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Re: [Electronics_101] TRANSISTOR VOLTAGE QUESTION

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  • Leon Heller
    ... From: berrysmountain To: Sent: Friday, June 03, 2005 4:11 AM Subject: [Electronics_101]
    Message 1 of 15 , Jun 2, 2005
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      ----- Original Message -----
      From: "berrysmountain" <berrysmountain@...>
      To: <Electronics_101@yahoogroups.com>
      Sent: Friday, June 03, 2005 4:11 AM
      Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION


      > Which NPN transistors currently available at retail electronics stores
      > can accept +6 volts on the collector, +1.2 volts on the emitter, and
      > +1.4 volts on the base?
      > How do I identify such a transistor before I purchase them?
      > What are the model numbers?
      > Will just about any general purpose transistor handle these voltages?

      Virtually any device will be OK, provided it will take the current you are
      designing for. I'd just use a 2N3904.

      You seem to have got the base and emitter voltages wrong for normal use -
      when the transistor is biased correctly there should be a 0.6 V difference
      between the base and emitter.

      Leon
      --
      Leon Heller, G1HSM
      http://www.geocities.com/leon_heller
    • berrysmountain
      The transistors I am attempting to replace are on an old electronic organ I am repairing. The voltages stated are as listed in the spec sheets for the organ. I
      Message 2 of 15 , Jun 3, 2005
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        The transistors I am attempting to replace are on an old electronic
        organ I am repairing. The voltages stated are as listed in the spec
        sheets for the organ. I am attempting to replace vintage transistors
        with new ones and I am looking for new replacements that would be
        equivalent to the old transistors.
        Any suggestions for replacing vintage with modern?


        --- In Electronics_101@yahoogroups.com, "Leon Heller"
        <leon.heller@d...> wrote:
        > ----- Original Message -----
        > From: "berrysmountain" <berrysmountain@y...>
        > To: <Electronics_101@yahoogroups.com>
        > Sent: Friday, June 03, 2005 4:11 AM
        > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
        >
        >
        > > Which NPN transistors currently available at retail electronics stores
        > > can accept +6 volts on the collector, +1.2 volts on the emitter, and
        > > +1.4 volts on the base?
        > > How do I identify such a transistor before I purchase them?
        > > What are the model numbers?
        > > Will just about any general purpose transistor handle these voltages?
        >
        > Virtually any device will be OK, provided it will take the current
        you are
        > designing for. I'd just use a 2N3904.
        >
        > You seem to have got the base and emitter voltages wrong for normal
        use -
        > when the transistor is biased correctly there should be a 0.6 V
        difference
        > between the base and emitter.
        >
        > Leon
        > --
        > Leon Heller, G1HSM
        > http://www.geocities.com/leon_heller
      • rtstofer
        Then the transistors may be germanium rather than silicon. This is going to be a problem. The physics of the devices are not at all the same. You can not
        Message 3 of 15 , Jun 3, 2005
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          Then the transistors may be germanium rather than silicon. This is
          going to be a problem. The physics of the devices are not at all
          the same. You can not substitute one for the other and have much
          success.

          You can find some sources of germanium transistors with Google. Is
          there no part number on the transistor?

          It would be something like 2Nxxx - probably a 3 digit number.

          --- In Electronics_101@yahoogroups.com, "berrysmountain"
          <berrysmountain@y...> wrote:
          > The transistors I am attempting to replace are on an old electronic
          > organ I am repairing. The voltages stated are as listed in the spec
          > sheets for the organ. I am attempting to replace vintage
          transistors
          > with new ones and I am looking for new replacements that would be
          > equivalent to the old transistors.
          > Any suggestions for replacing vintage with modern?
          >
          >
          > --- In Electronics_101@yahoogroups.com, "Leon Heller"
          > <leon.heller@d...> wrote:
          > > ----- Original Message -----
          > > From: "berrysmountain" <berrysmountain@y...>
          > > To: <Electronics_101@yahoogroups.com>
          > > Sent: Friday, June 03, 2005 4:11 AM
          > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
          > >
          > >
          > > > Which NPN transistors currently available at retail
          electronics stores
          > > > can accept +6 volts on the collector, +1.2 volts on the
          emitter, and
          > > > +1.4 volts on the base?
          > > > How do I identify such a transistor before I purchase them?
          > > > What are the model numbers?
          > > > Will just about any general purpose transistor handle these
          voltages?
          > >
          > > Virtually any device will be OK, provided it will take the
          current
          > you are
          > > designing for. I'd just use a 2N3904.
          > >
          > > You seem to have got the base and emitter voltages wrong for
          normal
          > use -
          > > when the transistor is biased correctly there should be a 0.6 V
          > difference
          > > between the base and emitter.
          > >
          > > Leon
          > > --
          > > Leon Heller, G1HSM
          > > http://www.geocities.com/leon_heller
        • berrysmountain
          Germanium it may be. The part number is SGS IW 9787. The two transistors I am trying to replace are on a small divider circuit board. I have removed this small
          Message 4 of 15 , Jun 3, 2005
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            Germanium it may be.
            The part number is SGS IW 9787.
            The two transistors I am trying to replace are on a small divider
            circuit board. I have removed this small board from the organ. I have
            the schematic for the divider circuit board. What if I build the
            circuit on a breadboard and solder that breadboard into the space
            left by the old divider board? Could new transistors be used?


            --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
            wrote:
            >
            > Then the transistors may be germanium rather than silicon. This is
            > going to be a problem. The physics of the devices are not at all
            > the same. You can not substitute one for the other and have much
            > success.
            >
            > You can find some sources of germanium transistors with Google. Is
            > there no part number on the transistor?
            >
            > It would be something like 2Nxxx - probably a 3 digit number.
            >
            > --- In Electronics_101@yahoogroups.com, "berrysmountain"
            > <berrysmountain@y...> wrote:
            > > The transistors I am attempting to replace are on an old
            electronic
            > > organ I am repairing. The voltages stated are as listed in the
            spec
            > > sheets for the organ. I am attempting to replace vintage
            > transistors
            > > with new ones and I am looking for new replacements that would be
            > > equivalent to the old transistors.
            > > Any suggestions for replacing vintage with modern?
            > >
            > >
            > > --- In Electronics_101@yahoogroups.com, "Leon Heller"
            > > <leon.heller@d...> wrote:
            > > > ----- Original Message -----
            > > > From: "berrysmountain" <berrysmountain@y...>
            > > > To: <Electronics_101@yahoogroups.com>
            > > > Sent: Friday, June 03, 2005 4:11 AM
            > > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
            > > >
            > > >
            > > > > Which NPN transistors currently available at retail
            > electronics stores
            > > > > can accept +6 volts on the collector, +1.2 volts on the
            > emitter, and
            > > > > +1.4 volts on the base?
            > > > > How do I identify such a transistor before I purchase them?
            > > > > What are the model numbers?
            > > > > Will just about any general purpose transistor handle these
            > voltages?
            > > >
            > > > Virtually any device will be OK, provided it will take the
            > current
            > > you are
            > > > designing for. I'd just use a 2N3904.
            > > >
            > > > You seem to have got the base and emitter voltages wrong for
            > normal
            > > use -
            > > > when the transistor is biased correctly there should be a 0.6 V
            > > difference
            > > > between the base and emitter.
            > > >
            > > > Leon
            > > > --
            > > > Leon Heller, G1HSM
            > > > http://www.geocities.com/leon_heller
          • Giuliani
            All the SGS IWxxxx I know, are silicon transistor. I think you can try with some 2N3904 or similar. The divider circuit should not be too critical. Bye.
            Message 5 of 15 , Jun 3, 2005
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              All the SGS IWxxxx I know, are silicon transistor. I think you can try
              with some 2N3904 or similar. The divider circuit should not be too critical.
               
              Bye.
              Giuliano 
              ----- Original Message -----
              Sent: Friday, June 03, 2005 4:30 PM
              Subject: [Electronics_101] Re: TRANSISTOR VOLTAGE QUESTION

              Germanium it may be.
              The part number is SGS IW 9787.
              The two transistors I am trying to replace are on a small divider
              circuit board. I have removed this small board from the organ. I have
              the schematic for the divider circuit board. What if I build the
              circuit on a breadboard and solder that breadboard into the space
              left by the old divider board? Could new transistors be used?
            • berrysmountain
              I agree, Giuliano. Thanks. ... try ... critical. ... have
              Message 6 of 15 , Jun 3, 2005
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                I agree, Giuliano.
                Thanks.


                --- In Electronics_101@yahoogroups.com, "Giuliani" <julcat@t...>
                wrote:
                > All the SGS IWxxxx I know, are silicon transistor. I think you can
                try
                > with some 2N3904 or similar. The divider circuit should not be too
                critical.
                >
                > Bye.
                > Giuliano
                > ----- Original Message -----
                > From: berrysmountain
                > To: Electronics_101@yahoogroups.com
                > Sent: Friday, June 03, 2005 4:30 PM
                > Subject: [Electronics_101] Re: TRANSISTOR VOLTAGE QUESTION
                >
                >
                > Germanium it may be.
                > The part number is SGS IW 9787.
                > The two transistors I am trying to replace are on a small divider
                > circuit board. I have removed this small board from the organ. I
                have
                > the schematic for the divider circuit board. What if I build the
                > circuit on a breadboard and solder that breadboard into the space
                > left by the old divider board? Could new transistors be used?
              • JanRwl@AOL.COM
                In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time, berrysmountain@yahoo.com writes: What if I build the circuit on a breadboard and solder that
                Message 7 of 15 , Jun 3, 2005
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                  In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time, berrysmountain@... writes:
                  What if I build the
                  circuit on a breadboard and solder that breadboard into the space
                  left by the old divider board? Could new transistors be used?
                  It's not whether the transistors are "new" or "old".  The older ones were quite probably made with germanium metal, and the "junction drop" in that is about 0.2 Volt.  Newer transistors are generally silicon, and the junction drop in that is about 0.6 volts.  This difference CAN make a difference in audio circuits, etc. 
                   
                  For irrelevant reasons, I'd NEVER work on an electronic "organ" unless it were a matter of [my!] life or death!  But if I were forced at gun-point, I'd ponder using a modern CMOS IC as a flip-flop.  WOULD require knowing some "working voltages" of many points, before beginning, of course.  GOOD LUCK!            Jan Rowland
                • Roy J. Tellason
                  ... I would think that pretty many would handle this, unless you re buying some of those really cheap bargain bag assortments or something. The only ones I
                  Message 8 of 15 , Jun 3, 2005
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                    On Thursday 02 June 2005 11:11 pm, berrysmountain wrote:
                    > Which NPN transistors currently available at retail electronics stores
                    > can accept +6 volts on the collector, +1.2 volts on the emitter, and
                    > +1.4 volts on the base?
                    > How do I identify such a transistor before I purchase them?
                    > What are the model numbers?
                    > Will just about any general purpose transistor handle these voltages?
                    > Thanks.

                    I would think that pretty many would handle this, unless you're buying some
                    of those really cheap bargain bag assortments or something. The only ones I
                    recall that tend to have really low breakdown voltages are ones designed to
                    handle really high frequencies too.

                    That's one consideration. You also need to figure on how much collector
                    current you need it to be able to pass, And how much power it needs to be
                    able to handle, which is not quite the same thing. And finally, how much
                    gain you need.
                  • Roy J. Tellason
                    ... What s the number on the original parts? The comments about needing 0.6V of voltage difference between base and emitter do NOT apply if the original part
                    Message 9 of 15 , Jun 3, 2005
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                      On Friday 03 June 2005 08:09 am, berrysmountain wrote:
                      > The transistors I am attempting to replace are on an old electronic
                      > organ I am repairing. The voltages stated are as listed in the spec
                      > sheets for the organ. I am attempting to replace vintage transistors
                      > with new ones and I am looking for new replacements that would be
                      > equivalent to the old transistors.
                      > Any suggestions for replacing vintage with modern?

                      What's the number on the original parts?

                      The comments about needing 0.6V of voltage difference between base and emitter
                      do NOT apply if the original part is germanium! In that case 0.2V is pretty
                      near normal...

                      You may even be able to find that original number out there. Let us know what
                      it is and I'll see what turns up.


                      > --- In Electronics_101@yahoogroups.com, "Leon Heller"
                      >
                      > <leon.heller@d...> wrote:
                      > > ----- Original Message -----
                      > > From: "berrysmountain" <berrysmountain@y...>
                      > > To: <Electronics_101@yahoogroups.com>
                      > > Sent: Friday, June 03, 2005 4:11 AM
                      > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
                      > >
                      > > > Which NPN transistors currently available at retail electronics stores
                      > > > can accept +6 volts on the collector, +1.2 volts on the emitter, and
                      > > > +1.4 volts on the base?
                      > > > How do I identify such a transistor before I purchase them?
                      > > > What are the model numbers?
                      > > > Will just about any general purpose transistor handle these voltages?
                      > >
                      > > Virtually any device will be OK, provided it will take the current
                      >
                      > you are
                      >
                      > > designing for. I'd just use a 2N3904.
                      > >
                      > > You seem to have got the base and emitter voltages wrong for normal
                      >
                      > use -
                      >
                      > > when the transistor is biased correctly there should be a 0.6 V
                      >
                      > difference
                      >
                      > > between the base and emitter.
                      > >
                      > > Leon
                      > > --
                      > > Leon Heller, G1HSM
                      > > http://www.geocities.com/leon_heller
                      >
                      > Yahoo! Groups Links
                      >
                      >
                      >
                    • Roy J. Tellason
                      ... Sure you can, in some circuits. :-) ... Or two letters followed by some digits, if it s a European number, or 2S followed by A or B and some digits,
                      Message 10 of 15 , Jun 3, 2005
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                        On Friday 03 June 2005 08:22 am, rtstofer wrote:
                        > Then the transistors may be germanium rather than silicon. This is
                        > going to be a problem. The physics of the devices are not at all
                        > the same. You can not substitute one for the other and have much
                        > success.

                        Sure you can, in some circuits. :-)

                        > You can find some sources of germanium transistors with Google. Is
                        > there no part number on the transistor?
                        >
                        > It would be something like 2Nxxx - probably a 3 digit number.

                        Or two letters followed by some digits, if it's a European number, or 2S
                        followed by A or B and some digits, if it uses the Japanese numbering
                        system, or... :-)

                        That's why I've become an "information packrat" these past couple of years.

                        > --- In Electronics_101@yahoogroups.com, "berrysmountain"
                        >
                        > <berrysmountain@y...> wrote:
                        > > The transistors I am attempting to replace are on an old electronic
                        > > organ I am repairing. The voltages stated are as listed in the spec
                        > > sheets for the organ. I am attempting to replace vintage
                        >
                        > transistors
                        >
                        > > with new ones and I am looking for new replacements that would be
                        > > equivalent to the old transistors.
                        > > Any suggestions for replacing vintage with modern?
                        > >
                        > >
                        > > --- In Electronics_101@yahoogroups.com, "Leon Heller"
                        > >
                        > > <leon.heller@d...> wrote:
                        > > > ----- Original Message -----
                        > > > From: "berrysmountain" <berrysmountain@y...>
                        > > > To: <Electronics_101@yahoogroups.com>
                        > > > Sent: Friday, June 03, 2005 4:11 AM
                        > > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
                        > > >
                        > > > > Which NPN transistors currently available at retail
                        >
                        > electronics stores
                        >
                        > > > > can accept +6 volts on the collector, +1.2 volts on the
                        >
                        > emitter, and
                        >
                        > > > > +1.4 volts on the base?
                        > > > > How do I identify such a transistor before I purchase them?
                        > > > > What are the model numbers?
                        > > > > Will just about any general purpose transistor handle these
                        >
                        > voltages?
                        >
                        > > > Virtually any device will be OK, provided it will take the
                        >
                        > current
                        >
                        > > you are
                        > >
                        > > > designing for. I'd just use a 2N3904.
                        > > >
                        > > > You seem to have got the base and emitter voltages wrong for
                        >
                        > normal
                        >
                        > > use -
                        > >
                        > > > when the transistor is biased correctly there should be a 0.6 V
                        > >
                        > > difference
                        > >
                        > > > between the base and emitter.
                        > > >
                        > > > Leon
                        > > > --
                        > > > Leon Heller, G1HSM
                        > > > http://www.geocities.com/leon_heller
                        >
                        > Yahoo! Groups Links
                        >
                        >
                        >
                      • Roy J. Tellason
                        ... Searching under that number didn t find me much, but changing that I to a 1 got me to this page: http://www.organservice.com/lowrey/991Parts.htm and
                        Message 11 of 15 , Jun 3, 2005
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                          On Friday 03 June 2005 10:30 am, berrysmountain wrote:
                          > Germanium it may be.
                          > The part number is SGS IW 9787.

                          Searching under that number didn't find me much, but changing that "I" to a
                          "1" got me to this page: http://www.organservice.com/lowrey/991Parts.htm

                          and searching within the page got me to this line:

                          991-011312-000 Transistor: 1W9787 NPN - Use 991-010462-000 0.80

                          and that one they're saying to use gets us to this line:

                          991-010462-000 Transistor: 2N2925, NPN 0.80

                          which is a _silicon_ transistor. You might get away with it in this
                          application, it's a pretty non-critical circuit.

                          I believe that "0.80" is probably their price, which seems pretty reasonable.

                          > The two transistors I am trying to replace are on a small divider
                          > circuit board. I have removed this small board from the organ. I have
                          > the schematic for the divider circuit board. What if I build the
                          > circuit on a breadboard and solder that breadboard into the space
                          > left by the old divider board? Could new transistors be used?

                          Yep, maybe...

                          It probably wouldn't hurt anything to try.

                          > --- In Electronics_101@yahoogroups.com, "rtstofer" <rstofer@p...>
                          >
                          > wrote:
                          > > Then the transistors may be germanium rather than silicon. This is
                          > > going to be a problem. The physics of the devices are not at all
                          > > the same. You can not substitute one for the other and have much
                          > > success.
                          > >
                          > > You can find some sources of germanium transistors with Google. Is
                          > > there no part number on the transistor?
                          > >
                          > > It would be something like 2Nxxx - probably a 3 digit number.
                          > >
                          > > --- In Electronics_101@yahoogroups.com, "berrysmountain"
                          > >
                          > > <berrysmountain@y...> wrote:
                          > > > The transistors I am attempting to replace are on an old
                          >
                          > electronic
                          >
                          > > > organ I am repairing. The voltages stated are as listed in the
                          >
                          > spec
                          >
                          > > > sheets for the organ. I am attempting to replace vintage
                          > >
                          > > transistors
                          > >
                          > > > with new ones and I am looking for new replacements that would be
                          > > > equivalent to the old transistors.
                          > > > Any suggestions for replacing vintage with modern?
                          > > >
                          > > >
                          > > > --- In Electronics_101@yahoogroups.com, "Leon Heller"
                          > > >
                          > > > <leon.heller@d...> wrote:
                          > > > > ----- Original Message -----
                          > > > > From: "berrysmountain" <berrysmountain@y...>
                          > > > > To: <Electronics_101@yahoogroups.com>
                          > > > > Sent: Friday, June 03, 2005 4:11 AM
                          > > > > Subject: [Electronics_101] TRANSISTOR VOLTAGE QUESTION
                          > > > >
                          > > > > > Which NPN transistors currently available at retail
                          > >
                          > > electronics stores
                          > >
                          > > > > > can accept +6 volts on the collector, +1.2 volts on the
                          > >
                          > > emitter, and
                          > >
                          > > > > > +1.4 volts on the base?
                          > > > > > How do I identify such a transistor before I purchase them?
                          > > > > > What are the model numbers?
                          > > > > > Will just about any general purpose transistor handle these
                          > >
                          > > voltages?
                          > >
                          > > > > Virtually any device will be OK, provided it will take the
                          > >
                          > > current
                          > >
                          > > > you are
                          > > >
                          > > > > designing for. I'd just use a 2N3904.
                          > > > >
                          > > > > You seem to have got the base and emitter voltages wrong for
                          > >
                          > > normal
                          > >
                          > > > use -
                          > > >
                          > > > > when the transistor is biased correctly there should be a 0.6 V
                          > > >
                          > > > difference
                          > > >
                          > > > > between the base and emitter.
                          > > > >
                          > > > > Leon
                          > > > > --
                          > > > > Leon Heller, G1HSM
                          > > > > http://www.geocities.com/leon_heller
                          >
                          > Yahoo! Groups Links
                          >
                          >
                          >
                        • Roy J. Tellason
                          ... Yeah, where the actual linear operation of the part is concerned. But this divider circuit he s talking about doesn t sound like that at all, and I
                          Message 12 of 15 , Jun 3, 2005
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                            On Friday 03 June 2005 03:34 pm, JanRwl@... wrote:
                            > In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time,
                            > berrysmountain@... writes:
                            >
                            > What if I build the
                            > circuit on a breadboard and solder that breadboard into the space
                            > left by the old divider board? Could new transistors be used?
                            >
                            > It's not whether the transistors are "new" or "old". The older ones were
                            > quite probably made with germanium metal, and the "junction drop" in that
                            > is about 0.2 Volt. Newer transistors are generally silicon, and the
                            > junction drop in that is about 0.6 volts. This difference CAN make a
                            > difference in audio circuits, etc.

                            Yeah, where the actual linear operation of the part is concerned. But this
                            divider circuit he's talking about doesn't sound like that at all, and I
                            don't think it's gonna be a problem there.

                            > For irrelevant reasons, I'd NEVER work on an electronic "organ" unless it
                            > were a matter of [my!] life or death! But if I were forced at gun-point,
                            > I'd ponder using a modern CMOS IC as a flip-flop.

                            Not me!

                            > WOULD require knowing some "working voltages" of many points, before
                            > beginning, of course. GOOD LUCK! Jan Rowland

                            I think this is the one he was talking about earlier on where only six volts
                            was present, though it isn't clear to me whether this is the actual measured
                            collector voltage or the power supply voltage.
                          • berrysmountain
                            Thanks, everyone for your thoughts and advice. The numbers printed on the transistors are: SGS 1W 9787 4640 (the 1 might be an I ). The transistor has a black
                            Message 13 of 15 , Jun 3, 2005
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                              Thanks, everyone for your thoughts and advice.
                              The numbers printed on the transistors are:
                              SGS 1W 9787 4640 (the 1 might be an "I").
                              The transistor has a black top and gray sides. The numbers are
                              printed in white on the gray sides. The transistor looks more like a
                              tiny smudge pot rather than like a shiney tin can. It doesn't look at
                              all like some of the newer ones with flat black sides.

                              Thanks for the search and the location of the
                              "2N2925, NPN 0.80" information on organservice.com





                              --- In Electronics_101@yahoogroups.com, "Roy J. Tellason"
                              <rtellason@b...> wrote:
                              > On Friday 03 June 2005 03:34 pm, JanRwl@A... wrote:
                              > > In a message dated 6/3/2005 9:33:21 A.M. Central Daylight Time,
                              > > berrysmountain@y... writes:
                              > >
                              > > What if I build the
                              > > circuit on a breadboard and solder that breadboard into the space
                              > > left by the old divider board? Could new transistors be used?
                              > >
                              > > It's not whether the transistors are "new" or "old". The older
                              ones were
                              > > quite probably made with germanium metal, and the "junction drop"
                              in that
                              > > is about 0.2 Volt. Newer transistors are generally silicon, and the
                              > > junction drop in that is about 0.6 volts. This difference CAN make a
                              > > difference in audio circuits, etc.
                              >
                              > Yeah, where the actual linear operation of the part is concerned.
                              But this
                              > divider circuit he's talking about doesn't sound like that at all,
                              and I
                              > don't think it's gonna be a problem there.
                              >
                              > > For irrelevant reasons, I'd NEVER work on an electronic "organ"
                              unless it
                              > > were a matter of [my!] life or death! But if I were forced at
                              gun-point,
                              > > I'd ponder using a modern CMOS IC as a flip-flop.
                              >
                              > Not me!
                              >
                              > > WOULD require knowing some "working voltages" of many points, before
                              > > beginning, of course. GOOD LUCK! Jan Rowland
                              >
                              > I think this is the one he was talking about earlier on where only
                              six volts
                              > was present, though it isn't clear to me whether this is the actual
                              measured
                              > collector voltage or the power supply voltage.
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