does anybody out there know how the old tube chassis on radios, amps,
and tv's were always grounded hot from one side of the power cord. well
my question is were the printed circuit tube chassis grounded like this
too?

thanks, mike

wrote:
does anybody out there know how the old tube chassis on radios, amps,
and tv's were always grounded hot from one side of the power cord. well
my question is were the printed circuit tube chassis grounded like this
too?

Many were. Some had the metal case floating, or tied to one side of
the line through a .1 uF ceramic cap for shielding. Why?

If it doesn't have a power transformer, adding an isolation transformer
is always the safe thing to do.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

thanks scott. It was an old emerson phono amp and I was thinking about
making a guitar amp out of it.. i looked at it again and i didn't see
the metal casing on it being tied to one side line with a cap so now im
starting to think it wasnt grounded to one side of the line..

thanks, mike

In article .com,
wrote:
thanks scott. It was an old emerson phono amp and I was thinking about
making a guitar amp out of it.. i looked at it again and i didn't see
the metal casing on it being tied to one side line with a cap so now im
starting to think it wasnt grounded to one side of the line..

It may not be. You sure it doesn't have a power transformer?

Get the Sam's Photofact on it and see.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

In article .com writes:

It was an old emerson phono amp and I was thinking about
making a guitar amp out of it.

You're no Les Paul, and there's no need to do this today. Besides, you
might find it to be a shocking experience.


--
I'm really Mike Rivers )
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me he double-m-eleven-double-zero at yahoo

Many were. Some had the metal case floating, or tied to one side of
the line through a .1 uF ceramic cap for shielding. Why?

My Crosley had this configuration too. It was common in the mid 1950s: 35W4
rectifier, 50C5 power output, 12BA6 IF, 12BE6 mixer/local oscillator, and a
12AV6 dual diode + triode. Filaments wired in series are tied to 117vac
line. Rectifier puts out about 165vdc. Chassis is 'hot' if the plug is in
the wall socket backwards. Makes for a nasty shock. Don't use one in the
bathtub!


--
Best Regards,

Mark A. Weiss, P.E.
www.mwcomms.com
-

On 23 Jun 2005 13:43:42 -0700, wrote:

thanks scott. It was an old emerson phono amp and I was thinking about
making a guitar amp out of it.. i looked at it again and i didn't see
the metal casing on it being tied to one side line with a cap so now im
starting to think it wasnt grounded to one side of the line..

thanks, mike
SERIOUSLY *NOT* recommended for Guitar use.
Managing Polarised power is very shaky with unknown extension cords/
power strips.
How many cords have YOU seen with the 3rd prong missing?
How many times have you seen a 3 prong plug inserted into a cheepie 2
prong extension cord?
Every one of thos, is a time for the leads to get flipped and have a
hot shield lead connected to the pickup.
Proper amps have a power transformer to isolate the MAINS FROM THE b+
AND CHASSIS.

, _
, | \ MKA: Steve Urbach
, | )erek No JUNK in my email please
, ____|_/ragonsclaw
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org

yeah I had a Zenith H615 and i was at the pool and i have a metal deck.
I moved the radio, my arm was touching the deck and i just hit the
chssis with my hand. that fuse blew thank god or I would have been
dead. that schock went threw my arm and out the other and down my
legs.. ohh and i was in my bare feet standing on cement.. im lucky im
not dead!!!!

and scott.. no it doesnt have a power transformer just two out put
transformers for stereo.. it has these tubes, 6be6, 6ba6, 12ax7, and
two 25eh5's.

thank you

mike

wrote:
yeah I had a Zenith H615 and i was at the pool and i have a metal deck.
I moved the radio, my arm was touching the deck and i just hit the
chssis with my hand. that fuse blew thank god or I would have been
dead. that schock went threw my arm and out the other and down my
legs.. ohh and i was in my bare feet standing on cement.. im lucky im
not dead!!!!

and scott.. no it doesnt have a power transformer just two out put
transformers for stereo.. it has these tubes, 6be6, 6ba6, 12ax7, and
two 25eh5's.

The 25EH5s are a dead giveaway of a series filament string, and a good
sign of a hot chassis design.

An isolation transformer will be twenty or thirty bucks and adding it
is no big deal.

Note that if the amp is normally intended to work with an old ceramic
phono cartridge, it may not have anywhere near enough gain for a guitar.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."