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Giant Board circuit

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  • Glen Roger
    I need some help from some of you electrical engineer types!!! When I was resurrecting my ELF, I noticed that capacitors C1 and C4 (0.15uF) were broken.
    Message 1 of 7 , Sep 27, 2011
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      I need some help from some of you electrical engineer types!!!
      When I was resurrecting my ELF, I noticed that capacitors C1 and C4
      (0.15uF) were broken. Couldn't find 0.15 so I replaced them with
      0.10. The board seems to be working in most of its functions but I am
      struggling with RS-232. Is it possible that the wrong value for C4
      would cause this problem?
      Thanks.
      Glen
    • Raymond Siminas
      You can get .015uF very easily by connecting a 0.1uF and a 0.047uF in parallel.  Capacitance adds in parallel.  The thing to remember is that the formulas
      Message 2 of 7 , Sep 27, 2011
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        You can get .015uF very easily by connecting a 0.1uF and a 0.047uF in parallel.  Capacitance adds in parallel.  The thing to remember is that the formulas for capacitors in parallel are the same as resistors in series and that the formulas for capacitors in series are the same as resistors in parallel.  If you really want 0.15uF exactly, use 0.1uF, 0.047uF and three 0.001uF all in parallel wih each other, but it's probably not necessary unless it's being used in something that is very critical with timing


         




        --- On Tue, 9/27/11, Glen Roger <glenroger@...> wrote:


        From: Glen Roger <glenroger@...>
        Subject: [cosmacelf] Giant Board circuit
        To: cosmacelf@yahoogroups.com
        Date: Tuesday, September 27, 2011, 3:53 PM


         



        I need some help from some of you electrical engineer types!!!
        When I was resurrecting my ELF, I noticed that capacitors C1 and C4
        (0.15uF) were broken. Couldn't find 0.15 so I replaced them with
        0.10. The board seems to be working in most of its functions but I am
        struggling with RS-232. Is it possible that the wrong value for C4
        would cause this problem?
        Thanks.
        Glen







        [Non-text portions of this message have been removed]
      • Bee Dee
        Those pesky capacitors, doing everything backwards from resistors. They think they re all that and a bag of chips. Look at us! We re special! ;o) ... {snip}
        Message 3 of 7 , Sep 27, 2011
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          Those pesky capacitors, doing everything backwards from resistors.

          They think they're all that and a bag of chips.

          "Look at us! We're special!"

          ;o)


          --- In cosmacelf@yahoogroups.com, Raymond Siminas <lb_tiger39208@...> wrote:
          {snip}
          The thing to remember is that the formulas for capacitors in parallel are the same as resistors in series and that the formulas for capacitors in series are the same as resistors in parallel.
          {snip}
        • Glen Roger
          Thanks for the primer on capacitors. I m just wondering if someone who has the schematic and the electrical know-how can let me know if the capacitance at C1
          Message 4 of 7 , Sep 27, 2011
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            Thanks for the primer on capacitors. I'm just wondering if someone who has
            the schematic and the electrical know-how can let me know if the capacitance
            at C1 and C4 is responsible for the timing or voltage levels for the RS-232
            signal.

            Glen

            On Tue, Sep 27, 2011 at 10:17 PM, Bee Dee <bd@...> wrote:

            > **
            >
            >
            > Those pesky capacitors, doing everything backwards from resistors.
            >
            > They think they're all that and a bag of chips.
            >
            > "Look at us! We're special!"
            >
            > ;o)
            >
            >


            [Non-text portions of this message have been removed]
          • Aurel Boisvert
            Here is the wiring diagram of the Giant Board for your reference. ... -- Aurel [Non-text portions of this message have been removed]
            Message 5 of 7 , Sep 28, 2011
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              Here is the wiring diagram of the Giant Board for your reference.

              On 28/09/2011 2:31 AM, Glen Roger wrote:
              >
              > Thanks for the primer on capacitors. I'm just wondering if someone who has
              > the schematic and the electrical know-how can let me know if the
              > capacitance
              > at C1 and C4 is responsible for the timing or voltage levels for the
              > RS-232
              > signal.
              >
              > Glen
              >
              > On Tue, Sep 27, 2011 at 10:17 PM, Bee Dee <bd@...
              > <mailto:bd%40donnelly-house.net>> wrote:
              >
              > > **
              > >
              > >
              > > Those pesky capacitors, doing everything backwards from resistors.
              > >
              > > They think they're all that and a bag of chips.
              > >
              > > "Look at us! We're special!"
              > >
              > > ;o)
              > >
              > >
              >
              > [Non-text portions of this message have been removed]
              >
              >

              --
              Aurel



              [Non-text portions of this message have been removed]
            • ted_rossin
              Capacitors are usually no better than 10% of their stated value so 0.1uF and 0.047uF in parallel would be perfect . I ve never seen the giant board so I m
              Message 6 of 7 , Sep 28, 2011
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                Capacitors are usually no better than 10% of their stated value so 0.1uF and 0.047uF in parallel would be "perfect". I've never seen the giant board so I'm useless as to what these capacitors are used for.

                Could the caps be used for a charge pump to create -9V for RS-232? If so, too low of a value could mess that up. It seemed that folks didn't do charge pumps back then and instead required + and - 15V or 12V supplies.

                --- In cosmacelf@yahoogroups.com, Raymond Siminas <lb_tiger39208@...> wrote:
                >
                > You can get .015uF very easily by connecting a 0.1uF and a 0.047uF in parallel.  Capacitance adds in parallel.  The thing to remember is that the formulas for capacitors in parallel are the same as resistors in series and that the formulas for capacitors in series are the same as resistors in parallel.  If you really want 0.15uF exactly, use 0.1uF, 0.047uF and three 0.001uF all in parallel wih each other, but it's probably not necessary unless it's being used in something that is very critical with timing
                >
                >
                >  
                >
                >
                >
                >
                > --- On Tue, 9/27/11, Glen Roger <glenroger@...> wrote:
                >
                >
                > From: Glen Roger <glenroger@...>
                > Subject: [cosmacelf] Giant Board circuit
                > To: cosmacelf@yahoogroups.com
                > Date: Tuesday, September 27, 2011, 3:53 PM
                >
                >
                >  
                >
                >
                >
                > I need some help from some of you electrical engineer types!!!
                > When I was resurrecting my ELF, I noticed that capacitors C1 and C4
                > (0.15uF) were broken. Couldn't find 0.15 so I replaced them with
                > 0.10. The board seems to be working in most of its functions but I am
                > struggling with RS-232. Is it possible that the wrong value for C4
                > would cause this problem?
                > Thanks.
                > Glen
                >
                >
                >
                >
                >
                >
                >
                > [Non-text portions of this message have been removed]
                >
              • Richard
                C1 Is used as a pass cap. in the input circuit for the tape. C4 is connected as a filter for input of the rs232, this would remove high frequence noise. I
                Message 7 of 7 , Sep 29, 2011
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                  C1 Is used as a pass cap. in the input circuit for the tape.

                  C4 is connected as a filter for input of the rs232, this would remove high
                  frequence noise.
                  I don't think this is your problem.
                  Two Things I will mention.
                  Did you Remember To Contect An External negative 5 to 15v to the elf.
                  The other is the fact that alot of the software here is writen or modifyed
                  for flag 2, just check your copy.

                  one other note: When connected Right The Flag should held LOW With no Data
                  Flowing, you can check this at J12
                  on the giant board.

                  ----- Original Message -----
                  From: "Glen Roger" <glenroger@...>
                  To: <cosmacelf@yahoogroups.com>
                  Sent: Wednesday, September 28, 2011 2:31 AM
                  Subject: Re: [cosmacelf] Re: Giant Board circuit


                  > Thanks for the primer on capacitors. I'm just wondering if someone who
                  has
                  > the schematic and the electrical know-how can let me know if the
                  capacitance
                  > at C1 and C4 is responsible for the timing or voltage levels for the
                  RS-232
                  > signal.
                  >
                  > Glen
                  >
                  > On Tue, Sep 27, 2011 at 10:17 PM, Bee Dee <bd@...> wrote:
                  >
                  > > **
                  > >
                  > >
                  > > Those pesky capacitors, doing everything backwards from resistors.
                  > >
                  > > They think they're all that and a bag of chips.
                  > >
                  > > "Look at us! We're special!"
                  > >
                  > > ;o)
                  > >
                  > >
                  >
                  >
                  > [Non-text portions of this message have been removed]
                  >
                  >
                  >
                  > ------------------------------------
                  >
                  > ========================================================
                  > Visit the COSMAC ELF website at http://www.cosmacelf.comYahoo! Groups
                  Links
                  >
                  >
                  >
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