Turn it off is the surest thing to do -- leave it on and you're inviting disaster (or an upgrade to your gear).
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You would need to unplug the system in order to avoid lightening damage.
I'm no expert on electrical systems or lightening suppression, but I would think the most logical approach is a whole house surge suppressor installed at the meter by your power provider. That's what I'm going to do when we build our new house.
the lightning often travels via the neutral or ground (the two are usually connected at the panel). When you throw the switch, you disconnect the line or hot leg and not the neutral or ground. If you unplug, you disconnect all three. Likewise, lightning can travel through your phone or computer lines as well.
All the above is great advice. Also, the satellite dishes can carry spikes and lightning into your receiver, as can FM antennae. I am having an electrician install ground wires and rods for my dishes and antennae, and I unplug the things I don't want destroyed. Even small static discharges can harm delicate electronics.
Grounding antena won't protect from direct hit (even ground rod is problematic). The real purpose for grounding antena is to prevent static electricity build-up caused by the wind that can charge your antena to several kV making it electrically the "tallest" structure in the area. Size of the grounding wire does not matter.
Always unplug to prevent ground differentials.
It is true that the grounding rod only prevents the static discharge issue. Also, it probably protects you from your insurance company if they claim that your negligence of putting up an antenna caused lightning to strike your house. A direct hit will take everything out. A neighbor had his house burn down when the lightning strike fused the circuit breaker box and the wiring fried through the walls and the house was fully involved. lesson? unplug everything, and insure it!
Direct lightning creates plasma about 1 foot in diameter and there is no wire in the world to bring it to ground, but if it gets one of the smaller "branches" it might protect as long as wire is thick and does not have sharp angles (short time = high frequency). I have tall street lamps around my house working as grounding rods. Not grounded antena migh appear taller than street lights (or trees).
Kijanki, your comment about the plasma ball reminds me of a time I was driving in Tennessee during a thunder storm. I was approaching a corner and witnessed a lightning bolt strike a tree. It was probably 40 yards ahead of me. What I saw was a big orange ball engulf the base of the tree when the lightning struck. It was a truly awesome sight.
Current will find all possible paths to ground even if your tuner provides easy one. When the rest of equipment is unplugged and well isolated from the ground current won't flow thru it but will flow thru center wire of your interconnect to input of an amp and back (high voltage will destroy/short input) thru interconnects ground to tuner and earth ground. This is not very "efficient path" but your amp's input doesn't need much to get damaged. Unplug everything.
My house took a bad lightning hit on 7/5/06- I'll never forget it. Totally destroyed the hot tub. It damaged a lot of electrical gear in the house too. I had surge protectors on my gear- Stereo, TV, Home theatre, and PC but everything with a three prong plug was damaged. The TV's and equipment that had two prong plugs were fine. The new hot tub has it's own ground rod now. btw- the large oak tree next to the house that provided the path in for the lightning (I was on the back porch and saw the lightning hit) was removed and we have had no more issues.
I would at least turn the system off. A surge from a lightning strike hit my stereo in the 80s and mess up several compenents - Teac tape deck, Yamaha preamp. They were never right again after that although I sent them back for repair several times. Surge protectors may have improved but they always have a lag before the protection kicks in. When a storm comes be very careful IME.
The only time I saw damage from lightning was a couple decades ago. Computer terminals connected by hardwire to servers were getting destroyed following lighting storms. The hardwire data connections were the path for the induced potentials. We specified inexpensive lightning protection devices on the data lines ( they were around $50 per unit) and never lost another terminal. It has been a while and I cannot recall the name of the company. However we went for the fastest protection, the down side was that the fastest protective devices gave up the ghost in doing their duty, which a few did. But at that time a computer monitor was going for $500 so the $50 loss was acceptable. Lightning usually gets coupled via a path other than the power lines, i.e. a cable, antenna, etc. But it certainly can come in via the power lines. Suggestion is to find a device that does nothing but protect against lightning, whose primary selling point is speed, and that is not designed specifically for audio equipment. In general you will get a better product of that type by staying with industry standards for protection of data equipment. Try any large company that sells markets the protection for computer systems. Preferably one that can be purchased either direct or through one of the large electronics distribution houses. I am a little suspect of the stuff designed specifically for high end audio and sold by high end audio marketing - just too small of a market and too riddled with overpriced gimmicks. If the industrial quality products don't do what they promise, the companies don't last long, so their is a little more assurance of the quality of product if the manufacturer has been at it a while and has a business clientele.
Tonywinsc - your damage of three prong devices suggest that lightning hiting tree/ground near the house creates big voltage differential between earth ground and neutral wires. Switching off equipment would not help since switch is on the hot wire. Recently I looked at power strips in Tiger.com store and the most expensive one not only had the most of Joules but also different split betweens tree lines. It had acually less Joules than cheaper one on the hot wire and much more between ground and neutral.
I have Monster Power Surge Protectors on both the HT system and Stereo system. So they apparently do not protect the earth ground. But Monster Power made good on the damages- no fuss. Other items, such as PC with 3 prong plug took a hit with basic surge protection and our electric blanket (3 prong) but the TV's were ok- two prong plugs.
Picking this thread up late, but still very relevant discussion. I thought my "high quality" AC line surge protector would do the job, but I'm glad I read the posts. Emailists is right about cable TV lines. My area is served by Comcast and I'm pretty sure the cable is above ground. I guess the problem is that a lightning strike could work its way through the cable, into my TV, and then into my preamp, into the amp to ground!! Yikes, the best line surge protector in the world won't help me in the event that scenario occurred.
Aren't there surge protectors out there that can also protect above ground cable TV inputs? And BTW, if a lightning strike came in through cable, a PurePower AC regenerator will not help!!
If I understand the science correctly, then the best advice is to disconnect the AC mains and TV cable, if the latter is from an above ground network. Does the forum concur?
I was in Palm Springs CA. a few summers ago doing some house sitting. A rare summer storm blew thru. At least 3 or 4 lightning strikes within a couple blocks. It rained like no tomorrow for about 2 hours.....than on to hot and humid
The MODEM on the computer was dead.
Everything else was OK.
My house took a near hit many years ago. I remember seeing the entire street light up and hearing the boom.. Not really sure where the bolt landed, but it caused much damage, and my system wasn't even on. The input section of my tuner was blown to bits, literally, according to my technician. Possibly the bolt hit my antenna and came in, even though the mast was connected to an 8 foot copper ground rod. The antenna (yagi) was connected to a 300 to 75 ohm balun transformer to a grounding block onto my tuner. I never checked the condition of the balun or antenna, I was told to replace them both as they were probably fried.
The worst damage was to my power amp, an Apt A-1. It was plugged into the switched outlet of my Hapi 2 preamp, which was off. Two days after the strike, I switched on my system and was treated to some real fireworks. It looked like a sparkler was burning inside the Apt. I quickly unhooked it and ran it outside because it looked like it might set my house on fire. The technician who repaired it said every component except for the signal lights were ruined.
So how did this happen? It was theorized that the rapid and very powerful electric field induced a high current in the power transformer, which then cascaded throughout the rest of the amp. I'll never really know.
What I do know however, is that lightning does whatever it wants and that I was very thankful to have "replacement value" on my homeowners insurance. That's how I got my Aragon 2004. I believe most power conditioners come with equipment protection policies, but I don't know if they cover lightning.
In addition to the tuner and amp, my telephones were reprogrammed and my TVs were all magnetized to one color. The preamp was the only component in my house to come through unscathed.
I'll add as I lived for years in a odd location with crazy lightning issues. unplug anything you dont want fried. Direct hits can and will take out anything no matter if a protector is hooked up. near strike may but not as likely. near strikes can easily take out phones and modems. Also I have seen instruments unplugged and still get wasted. Neighbors phone answering machine took a hit with the plug on the counter a foot away from the outlet. In general phone/answering machines/ modems go first and real easily. other stuff harder. Unplug. BTW have seen results of lightning going through open window so close the windows to be safe. Saw the mention about copper rod in ground. We had to have four holes drilled a couple hundred feet deep at building corners and rods inserted surrounded by some sort of salt compound to complete make the building lightning safe. been in it for a couple hits (maybe 50? with no issues.) unplug always.