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#1
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hot tube chassis?
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 |
#2
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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." |
#3
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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 |
#4
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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." |
#6
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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 - |
#8
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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 |
#9
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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." |
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