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Re: C64/VIC 20 in video was Re: [midatlanticretro] Re: Plus/4

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  • 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 1 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 2 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 3 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 4 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 5 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 6 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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