grounding questions...

[Tony Allgood]

Hi all,

NJ>Double-insulation adds an extra insulation layer between the mains
and the outside world, so no protective earth is required.

This is true, but for DIY use I would have thought for metal cases with
an internal power supply a earth is to be recommended. Most of the metal
clad two-wire mains stuff has an internal plastic chassis, hence the
double insulated label. Although, I think we can get away with the
double insulated criteria if we use a ready made wallwart for our diy
designs.

On the same point, some local councils require a 'PAT PASSED' sticker on
the back of all mains powered stuff. This is the safety test that all
(good) repair shops are required to do by law before passing the
reapired goods back to the customer. This can apply to the music
equipment of bands wanting to play at a public venue. The distinction
between class 1 and 2 on DIY stuff may be hard to explain.

However, you can buy PAT stickers from Farnell, Maplin etc. :-)

Interesting point about the tip of jack plug which is plugged into
anything mains powered... although the real problem comes from speaker
leads.

Regards,

Tony Allgood  Penrith, Cumbria, UK

Modular synth circuits, TB303 clone and Filter Rack

http://www.techrepairs.freeserve.co.uk/projects.htm