hot tube chassis?

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<mikemt@localnet.com> 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."

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In article <1119559422.673001.234500@g44g2000cwa.googlegroups.com>,
<mikemt@localnet.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."

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On 23 Jun 2005 13:43:42 -0700, mikemt@localnet.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..
>
>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 dragonsclawJUNK@JUNKmindspring.com
, / / / Running United Devices "Cure For Cancer" Project 24/7 Have you helped? http://www.grid.org

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<mikemt@localnet.com> 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."