Mark Oppat wrote:

John,
I stand my "ground" here. "Ground" IS INDEED "earth", one is the USA term,
one is used in the UK and elsewhere most often. However, in antique
radios we should use the term "CHASSIS" if that is what you are tying onto,
or "B-", also called "Common Negative, or Common neg" when you are tying to
that.

I'd be careful with "B-" as that's sometimes not circuit common
(return) -esp. with output tubes needing a negative bias. Chassis is
also dangerous because most AA5s use an isolated circuit common - with
the only (active) parts tied to chassis being the tuning cap (and
sometimes associated trimmers) - which are RF coupled to circuit common
through a cap. Though line AC can couple "backwards" through those caps
- (if they aren't leaking) - their small value should limit any shock
current to "tingle" level. The last thing you'd want someone to do is
tie a typical AA5 common to the chassis... Yes I know - some are anyway
- but they *should* be isolated from the user by design - where a
floating AA5 isn't.

Just my .02
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com

My post was intentionally mentioning that "B-" or "common neg" are NOT
necessarily "Chassis"... they are separate terms... sorry if that wasn't
clear.

Mark Oppat



"Randy or Sherry Guttery" wrote in message
. ..
Mark Oppat wrote:

John,
I stand my "ground" here. "Ground" IS INDEED "earth", one is the USA
term, one is used in the UK and elsewhere most often. However, in
antique radios we should use the term "CHASSIS" if that is what you are
tying onto, or "B-", also called "Common Negative, or Common neg" when
you are tying to that.

I'd be careful with "B-" as that's sometimes not circuit common
(return) -esp. with output tubes needing a negative bias. Chassis is also
dangerous because most AA5s use an isolated circuit common - with the only
(active) parts tied to chassis being the tuning cap (and sometimes
associated trimmers) - which are RF coupled to circuit common through a
cap. Though line AC can couple "backwards" through those caps - (if they
aren't leaking) - their small value should limit any shock current to
"tingle" level. The last thing you'd want someone to do is tie a typical
AA5 common to the chassis... Yes I know - some are anyway - but they
*should* be isolated from the user by design - where a floating AA5 isn't.

Just my .02
--
randy guttery

A Tender Tale - a page dedicated to those Ships and Crews
so vital to the United States Silent Service:
http://tendertale.com