[Gllug] Swapping SW RAID 1 disks from PC to Sun

Christopher Hunter chrisehunter at blueyonder.co.uk
Sat Aug 14 10:10:24 UTC 2004

On Saturday 14 Aug 2004 9:46 am, Chris Bell wrote:
> On Fri 13 Aug, Nix wrote:
> > I had one as well: the surge protector blew, but it seems not fast
> > enough... :(
>    I purchased some red components that look like disc capacitors, normally
> high impedance but temporary short circuit with anything higher than peak
> mains volts, and I have placed three in L/N/E delta formation both before
> and after a fairly beefy common mode rejection filter. The majority of my
> hardware is fed through this device so that everything moves together.
>    Most of the mains feeders near here are underground, so are unlikely to
> be hit.

Most "lightning surges" are induced on to power lines, aerials, or telephone 
cables.  A direct hit is virtually impossible to protect against.  There 
isn't really any "surge protector" that is fast enough to catch lightning 
splats - most of the cheap ones use VDRs (voltage dependant resistors - the 
"capacitor-like" components you described).  The response time of a VDR is 
hopeless, measured in milliseconds, so they afford little protection, and 
often fail short circuit, leading to further damage.

The only component that's anywhere near fast enough is the Tritium-Filled Gas 
Discharge Tube, and these sometimes miss the front edge of a spike.  These 
used to be available (made by MO-Valve) from Farnell, but appear to have been 
discontinued (like many really useful components), as the price rose to 
almost £4 each.  These things looked like neons, and would catch very fast 

I had a fun-filled few days (back in the 80s) blowing up various pieces of 
telephone equipment in the High Voltage Lab at City University with simulated 
lightning strikes.  The only component that came close to being useful was 
the Tritium GDT, which would prevent destruction of the gear in about 60% of 
cases, but still would sometimes allow the fast edge of the spike through.

Your approach of earthing everything before it comes into your house is 
probably as good as you can achieve, but I'd had serious reservations about 
having an outdoor aerial connected in any way to a card in a computer that I 
cared about!

My setup has outdoor aerials, feeding tuners in a diecast case outside the 
house, which then provide optical fibre connection indoors, with another 
fibre being used for control from indoors.  

Paranoid about lightning?  No - I'm doing some designs of equipment suitable 
for use in the tropics for a manufacturer of home entertainment gear.  I've 
also had the experience of a lightning strike to a neighbour's house, which 
destroyed his living room by setting the TV on fire, and destroyed (by 
induction) my favourite shortwave receiver!


Gllug mailing list  -  Gllug at gllug.org.uk

More information about the GLLUG mailing list