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Re: Hot Chassis Wonder

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  • Hue Miller
    I was looking at a booklet for another educational kit the Progessive Radio Edu-Kit . This kit using octal vacuum tubes was sold from about 1947 to the mid
    Message 1 of 10 , Sep 1, 2010
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      I was looking at a booklet for another "educational kit" the "Progessive Radio Edu-Kit". This kit using
      octal vacuum tubes was sold from about 1947 to the mid 1980s with EXACTLY the same
      advertisement. In fact I wrote a magazine in the 1980s to ask if they thought that, as the Edu-Kit
      ad prophesized, transistors and printed circuits would really catch on. The magazine replied that
      yes, the advertising looked old-fashioned, but they always paid their bill. The projects in the
      booklet are mostly variations on grid leak detector, like "grid leak detector", "grid leak detector
      with one amplifier tube", "grid leak detector with 2 amplifier stages", etc. etc.
      Anyway, I see that one wire of the unpolarized power plug goes right to the chassis. Mama
      mia, that could be educational! The instructions do state to not touch anygrounded metal
      while touching this radio kit, and do not stand on a concrete floor. How could they sell this
      into the 1980s, I wonder??? -Hue Miller

      [Non-text portions of this message have been removed]
    • Leonard Meek
      I remember those days. We were always cautioned, if you get shocked, turn the plug around. People didn t seem to take getting shocked too sertously. ...
      Message 2 of 10 , Sep 1, 2010
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        I remember those days. We were always cautioned, "if you get shocked, turn
        the plug around." People didn't seem to take getting shocked too sertously.

        ----- Original Message -----
        From: "Hue Miller" <kargo_cult@...>
        To: <regenrx@yahoogroups.com>; <tetrode@...>
        Sent: Tuesday, August 31, 2010 10:03 PM
        Subject: [regenrx] Re: Hot Chassis Wonder


        >I was looking at a booklet for another "educational kit" the "Progessive
        >Radio Edu-Kit". This kit using
        > octal vacuum tubes was sold from about 1947 to the mid 1980s with EXACTLY
        > the same
        > advertisement. In fact I wrote a magazine in the 1980s to ask if they
        > thought that, as the Edu-Kit
        > ad prophesized, transistors and printed circuits would really catch on.
        > The magazine replied that
        > yes, the advertising looked old-fashioned, but they always paid their
        > bill. The projects in the
        > booklet are mostly variations on grid leak detector, like "grid leak
        > detector", "grid leak detector
        > with one amplifier tube", "grid leak detector with 2 amplifier stages",
        > etc. etc.
        > Anyway, I see that one wire of the unpolarized power plug goes right to
        > the chassis. Mama
        > mia, that could be educational! The instructions do state to not touch
        > anygrounded metal
        > while touching this radio kit, and do not stand on a concrete floor. How
        > could they sell this
        > into the 1980s, I wonder??? -Hue Miller
        >
        > [Non-text portions of this message have been removed]
        >
        >
        >
        > ------------------------------------
        >
        > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo!
        > Groups Links
        >
        >
        >
        >
      • dr_telecom
        Most of the kits in the 50s and early sixties had no power transformers. The Space Spanner, if I recall right, had a floating ground, but it was connected with
        Message 3 of 10 , Sep 1, 2010
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          Most of the kits in the 50s and early sixties had no power transformers.

          The Space Spanner, if I recall right, had a floating ground, but it was connected with a resistor and parallel cap to the 'chassis' and you could get a shock from it.

          Radios like the Hallicrafters S-38 series were a/c dc sets with hot chassis. The case was not tied to the chassis - you had bushings that kept them separate...but the bushings wear out over time, so beware. Just don't touch the screw in the knob and ground at the same time.

          if you use these old radios, use an isolation transformer! Heathkit made a nice one, and not only that, you can lower the line voltage a bit ...the old radios were designed for 110v ac, and my line voltage here is near 127v most of the time, or more than 10% high...stressing the parts in the radio. If you have an old transformer operated radio....it will be running with voltages on the high side, filament voltages on the high side, and more heat in the case.

          Heahtkit was one of the few to put a power transformer in almost every piece of gear they sold.

          THe Knight Span master (top of the line) had a power transformer. 6BZ6 and 6AW8A tube and selenium rectifier. The Space Spanner did not - 12AT7, 50C5, 35W4, and dropping resistor for filaments.

          Haven't gotten to the Ocean Hopper yet, but think it is 12AT6, 50C5 and 35W4 type line up and dropping resistor, no power transformer.

          Many early sets (30s and 40s) had a line cord with built in dropping resistor. They are real hazards now and most are bad.......

          All the A/C sets have live chassis, or ones separated by some caps...which will give yo a shock if you touch the chassis , screw on a knob(if there is one) etc......

          There weren't even polarized two pin plugs back then, and certainly no 3 wire cords with 3 pins.

          Some of the solid state stuff still has hot chassis.....cheap radios...use a dropping capacitor off the line....no power xfrm.....but it is PC board, and plastic push on knobs so you have to try to hard to get your fingers where you can shocked.

          Bob, drT in Plano, TX
        • Robert Bennett
          About 50 years ago, when I was 12/13 years old, I was playing around with our old live chassis domestic radio. I discovered that by connecting an earth wire
          Message 4 of 10 , Sep 1, 2010
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            About 50 years ago, when I was 12/13 years old, I was playing around with
            our old live chassis domestic radio.

            I discovered that by connecting an earth wire (which consisted of a length
            bare copper braid attached to a copper pipe in the ground), to the chassis
            of the radio, the short wave reception improved.

            In a moment of absentmindedness and with the radio powered on, I
            disconnected the earth by grabbing hold of the copper braid with both hands
            and pulling the connection apart.

            I received 230 volts across my body from one hand to the other.

            It was an experience which I was very lucky to survive and for the past 50
            years up to the present day, I am still frightened to work on line powered
            equipment.

            Don't take any chances. I got a second one, you may not!

            Robert
          • Leonard Meek
            Hi Bob. In ref to the high line voltage, I use an inrush current limiter in series with the power xfmr on all my radios and most test equip. This not only
            Message 5 of 10 , Sep 1, 2010
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              Hi Bob. In ref to the high line voltage, I use an inrush current limiter in
              series with the power xfmr on all my radios and most test equip. This not
              only lowers the applied line voltage slightly, but provides a softer start
              for the power xfrm and circuits. For the S-38 and its metal cabinet, there's
              a simple wiring change that'll ground the chassis and eliminate the shock
              hazzard. The change can be applied to other AC/DC sets as well, if you're
              not concerned with the originality.

              Leonard

              ----- Original Message -----
              From: "dr_telecom" <dr_telecom@...>
              To: <regenrx@yahoogroups.com>
              Sent: Wednesday, September 01, 2010 7:18 AM
              Subject: [regenrx] Re: Hot Chassis Wonder


              > Most of the kits in the 50s and early sixties had no power transformers.
              >
              > The Space Spanner, if I recall right, had a floating ground, but it was
              > connected with a resistor and parallel cap to the 'chassis' and you could
              > get a shock from it.
              >
              > Radios like the Hallicrafters S-38 series were a/c dc sets with hot
              > chassis. The case was not tied to the chassis - you had bushings that kept
              > them separate...but the bushings wear out over time, so beware. Just
              > don't touch the screw in the knob and ground at the same time.
              >
              > if you use these old radios, use an isolation transformer! Heathkit
              > made a nice one, and not only that, you can lower the line voltage a bit
              > ...the old radios were designed for 110v ac, and my line voltage here is
              > near 127v most of the time, or more than 10% high...stressing the parts in
              > the radio. If you have an old transformer operated radio....it will be
              > running with voltages on the high side, filament voltages on the high
              > side, and more heat in the case.
              >
              > Heahtkit was one of the few to put a power transformer in almost every
              > piece of gear they sold.
              >
              > THe Knight Span master (top of the line) had a power transformer. 6BZ6 and
              > 6AW8A tube and selenium rectifier. The Space Spanner did not - 12AT7,
              > 50C5, 35W4, and dropping resistor for filaments.
              >
              > Haven't gotten to the Ocean Hopper yet, but think it is 12AT6, 50C5 and
              > 35W4 type line up and dropping resistor, no power transformer.
              >
              > Many early sets (30s and 40s) had a line cord with built in dropping
              > resistor. They are real hazards now and most are bad.......
              >
              > All the A/C sets have live chassis, or ones separated by some caps...which
              > will give yo a shock if you touch the chassis , screw on a knob(if there
              > is one) etc......
              >
              > There weren't even polarized two pin plugs back then, and certainly no 3
              > wire cords with 3 pins.
              >
              > Some of the solid state stuff still has hot chassis.....cheap radios...use
              > a dropping capacitor off the line....no power xfrm.....but it is PC board,
              > and plastic push on knobs so you have to try to hard to get your fingers
              > where you can shocked.
              >
              > Bob, drT in Plano, TX
              >
              >
              >
              >
              >
              > ------------------------------------
              >
              > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo!
              > Groups Links
              >
              >
              >
              >
            • dr_telecom
              This is a good reason to use an isolation transformer! (or use space charge type circuits that only require 12v or 27v to operate...or go solid state with
              Message 6 of 10 , Sep 1, 2010
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                This is a good reason to use an isolation transformer! (or use space charge type circuits that only require 12v or 27v to operate...or go solid state with 9v.

                An isolation transformer helps with 'hot chassis' radios.

                I picked up a nice Heathkit one at a radio auction here.....has a small variac in it too to vary the line voltage a bit, too.

                Bob , drT in Plano TX


                --- In regenrx@yahoogroups.com, "Robert Bennett" <robertgjbennett@...> wrote:
                >
                > In a moment of absentmindedness and with the radio powered on, I
                > disconnected the earth by grabbing hold of the copper braid with both hands
                > and pulling the connection apart.
                >
                > I received 230 volts across my body from one hand to the other.
                >
                > It was an experience which I was very lucky to survive and for the past 50
                > years up to the present day, I am still frightened to work on line powered
                > equipment.
                >
                >
                > Robert
                >
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