[Elecraft] [K3] KIO3 failure mode

[Jim Brown]

On 8/23/2022 2:47 PM, David Gilbert wrote:
> If I remember correctly, the laptop power supply was even plugged into a 
> quality surge protected UPS.

MOV Surge protectors short the phase and neutral conductors to the green 
wire in the event of a surge. In the event of a strike, the IR drop in 
the green wire raises the potential of the computer. It's common for the 
potential difference between the computer and the chassis of anything to 
which it's connected to fry either or both units. This is why MOV surge 
protectors are a bad idea -- in systems where interconnected components 
are powered from MOVs at different outlets, or to equipment that's 
grounded, they are as likely to CAUSE destructive failures as to protect 
anything.

We learned about this in the world of large sound systems more than 
twenty years ago, started using series-mode surge protectors, which 
store the surge in a very large inductor, then discharge it slowly. A 
company called SurgeX, for whom I did some tech writing and teaching at 
trade shows, licensed the patent for the pro audio market; two other 
companies licensed it for the computer world and home entertainment 
world respectively.

73, Jim K9YC