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Re: [midatlanticretro] Commodore 64 SX

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  • evan@snarc.net
    ... Come check it out, you know what days I m there.
    Message 1 of 26 , Apr 3, 2009
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      >>> I welcome the chance to see a working model

      Come check it out, you know what days I'm there.
    • Jeffrey Brace
      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
      Message 2 of 26 , Apr 3, 2009
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        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.
         
        The guy whom I obtained this gem also mentioned that he could through other people get his hands on other vintage computers.  He has a garage full of all sorts of stuff (both vintage and not). He said he once threw out a brand new, never used, in the box TI/99 because it was getting in the way. On a whim he put this Commodore SX 64 on craigslist to see the response he would get. Some people have no idea what is in their hands.
         
        ----- Original Message -----
        Sent: Friday, April 03, 2009 10:31 PM
        Subject: RE: [midatlanticretro] Commodore 64 SX

        Weird, someone posts just seconds BEFORE my email asking if anyone's alive!

        I don't know the answer to your question but you are welcome to check out
        the cable for our SX64. The computer works fine so it's a good test bed.

        -----Original Message-----
        From: midatlanticretro@ yahoogroups. com
        [mailto:midatlanticretro@ yahoogroups. com] On Behalf Of arkaxow
        Sent: Friday, April 03, 2009 11:26 PM
        To: midatlanticretro@ yahoogroups. com
        Subject: [midatlanticretro] Commodore 64 SX

        I just picked up a Commodore 64 SX from someone through Craigslist. The
        problem is that it didn't come with a keyboard cable. Anyone know where I
        can locate one or how to make one ? It is a DB 25 to DB 25, Male to Male. I
        know I can use a printer cable and cut off the ends, but I want to see if I
        can do something a bit neater.

        Thanks :)

      • B Degnan
        ... I ll sell you a Plus/4 boxed and working if you want it. Name your price. Bill
        Message 3 of 26 , Apr 4, 2009
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          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
        • Bill Dromgoole
          I get all my cables from monoprice.com I ve always been satisfied with them. Try this six foot cable for $2.23
          Message 4 of 26 , Apr 4, 2009
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            I get all my cables from monoprice.com
            I've always been satisfied with them.

            Try this six foot cable for $2.23
            http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10212&cs_id=1021201&p_id=1583&seq=1&format=2

            Bill #3


            ----- Original Message -----
            From: "arkaxow" <ark72axow@...>
            To: <midatlanticretro@yahoogroups.com>
            Sent: Friday, April 03, 2009 11:26 PM
            Subject: [midatlanticretro] Commodore 64 SX


            I just picked up a Commodore 64 SX from someone through Craigslist. The problem
            is that it didn't come with a keyboard cable. Anyone know where I can locate
            one or how to make one ? It is a DB 25 to DB 25, Male to Male. I know I can use
            a printer cable and cut off the ends, but I want to see if I can do something a
            bit neater.

            Thanks :)
          • Joe Giliberti
            I thought I remember reading somewhere that the keyboard cable for the SX-64 differs from a standard DB-25. I think the connector is not as tall, as in the top
            Message 5 of 26 , Apr 4, 2009
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              I thought I remember reading somewhere that the keyboard cable for the SX-64 differs from a standard DB-25. I think the connector is not as tall, as in the top and bottom rows are closer together.

              On Sat, Apr 4, 2009 at 12:10 PM, Bill Dromgoole <drummy@...> wrote:

              I get all my cables from monoprice.com
              I've always been satisfied with them.

              Try this six foot cable for $2.23
              http://www.monoprice.com/products/product.asp?c_id=102&cp_id=10212&cs_id=1021201&p_id=1583&seq=1&format=2

              Bill #3



              ----- Original Message -----
              From: "arkaxow" <ark72axow@...>
              To: <midatlanticretro@yahoogroups.com>
              Sent: Friday, April 03, 2009 11:26 PM
              Subject: [midatlanticretro] Commodore 64 SX

              I just picked up a Commodore 64 SX from someone through Craigslist. The problem
              is that it didn't come with a keyboard cable. Anyone know where I can locate
              one or how to make one ? It is a DB 25 to DB 25, Male to Male. I know I can use
              a printer cable and cut off the ends, but I want to see if I can do something a
              bit neater.

              Thanks :)


            • christian_liendo
              I was going to buy that but the guy was not very nice.. I didn t know is was missing the cable
              Message 6 of 26 , Apr 4, 2009
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                I was going to buy that but the guy was not very nice.. I didn't know is was missing the cable

                --- In midatlanticretro@yahoogroups.com, "arkaxow" <ark72axow@...> wrote:
                >
                > I just picked up a Commodore 64 SX from someone through Craigslist. The problem is that it didn't come with a keyboard cable. Anyone know where I can locate one or how to make one ? It is a DB 25 to DB 25, Male to Male. I know I can use a printer cable and cut off the ends, but I want to see if I can do something a bit neater.
                >
                > Thanks :)
                >
              • jaj@totallyamused.com
                A DB25 male to DB25 male wired straight through does the trick. I believe you will need to shave down the ears on the plug the computer side to get a good fit.
                Message 7 of 26 , Apr 4, 2009
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                  A DB25 male to DB25 male wired straight through does the trick. I believe you will need to shave down the ears on the plug the computer side to get a good fit. There are some ribbon cable replacements (and some OEM) on ebay frequently, but you can likely build one for less than $10 buying all new parts.

                  Was this the one listed on NJ craiglist for the past 10 days or so? The (listed) price was pretty fair, I almost called about it - but I have too many irons in the fire already to pick up another piece of gear. Those SX64 keyboards can be finicky, there are several reference sites out there that describe how to clean them - time well spent.


                  Sent via BlackBerry by AT&T


                  From: "arkaxow"
                  Date: Sat, 04 Apr 2009 03:26:00 -0000
                  To: <midatlanticretro@yahoogroups.com>
                  Subject: [midatlanticretro] Commodore 64 SX

                  I just picked up a Commodore 64 SX from someone through Craigslist. The problem is that it didn't come with a keyboard cable. Anyone know where I can locate one or how to make one ? It is a DB 25 to DB 25, Male to Male. I know I can use a printer cable and cut off the ends, but I want to see if I can do something a bit neater.

                  Thanks :)

                • Jeffrey Brace
                  Joe, When I did my search I found this web site which explains it. Click on Keyboard Cable. :
                  Message 8 of 26 , Apr 4, 2009
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                    Joe,
                     
                    When I did my search I found this web site which explains it. Click on Keyboard Cable. :
                     
                    This web site hasn't been updated in years which is too bad, because the guy was trying to collect as many serial numbers as possible to get an accurate count on how many were actually made.
                     
                    Jeff
                     
                    ----- Original Message -----
                    Sent: Saturday, April 04, 2009 11:17 AM
                    Subject: Re: [midatlanticretro] Commodore 64 SX

                    I thought I remember reading somewhere that the keyboard cable for the SX-64 differs from a standard DB-25. I think the connector is not as tall, as in the top and bottom rows are closer together.

                    On Sat, Apr 4, 2009 at 12:10 PM, Bill Dromgoole <drummy@comcast. net> wrote:

                    I get all my cables from monoprice.com
                    I've always been satisfied with them.

                    Try this six foot cable for $2.23
                    http://www.monopric e.com/products/ product.asp? c_id=102&cp_id=10212&cs_id=1021201&p_id=1583&seq=1&format=2

                    Bill #3



                    ----- Original Message -----
                    From: "arkaxow" <ark72axow@msn. com>
                    To: <midatlanticretro@ yahoogroups. com>
                    Sent: Friday, April 03, 2009 11:26 PM
                    Subject: [midatlanticretro] Commodore 64 SX

                    I just picked up a Commodore 64 SX from someone through Craigslist. The problem
                    is that it didn't come with a keyboard cable. Anyone know where I can locate
                    one or how to make one ? It is a DB 25 to DB 25, Male to Male. I know I can use
                    a printer cable and cut off the ends, but I want to see if I can do something a
                    bit neater.

                    Thanks :)


                  • Brian Cirulnick
                    ... The ad *did* say it was missing the cable. From what I can see, you should be able to find a DB-25 male to male with all pins connected. They used to sell
                    Message 9 of 26 , Apr 6, 2009
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                      --- In midatlanticretro@yahoogroups.com, "christian_liendo" <christian_liendo@...> wrote:
                      >
                      > I was going to buy that but the guy was not very nice.. I didn't know is was missing the cable
                      >
                      ---------------

                      The ad *did* say it was missing the cable. From what I can see, you should be able to find a DB-25 male to male with all pins connected. They used to sell these as "serial cables" back in the modem days of the internet.

                      Then somebody got cheap and only wired up some of the pins (these are the ones with a thin-looking cable) -- just the seven (?) needed for the serial interface.

                      Belkin, I think, makes a good cable with all pins connected.

                      If you're desperate, let me know. I'm sure I have a small mountain of serial cables that are DB-25 with all pins connected. I can mail it or bring to "MARCH Spring Break 2009" (hosted by MTV)...
                    • 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 10 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 11 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 12 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 13 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 14 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 15 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 16 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 17 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 18 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 19 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 20 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 21 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 22 of 26 , Apr 11, 2009
                                              • 0 Attachment
                                                ----- 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 23 of 26 , Apr 12, 2009
                                                • 0 Attachment
                                                  --- 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 24 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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