On Sun, 03 Aug 2014 19:16:08 +0100, Dave Plowman (News) wrote:


I'm talking about many years ago. There was plenty of gear around with
metal parts - even cases - and no earth.

If a case is properly earthed the worst case fault will simply blow a
fuse. Assuming the cabling feeding the device is heavy enough. And you
couldn't even guarantee that once.


A lot of live chassis stuff appeared over here while some areas still had
DC mains. I worked (well, messed about with!) quite a few old AC/DC
radios as a lad. I think there was also quite a bit of that stuff
produced during WWII, when it was very difficult for anything other than
the war effort to get metal for transformers.

There are certainly one or two circuits on the web for cheap guitar amps
that are live chassis.
Kay 703: http://www.freeinfosociety.com/elect...ematics/audio/
kay703.pdf
Harmony H400: http://www.angelfire.com/vt/audio/harmonyh400sch.jpg
I doubt if either of these would have been sold in the UK though.

"mick"


There are certainly one or two circuits on the web for cheap guitar amps
that are live chassis.
Kay 703: http://www.freeinfosociety.com/elect...ematics/audio/
kay703.pdf
Harmony H400: http://www.angelfire.com/vt/audio/harmonyh400sch.jpg

** Neither of the above are really *live* chassis - notice there is a RC
network in series with the chassis that has an impedance of well over
50kohms at 60Hz.

I know of NO guitar amp that ever was live chassis - cos it would be a
killer.


I doubt if either of these would have been sold in the UK though.

** Also they can only work with 117V mains unless a step-down tranny is
fitted inside.

All such amps were very low powered, mainly used as practise amps by
beginners.


..... Phil