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Capacitor testing

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  • Mike Loewen
    I tore apart my IMSAI in order to remove the four large electrolytic capacitors for testing/reforming. There are two 9500uf-30VDC caps and two 95000uf-15VDC
    Message 1 of 26 , Apr 6, 2009
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      I tore apart my IMSAI in order to remove the four large electrolytic
      capacitors for testing/reforming. There are two 9500uf-30VDC caps and two
      95000uf-15VDC caps. Here's the rig I put together for bringing them back
      to life:

      http://sturgeon.css.psu.edu/~mloewen/Oldtech/IMSAI/Reforming-L.jpg

      I put this together after reading many documents about testing old
      capacitors. Hidden behind the cap is an 8K power resistor in series with
      the cap. The small meter is measuring the voltage output from the the
      power supply (a HP 6443B 0-120VDC/2.5A unit), in this case 25.0 volts.
      The large meter is measuring the current flowing through the cap, 0.11ma.
      The voltage across the cap is 24.7V at this point.

      I started out by raising the voltage by steps, from 3-6-9-12-15-20-25,
      watching the current and making sure it went no higher than 0.5ma. At
      each step, I'd let the cap charge up until the current was down to about
      .05ma then increase the voltage. Once I got to 25.0 volts, I let it sit
      for a while until the current was down to .03ma.

      So far I've done one of the 9500uf caps. I'm hoping this procedure is
      effective. How about it, Dan and the rest of the electronics gurus?


      Mike Loewen mloewen@...
      Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
    • Ray Sills
      I always thought the Plus/4 was the unsung hero of the Commodore line. I had a couple at one time (donated to MARCH).. and always enjoyed the idea of the
      Message 2 of 26 , Apr 7, 2009
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        I always thought the Plus/4 was the unsung hero of the Commodore
        line. I had a couple at one time (donated to MARCH).. and always
        enjoyed the idea of the productivity software built into ROM. I
        liked the keyboard, too... and the compact size.

        73 de Ray

        On Apr 4, 2009, at 9:39 AM, B Degnan wrote:

        > Jeffrey Brace wrote:
        >>
        >> I welcome the chance to see a working model. Also I'm working on
        >> other "hard to find" commodore models. It's fun to find out that
        >> there are "other" commodore models out there that are not commonly
        >> known to many people.
        >>
        > I'll sell you a Plus/4 boxed and working if you want it. Name
        > your price.
        >
        > Bill
        >
        >
        >
      • B Degnan
        Do you have copies of any NTSC software for the Plus/4? Bill
        Message 3 of 26 , Apr 7, 2009
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          Do you have copies of any NTSC software for the Plus/4? 
          Bill

          Ray Sills wrote:
          I always thought the Plus/4 was the unsung hero of the Commodore  
          line.  I had a couple at one time (donated to MARCH).. and always  
          enjoyed the idea of the productivity software built into ROM.  I  
          liked the keyboard, too... and the compact size.
          
          73 de Ray
          
          On Apr 4, 2009, at 9:39 AM, B Degnan wrote:
          
            
          Jeffrey Brace wrote:
              
          I welcome the chance to see a working model.  Also I'm working on  
          other "hard to find" commodore models.  It's fun to find out that  
          there are "other" commodore models out there that are not commonly  
          known to many people.
          
                
          I'll sell  you a Plus/4 boxed and working if you want it.  Name  
          your price.
          
          Bill
          
          
          
              
          
          
          ------------------------------------
          
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        • B Degnan
          Mike, If I felt brave I might try to reproduce this. I have a similar power supply at work. Maybe I could set one of these up for the weekend of the 25th.
          Message 4 of 26 , Apr 7, 2009
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            Mike,
            If I felt brave I might try to reproduce this. I have a similar power
            supply at work. Maybe I could set one of these up for the weekend of
            the 25th. Anyone else coming?
            Bill

            Mike Loewen wrote:
            > I tore apart my IMSAI in order to remove the four large electrolytic
            > capacitors for testing/reforming. There are two 9500uf-30VDC caps and two
            > 95000uf-15VDC caps. Here's the rig I put together for bringing them back
            > to life:
            >
            > http://sturgeon.css.psu.edu/~mloewen/Oldtech/IMSAI/Reforming-L.jpg
            >
            > I put this together after reading many documents about testing old
            > capacitors. Hidden behind the cap is an 8K power resistor in series with
            > the cap. The small meter is measuring the voltage output from the the
            > power supply (a HP 6443B 0-120VDC/2.5A unit), in this case 25.0 volts.
            > The large meter is measuring the current flowing through the cap, 0.11ma.
            > The voltage across the cap is 24.7V at this point.
            >
            > I started out by raising the voltage by steps, from 3-6-9-12-15-20-25,
            > watching the current and making sure it went no higher than 0.5ma. At
            > each step, I'd let the cap charge up until the current was down to about
            > .05ma then increase the voltage. Once I got to 25.0 volts, I let it sit
            > for a while until the current was down to .03ma.
            >
            > So far I've done one of the 9500uf caps. I'm hoping this procedure is
            > effective. How about it, Dan and the rest of the electronics gurus?
            >
            >
            > Mike Loewen mloewen@...
            > Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/
            >
            >
            > ------------------------------------
            >
            > Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
          • Ray Sills
            HI Bill: No, I don t have any software for the Plus/4. Everything I had went to MARCH. It s possible there might be something in the basement storage area.
            Message 5 of 26 , Apr 7, 2009
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              HI Bill:

              No, I don't have any software for the Plus/4. Everything I had went
              to MARCH. It's possible there might be something in the basement
              storage area. Speaking of NTSC.. I used to use one of the Plus/4s at
              work, as a way to generate a title "slate" for recording music cues
              on to videotape. It worked quite well with the old Sony BVH-800 U-
              Matic 3/4" machines. But that was because the machines were not the
              least bit fussy about the quality of the video and the stability of
              the time base. Once we switched to professional Beta format, the
              Plus/4s didn't work properly. At that point, I got an Amiga (1000?)
              (Also now at MARCH) with a gen-lock board, and that worked like a
              champ. The gen-lock boards are at MARCH, too.

              73 de Ray

              On Apr 7, 2009, at 7:39 AM, B Degnan wrote:

              > Do you have copies of any NTSC software for the Plus/4?
              > Bill
              >
            • Brian Cirulnick
              ... Bill, put me down for a Plus/4... (if you ve got extras) Bring it to the MARCH fest, and I ll pay you then... ttyl Brian C.
              Message 6 of 26 , Apr 8, 2009
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                --- In midatlanticretro@yahoogroups.com, B Degnan <billdeg@...> wrote:
                >
                > I'll sell you a Plus/4 boxed and working if you want it. Name your price.
                >
                > Bill
                >---------------

                Bill, put me down for a Plus/4... (if you've got extras)
                Bring it to the MARCH fest, and I'll pay you then...

                ttyl
                Brian C.
              • Brian Cirulnick
                ... Speaking of NTSC.. I used to use one of the Plus/4s at ... If I recall, the VIC-20 was genlockable and was used quite extensively as a cheap Khyron. I
                Message 7 of 26 , Apr 8, 2009
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                  --- In midatlanticretro@yahoogroups.com, Ray Sills <raysills@...> wrote:
                  >
                  Speaking of NTSC.. I used to use one of the Plus/4s at
                  > work, as a way to generate a title "slate" for recording music cues
                  > on to videotape. It worked quite well with the old Sony BVH-800 U-
                  > Matic 3/4" machines. But that was because the machines were not the
                  > least bit fussy about the quality of the video and the stability of
                  > the time base. Once we switched to professional Beta format, the
                  > Plus/4s didn't work properly. At that point, I got an Amiga (1000?)
                  > (Also now at MARCH) with a gen-lock board, and that worked like a
                  > champ.
                  -------------------------

                  If I recall, the VIC-20 was "genlockable" and was used quite extensively as a cheap Khyron. I also used a C-64 setup for use as a teleprompter because it easily integrated with existing NTSC equipment in a video studio.

                  But yes, the Amiga was the champ when it came to the genlock. More Anime was fan-subtitled with the Amiga than probably any other system.

                  Mark Tilden (of Robosapien fame) originally built his own subtitling equipment for his anime releases. Sean Farquarson and I used his Amiga 500 and Mike Ling's genlock, while I typed up the scripts on my 1000.

                  Man, that was a lifetime ago....
                • Ray Sills
                  Hi Brian: Nah... the VIC-20 and C-64 video output was NTSC, but there was no direct way to genlock to house black. In fact, I used a VIC-20 and a C-64 for
                  Message 8 of 26 , Apr 8, 2009
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                    Hi Brian:

                    Nah... the VIC-20 and C-64 video output was NTSC, but there was no
                    direct way to genlock to house black. In fact, I used a VIC-20 and a
                    C-64 for making title slates before using the Plus/4. The VIC-20 was
                    actually handy due to the larger font.. easier to read at a distance
                    from the CRT. The Plus/4 was better in the sense that I was able to
                    create files that were easily appended to update projects.

                    I also wrote a little app in basic that would "run a stopwatch" as
                    the music was being recorded.. so although you didn't see TC per se..
                    you could see how far along you were in the recording.

                    73 de Ray

                    On Apr 8, 2009, at 12:20 PM, Brian Cirulnick wrote:

                    > --- In midatlanticretro@yahoogroups.com, Ray Sills <raysills@...>
                    > wrote:
                    >>
                    > Speaking of NTSC.. I used to use one of the Plus/4s at
                    >> work, as a way to generate a title "slate" for recording music cues
                    >> on to videotape. It worked quite well with the old Sony BVH-800 U-
                    >> Matic 3/4" machines. But that was because the machines were not the
                    >> least bit fussy about the quality of the video and the stability of
                    >> the time base. Once we switched to professional Beta format, the
                    >> Plus/4s didn't work properly. At that point, I got an Amiga (1000?)
                    >> (Also now at MARCH) with a gen-lock board, and that worked like a
                    >> champ.
                    > -------------------------
                    >
                    > If I recall, the VIC-20 was "genlockable" and was used quite
                    > extensively as a cheap Khyron. I also used a C-64 setup for use as
                    > a teleprompter because it easily integrated with existing NTSC
                    > equipment in a video studio.
                    >
                    > But yes, the Amiga was the champ when it came to the genlock. More
                    > Anime was fan-subtitled with the Amiga than probably any other system.
                    >
                    > Mark Tilden (of Robosapien fame) originally built his own
                    > subtitling equipment for his anime releases. Sean Farquarson and I
                    > used his Amiga 500 and Mike Ling's genlock, while I typed up the
                    > scripts on my 1000.
                    >
                    > Man, that was a lifetime ago....
                    >
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > Yahoo! Groups Links
                    >
                    >
                    >
                  • Christian Liendo
                    I remember a cable access show that used the VIC20.. I don t know how he did it without a genlock, but he had text on the bottom of the screen in the familiar
                    Message 9 of 26 , Apr 8, 2009
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                      I remember a cable access show that used the VIC20.. I don't know how he did it without a genlock, but he had text on the bottom of the screen in the familiar VIC-20 font... The show was "Rapid T Rabbit" and it was on Manhattan Public Cable Access.

                    • Ray Sills
                      If you put the video output of a VIC-20 (or any other device that could output NTSC) through a frame-sync .. that would make it work. A frame-sync is
                      Message 10 of 26 , Apr 8, 2009
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                        If you put the video output of a VIC-20 (or any other device that
                        could output NTSC) through a "frame-sync".. that would make it work.

                        A frame-sync is essentially a RAM buffer that will store a frame of
                        incoming video, and then play it back in sync with an external
                        reference.
                        TV stations do that all the time for incoming video feeds... since
                        there is no way to send timing signals to a remote source, so that it
                        would
                        be "in time" with local sources. All signals need to be in time in
                        order to matte a source to another video signal.. or to effect a
                        dissolve from one source to another. You can make a hard switch, but
                        then you run the risk of the whole system going out of time for a few
                        frames, and you would see the disruption on air.

                        One issue with using a frame-sync is that unless you -also- delay the
                        audio from the remote source, the video will be OK but the sound will
                        be ahead of the video, which is noticeable when you see a talking
                        head. (The old "lip-sync" issue). The situation can get worse when
                        stations use fancy digital switchers, since the video gets delayed on
                        -all- sources, not just the remote ones, If you see a TV show where
                        the audio is so far out of whack that it looks like a bad sci-fi
                        movie from another country, then you know there are uncompensated
                        audio paths.

                        73 de Ray



                        On Apr 8, 2009, at 1:15 PM, Christian Liendo wrote:

                        >
                        > I remember a cable access show that used the VIC20.. I don't know
                        > how he did it without a genlock, but he had text on the bottom of
                        > the screen in the familiar VIC-20 font... The show was "Rapid T
                        > Rabbit" and it was on Manhattan Public Cable Access.
                        >
                        >
                        >
                        >
                      • B Degnan
                        ... What do I look like, a store? just kidding I probably could be a store, sure I will sell you one, name your price (privately). Bill
                        Message 11 of 26 , Apr 8, 2009
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                          Brian Cirulnick wrote:
                          --- In midatlanticretro@yahoogroups.com, B Degnan <billdeg@...> wrote:
                            
                          I'll sell  you a Plus/4 boxed and working if you want it.  Name your price.
                          
                          Bill
                          ---------------
                              
                          Bill, put me down for a Plus/4... (if you've got extras)
                          Bring it to the MARCH fest, and I'll pay you then...
                          
                          ttyl
                          Brian C.
                          
                            
                          What do I look like, a store?  just kidding I probably could be a store, sure I will sell you one, name your price (privately).
                          Bill
                        • saturnine11
                          ... Hi Mike, I use a simpler, more effective method. Power supply negative to cap negative. Power supply positive to 30kohm resistor to cap positive.
                          Message 12 of 26 , Apr 11, 2009
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                            --- In midatlanticretro@yahoogroups.com, Mike Loewen <mloewen@...> wrote:
                            >
                            >
                            > I tore apart my IMSAI in order to remove the four large electrolytic
                            > capacitors for testing/reforming. There are two 9500uf-30VDC caps and two
                            > 95000uf-15VDC caps. Here's the rig I put together for bringing them back
                            > to life:
                            >
                            > http://sturgeon.css.psu.edu/~mloewen/Oldtech/IMSAI/Reforming-L.jpg
                            >
                            > I put this together after reading many documents about testing old
                            > capacitors. Hidden behind the cap is an 8K power resistor in series with
                            > the cap. The small meter is measuring the voltage output from the the
                            > power supply (a HP 6443B 0-120VDC/2.5A unit), in this case 25.0 volts.
                            > The large meter is measuring the current flowing through the cap, 0.11ma.
                            > The voltage across the cap is 24.7V at this point.
                            >
                            > I started out by raising the voltage by steps, from 3-6-9-12-15-20-25,
                            > watching the current and making sure it went no higher than 0.5ma. At
                            > each step, I'd let the cap charge up until the current was down to about
                            > .05ma then increase the voltage. Once I got to 25.0 volts, I let it sit
                            > for a while until the current was down to .03ma.
                            >
                            > So far I've done one of the 9500uf caps. I'm hoping this procedure is
                            > effective. How about it, Dan and the rest of the electronics gurus?
                            >
                            >
                            > Mike Loewen mloewen@...
                            > Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/

                            Hi Mike,

                            I use a simpler, more effective method. Power supply negative to cap negative. Power supply positive to 30kohm resistor to cap positive. Voltmeter across 30kohm resistor. Cap voltage determines the increments I raise the supply voltage in. For low voltage caps like yours, I just raise it smoothly until voltage hitting the cap is its rated voltage... but never exceeding 1ma to get there. If the cap can't be slowly raised to rated voltage without going over 1ma, the leakage current is too high and the cap is bad.

                            If the cap settles down to a low leakage at rated voltage (0.5ma or preferably much less), I'll next push the cap... by raising supply V until V hitting cap is 10% OVER the rated voltage... so 33volts and 16.5 volts for your examples. All the while keeping an eye on the leakage current as before.

                            Depending on how long since use, I'll let them sit at that voltage and low leakage rate for at least 30 mins... up to several hours... Then to finish, I slowly discharge the cap with a 1k resistor.

                            Since electrolytics are chemical devices, they can explode from overpressure caused from overheating from too high a *leakage current* (not the same as the charge current!) and otherwise be dangerous to work with if you don't know what you're doing. Always wear goggles.

                            JS
                          • Bill Dromgoole
                            ... From: saturnine11 To: Sent: Saturday, April 11, 2009 11:53 AM Subject: [midatlanticretro] Re:
                            Message 13 of 26 , Apr 11, 2009
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                              ----- Original Message -----
                              From: "saturnine11" <js@...>
                              To: <midatlanticretro@yahoogroups.com>
                              Sent: Saturday, April 11, 2009 11:53 AM
                              Subject: [midatlanticretro] Re: Capacitor testing


                              --- In midatlanticretro@yahoogroups.com, Mike Loewen <mloewen@...> wrote:
                              >
                              >
                              > I tore apart my IMSAI in order to remove the four large electrolytic
                              > capacitors for testing/reforming. There are two 9500uf-30VDC caps and two
                              > 95000uf-15VDC caps. Here's the rig I put together for bringing them back
                              > to life:
                              >
                              > http://sturgeon.css.psu.edu/~mloewen/Oldtech/IMSAI/Reforming-L.jpg
                              >
                              > I put this together after reading many documents about testing old
                              > capacitors. Hidden behind the cap is an 8K power resistor in series with
                              > the cap. The small meter is measuring the voltage output from the the
                              > power supply (a HP 6443B 0-120VDC/2.5A unit), in this case 25.0 volts.
                              > The large meter is measuring the current flowing through the cap, 0.11ma.
                              > The voltage across the cap is 24.7V at this point.
                              >
                              > I started out by raising the voltage by steps, from 3-6-9-12-15-20-25,
                              > watching the current and making sure it went no higher than 0.5ma. At
                              > each step, I'd let the cap charge up until the current was down to about
                              > .05ma then increase the voltage. Once I got to 25.0 volts, I let it sit
                              > for a while until the current was down to .03ma.
                              >
                              > So far I've done one of the 9500uf caps. I'm hoping this procedure is
                              > effective. How about it, Dan and the rest of the electronics gurus?
                              >
                              >
                              > Mike Loewen mloewen@...
                              > Old Technology http://sturgeon.css.psu.edu/~mloewen/Oldtech/

                              Hi Mike,

                              I use a simpler, more effective method. Power supply negative to cap
                              negative. Power supply positive to 30kohm resistor to cap positive. Voltmeter
                              across 30kohm resistor. Cap voltage determines the increments I raise the
                              supply voltage in. For low voltage caps like yours, I just raise it smoothly
                              until voltage hitting the cap is its rated voltage... but never exceeding 1ma to
                              get there. If the cap can't be slowly raised to rated voltage without going
                              over 1ma, the leakage current is too high and the cap is bad.

                              If the cap settles down to a low leakage at rated voltage (0.5ma or
                              preferably much less), I'll next push the cap... by raising supply V until V
                              hitting cap is 10% OVER the rated voltage... so 33volts and 16.5 volts for your
                              examples. All the while keeping an eye on the leakage current as before.

                              Depending on how long since use, I'll let them sit at that voltage and low
                              leakage rate for at least 30 mins... up to several hours... Then to finish, I
                              slowly discharge the cap with a 1k resistor.

                              Since electrolytics are chemical devices, they can explode from overpressure
                              caused from overheating from too high a *leakage current* (not the same as the
                              charge current!) and otherwise be dangerous to work with if you don't know what
                              you're doing. Always wear goggles.

                              JS



                              ------------------------------------

                              I don't see how your method is simpler or more effective than Mike's method.
                              I probably just don't understand your method.

                              If I understand you correctly you are putting a 30 Kohm resistor in series with
                              the Capacitor being rejuvenated and measureing the voltage across the resistor.
                              When the leakage current is equal to one milliampere the meter would read 30
                              volts and at 0.5 ma it would read 15 volts, etc.
                              The voltage accross the capacitor is unknown unless you have a seperate meter to
                              see the output voltage from the power supply.
                              You would then need to subtract the two voltages to get the capacitor voltage
                              unless you have a third meter to measure capacitor voltage.
                              The purpose of this exercise to to make a bad cap good again, if possible.

                              As you can see, I don't fully understand your method.
                            • saturnine11
                              ... the Capacitor being rejuvenated and measureing the voltage across the
                              Message 14 of 26 , Apr 12, 2009
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                                --- In midatlanticretro@yahoogroups.com, "Bill Dromgoole" <drummy@...> wrote:
                                > I don't see how your method is simpler or more effective than Mike's method.
                                > I probably just don't understand your method.
                                >
                                > If I understand you correctly you are putting a 30 Kohm resistor in series with
                                > the Capacitor being rejuvenated and measureing the voltage across the resistor.
                                > When the leakage current is equal to one milliampere the meter would read 30
                                > volts and at 0.5 ma it would read 15 volts, etc.
                                > The voltage accross the capacitor is unknown unless you have a seperate meter to
                                > see the output voltage from the power supply.
                                > You would then need to subtract the two voltages to get the capacitor voltage
                                > unless you have a third meter to measure capacitor voltage.
                                > The purpose of this exercise to to make a bad cap good again, if possible.
                                >
                                > As you can see, I don't fully understand your method.
                                >

                                << If I understand you correctly you are putting a 30 Kohm resistor in series with > the Capacitor being rejuvenated and measureing the voltage across the resistor.>>
                                ** That is correct. That configuration makes the approach simpler because of less equipment needed. You only need a variable PSU, voltmeter, and 3-5watt 30k resistor.

                                << When the leakage current is equal to one milliampere the meter would read 30 volts and at 0.5 ma it would read 15 volts, etc.>>
                                ** Correct.

                                << The voltage accross the capacitor is unknown unless you have a seperate meter to see the output voltage from the power supply.>>
                                ** Most variable PSU's have an output Volt/Ammeter built in. So you can either infer V across cap by subtracting the voltage drop across resistor from your PSU's voltage readout... OR you can just move one lead of your VDrop meter over to the cap's opposite terminal.. since you've already got one lead on it where the resistor is.


                                << unless you have a third meter to measure capacitor voltage. The purpose of this exercise to to make a bad cap good again, if possible.>>
                                ** Yeah, the purpose is to reform the oxide layer on the foil roll within the cap... assuming there's enough electolyte left in there to where it's not dried out, and assuming there's not shorts or other problems.

                                To recap, my method is simpler just in equipment setup, and also potentially gives you a longer cap life by the 10% push (the point of which is to give you more of an oxide layer.. well within the design limits of the caps).

                                jS
                              • Evan Koblentz
                                Hello new guy. Please introduce yourself, how you found us, etc.
                                Message 15 of 26 , Apr 12, 2009
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                                  Hello new guy. Please introduce yourself, how you found us, etc.
                                  > I use a simpler, more effective method .... JS
                                  >
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