Lightning

I understand everything you have stated but I still think it falls short of explaining why the amplifier was damaged in such a specific manner. Absolutely nothing else connected to the stereo was electrically damaged in a similar manner. The only other damage incurred was to the antenna input stage of the tuner, which given the circumstances is intuitively explainable. The damage to the amplifier however was complete. Every component after the power transformer including the main filter capacitors were damaged.
I doubt the lightning path to ground could have occurred via the speaker wires through concrete as the amp has a timed speaker connect relay in the normally open position while off. There was also no damage to the speaker wire insulation, which I would have expected had such a path to ground occurred.
There is no doubt in my mind that a very strong and rapidly moving magnetic field was in the proximity of the amp as the (two) nearby televisions were magnetized as a result of the event. No other set in the house was affected. I personally wired the house and can state to a certainty that each of the damaged sets were on separate branch circuits on different levels of the house and that no other devices on either branch circuit were affected in any manner. The stereo was and still is on a dedicated circuit using 12-3 BX. Each of the four duplex outlets on that dedicated circuit have internal surge protectors, and their indicator lights still glow to this day indicating they were not "spent".
The roof antenna is FM only and is in no manner connected to the CATV, except for a singular 10 gauge wire from the coax grounding block to the ground buss in the main service panel. Each TV is connected to the CATV via starship pattern to a single 4 way splitter to the CATV. The CATV coax is also grounded to the main ground bar.
The only difference between the power amp and every other interconnected component in the dedicated stereo system is the size of the Power Amp's Power transformer. Much bigger than any other power transformer in the system. I don't think it is unreasonable to theorize that a current could have been induced into the coils of the transformer by a rapidly moving powerful magnetic field. I also believe Ohm's law can be applied in this situation as there was never a direct path to ground other than via the interconnects.

To summarize, it is my belief that a great voltage was induced into the primary or secondary side of the amp's power transformer, which simply went on to blow out the power supply of the amp thus causing a cascading failure to the remainder of the amp's internal circuitry. Why the power amp alone was singled out is beyond me. The only difference between it and the other five components (preamp-tuner-CDP-EQ-Tape Deck) connected at the time was the size of the amplifier's power transformer.

Insufficient information exists. For example, normal is for a surge be incoming to many adjacent appliances. But only cause damage in one. The surge is incoming to everything but only does damage in one or a few parts inside one appliance. Yes, it may pass through maybe 15 parts. But only the weakest part fails.

Relays open or closed are a conductive path to any surge. A common path through a relay is from its coil to its wiper contacts. Open that relay and find no indication. Normal is for destructive currents to pass through most items without any indication. Even open relays.

A surge can also connect to concrete via the wire and not leave any indication on wire insulation. Observation alone is one reason why many never understand how a surge does damage.

Demonstrated by the IBM PC and so many other engineering examples is the near zero damage created by fields. The resulting energy is big time too small. A nearby strike only ten feet from a radio antenna can create thousands of voltage on that antenna's lead. And an NE-2 neon glow lamp (less than a milliamp) attached to that lead then converts thousand of volts to tens of volts. Near zero. Because fields create a high voltage with near zero current. Nowhere near sufficient energy to create damage as described.

Lightning can also create other conductive paths causing much higher energy from AC electric to then create a follow through current. That follow through current is one reason for more serious damage. And an example of why damage is traceable to a human mistake that let a surge inside the building.

To have that damage means a current had to be incoming on one path and outgoing on another. Routine is to have a surge incoming to every appliance in the house. But only one appliance is damaged - ie the amp. Because that one appliance made a best connection to earth. Because that one appliance acted like a surge protector for everything else - the preamp, tuner, tape deck, refrigerator, answering machine, computer, bathroom GFCI, mobile phone on a charger, and even smoke detectors.

Damage always means a current that was incoming on one path while simultaneously outgoing on some other path to earth. Damage that exists only because the surge was not earthed BEFORE entering the building. And that is a common human mistake. To not earth every incoming wire either by hardwire or via a protector.

Too many possible and unreported paths can exist. But we know this from well understood energy numbers and over 100 years of experience. Fields do not and cannot cause damage you have described. And you do not know all the many and possible paths and electrical conductors that exist from the appliance to earth. A surge can even pass through wire insulation without leaving any indication.

You have wires entering the building without first connecting to single point earth ground. Not safety ground. For many electrical reasons, safety ground and earth ground are different. Even when interconnected. Even wire length (ie 'more than 10 feet') makes the two grounds electrically different. TV cable connected to safety ground bus bar in a breaker box) means it is not properly earthed for electronics protection.

Adjacent surge protectors never indicate 'spent'. That light only reports when a protector was so grossly undersized as to disconnect internal parts as fast as possible. To otherwise avert a house fire. Nothing on those protectors report 'spent' - also called degradation. The light only reports when a protector was grossly undersized and was a threat to human life.

View how a protector is wired. Surges at thousands of volts can pass through those protectors. And only create tens of volt differences across the protector parts. An example of relevant electrical concepts that cause many to ignore significant details. You have assumed protector lights report things that those lights can never report. A protector could be completely degraded. But its light will still report good. Light can only report one type of failure.

Without actual inspection and other details, nobody can say exactly how a surge found earth. But this much is obvious. You did not have properly earth protection on every incoming wire. Somehow a surge current was all but invited inside where it found a destructive path to earth. Damage, as described, can only occur from something with higher energy. Induced fields can never create that damage. Otherwise every RF amplifier in every radio (something far more sensitive) is destroyed.

Very impressive description, thank you. What else can I say, lightning struck while I was home. As the days passed I noticed more and more appliances had failed until I realized there was a common event. To collect from my insurance company each failed component was checked out by a technician who provided a notarized affidavit stating that the damage was indeed lightning caused.

The one thing everyone stressed is that lightning does what it wants, engineering logic be damned.

So the issue will remain unsatisfactorily explained to me while you are certain that my house was insufficiently earth grounded as a surge current found it's way to one appliance that wasn't even switched on. The fact that no other components, devices or even a single light bulb was damaged is a testament to their resilience I suppose.

Thank you.

Insufficient information exists. For example, normal is for a surge be incoming to many adjacent appliances. But only cause damage in one. The surge is incoming to everything but only does damage in one or a few parts inside one appliance. Yes, it may pass through maybe 15 parts. But only the weakest part fails.

Relays open or closed are a conductive path to any surge. A common path through a relay is from its coil to its wiper contacts. Open that relay and find no indication. Normal is for destructive currents to pass through most items without any indication. Even open relays.

A surge can also connect to concrete via the wire and not leave any indication on wire insulation. Observation alone is one reason why many never understand how a surge does damage.

Demonstrated by the IBM PC and so many other engineering examples is the near zero damage created by fields. The resulting energy is big time too small. A nearby strike only ten feet from a radio antenna can create thousands of voltage on that antenna's lead. And an NE-2 neon glow lamp (less than a milliamp) attached to that lead then converts thousand of volts to tens of volts. Near zero. Because fields create a high voltage with near zero current. Nowhere near sufficient energy to create damage as described.

Lightning can also create other conductive paths causing much higher energy from AC electric to then create a follow through current. That follow through current is one reason for more serious damage. And an example of why damage is traceable to a human mistake that let a surge inside the building.

To have that damage means a current had to be incoming on one path and outgoing on another. Routine is to have a surge incoming to every appliance in the house. But only one appliance is damaged - ie the amp. Because that one appliance made a best connection to earth. Because that one appliance acted like a surge protector for everything else - the preamp, tuner, tape deck, refrigerator, answering machine, computer, bathroom GFCI, mobile phone on a charger, and even smoke detectors.

Damage always means a current that was incoming on one path while simultaneously outgoing on some other path to earth. Damage that exists only because the surge was not earthed BEFORE entering the building. And that is a common human mistake. To not earth every incoming wire either by hardwire or via a protector.

Too many possible and unreported paths can exist. But we know this from well understood energy numbers and over 100 years of experience. Fields do not and cannot cause damage you have described. And you do not know all the many and possible paths and electrical conductors that exist from the appliance to earth. A surge can even pass through wire insulation without leaving any indication.

You have wires entering the building without first connecting to single point earth ground. Not safety ground. For many electrical reasons, safety ground and earth ground are different. Even when interconnected. Even wire length (ie 'more than 10 feet') makes the two grounds electrically different. TV cable connected to safety ground bus bar in a breaker box) means it is not properly earthed for electronics protection.

Adjacent surge protectors never indicate 'spent'. That light only reports when a protector was so grossly undersized as to disconnect internal parts as fast as possible. To otherwise avert a house fire. Nothing on those protectors report 'spent' - also called degradation. The light only reports when a protector was grossly undersized and was a threat to human life.

View how a protector is wired. Surges at thousands of volts can pass through those protectors. And only create tens of volt differences across the protector parts. An example of relevant electrical concepts that cause many to ignore significant details. You have assumed protector lights report things that those lights can never report. A protector could be completely degraded. But its light will still report good. Light can only report one type of failure.

Without actual inspection and other details, nobody can say exactly how a surge found earth. But this much is obvious. You did not have properly earth protection on every incoming wire. Somehow a surge current was all but invited inside where it found a destructive path to earth. Damage, as described, can only occur from something with higher energy. Induced fields can never create that damage. Otherwise every RF amplifier in every radio (something far more sensitive) is destroyed.

Wow, I didn't realize there was so many audiophiles that know
this much about lightning strikes. Even the people that make a
living studying lightning could learn something here.

I can honestly say when it rains it pours. As if it wasn't
enough to lose a job, you get struck down by one of nature's
most fierce weather conditions. I lost a transformer in an amp
one time due to lightning, it was repairable though.