn how - Its a very simple procedure
and is outlined in many books on audio and TV repair and only requires a
reasonably high impedance AC voltmeter and some small components.
Bill Mitchell
Bell Laboratories
Whippany, NJ  (whuxk!wjm)