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Re: Vip Video

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  • DougCrawford
    My VIP had sync issues also with all my available monitors but one apparently very forgiving professional video monitor. I did the modification with the
    Message 1 of 20 , Jul 24, 2013
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      My VIP had sync issues also with all my available monitors but one apparently very forgiving professional video monitor.
      I did the modification with the transistor and it now syncs with an LCD monitor which previously did not work.

      I used an MPS222A from Radio Shack instead of a 2N2222 because it was available. On the output let I also substituted 47 ohm and 220 ohm as close enough.

      Here's photos of the result and the mod, done topside fairly cleanly.
      http://imgur.com/a/0VQ4i/all

      Amplitude of the sync pulse is about 1v.

      QUESTION: What resister value change would bring reduce the amplitude slightly?

      Thanks!
    • joshbensadon
      Hi Doug, That looks really good. Nice work! If you increase the resistor between Sync and the Transistor base, that should decrease the sync and increase
      Message 2 of 20 , Jul 24, 2013
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        Hi Doug,

        That looks really good. Nice work!

        If you increase the resistor between Sync and the Transistor base, that should decrease the "sync" and increase the "video". I'm partially guessing at the ciruit but it looks like a balance sort of thing. The 10K pull up gives the whole base circuit a general bias but the Spot (video) and /Sync outputs play off each other to make 3 voltage steps (White, Black, Sync). So changing either the Spot or Sync resistor will move that middle voltage (black), essentially changing the ratio of Video to Sync. To attenuate the whole signal, change the output resistors, 30/200, or what you used 47/220.

        Sometimes, it pays to just use trimmer pot(s).

        :)J


        --- In rcacosmac@yahoogroups.com, "DougCrawford" <touchetek@...> wrote:
        >
        > My VIP had sync issues also with all my available monitors but one apparently very forgiving professional video monitor.
        > I did the modification with the transistor and it now syncs with an LCD monitor which previously did not work.
        >
        > I used an MPS222A from Radio Shack instead of a 2N2222 because it was available. On the output let I also substituted 47 ohm and 220 ohm as close enough.
        >
        > Here's photos of the result and the mod, done topside fairly cleanly.
        > http://imgur.com/a/0VQ4i/all
        >
        > Amplitude of the sync pulse is about 1v.
        >
        > QUESTION: What resister value change would bring reduce the amplitude slightly?
        >
        > Thanks!
        >
      • DougCrawford
        Thanks very much for the analysis Josh! It was a good puzzle figuring out how to build this on top so that it was physically stable and free of shorting
        Message 3 of 20 , Jul 25, 2013
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          Thanks very much for the analysis Josh!
          It was a good puzzle figuring out how to build this
          on top so that it was physically stable and free of
          shorting possibilities. I was pretty happy with
          the result.

          Yes, when I looked at the result on the scope and thought
          about bringing the amplitude down a touch I thought
          wow a few trimmer pots would have been smart :)

          For those who might follow our steps here,
          the original circuit measured .5v sync without a load.
          That seemed to be in line with composite specifications.
          But when I connected the LCD monitor, the signal went to about nothing. So for me, I was looking for beefier drive not more amplitude. With the transistor, the sync pulse was 1v under load...
          looks like I got both, hence the thought of having some
          control over the amplitudes.

          I think I will leave it alone for now though. There is only
          a little bit of what looks like overdrive... some vertical line
          artifacts across the screen at regular intervals. Not
          enough to really bother me and it might be the monitor's problem.

          --- In rcacosmac@yahoogroups.com, "joshbensadon" <joshbensadon@...> wrote:
          >
          > Hi Doug,
          >
          > That looks really good. Nice work!
          >
          > If you increase the resistor between Sync and the Transistor base, that should decrease the "sync" and increase the "video". I'm partially guessing at the ciruit but it looks like a balance sort of thing. The 10K pull up gives the whole base circuit a general bias but the Spot (video) and /Sync outputs play off each other to make 3 voltage steps (White, Black, Sync). So changing either the Spot or Sync resistor will move that middle voltage (black), essentially changing the ratio of Video to Sync. To attenuate the whole signal, change the output resistors, 30/200, or what you used 47/220.
          >
          > Sometimes, it pays to just use trimmer pot(s).
          >
          > :)J
          >
          >
          > --- In rcacosmac@yahoogroups.com, "DougCrawford" <touchetek@> wrote:
          > >
          > > My VIP had sync issues also with all my available monitors but one apparently very forgiving professional video monitor.
          > > I did the modification with the transistor and it now syncs with an LCD monitor which previously did not work.
          > >
          > > I used an MPS222A from Radio Shack instead of a 2N2222 because it was available. On the output let I also substituted 47 ohm and 220 ohm as close enough.
          > >
          > > Here's photos of the result and the mod, done topside fairly cleanly.
          > > http://imgur.com/a/0VQ4i/all
          > >
          > > Amplitude of the sync pulse is about 1v.
          > >
          > > QUESTION: What resister value change would bring reduce the amplitude slightly?
          > >
          > > Thanks!
          > >
          >
        • joshbensadon
          ... Yes, it looks very good sitting on top of the PCB there. If you have some flux remover or 99% alcohol, you can clean just that area with a Q-Tip. ... I
          Message 4 of 20 , Jul 26, 2013
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            --- In rcacosmac@yahoogroups.com, "DougCrawford" <touchetek@...> wrote:
            >
            >
            > Thanks very much for the analysis Josh!
            > It was a good puzzle figuring out how to build this
            > on top so that it was physically stable and free of
            > shorting possibilities. I was pretty happy with
            > the result.


            Yes, it looks very good sitting on top of the PCB there.
            If you have some flux remover or 99% alcohol, you can clean just that area with a Q-Tip.


            > I think I will leave it alone for now though. There is only
            > a little bit of what looks like overdrive... some vertical line
            > artifacts across the screen at regular intervals. Not
            > enough to really bother me and it might be the monitor's problem.


            I agree, "Working" is good enough. Sometimes, I spend hours tracking down little glitches, and later regret wasting so much time when there are so many other fun projects that need attention.

            :)J
          • DougCrawford
            ... Yes as I looked back at the pics it occurred to me how nasty that flux looked. All done, thanks!
            Message 5 of 20 , Jul 27, 2013
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              >If you have some flux remover or 99% alcohol, you can clean just that area with a Q-Tip.

              Yes as I looked back at the pics it occurred to me how nasty that flux looked. All done, thanks!

              --- In rcacosmac@yahoogroups.com, "joshbensadon" <joshbensadon@...> wrote:
              >
              > --- In rcacosmac@yahoogroups.com, "DougCrawford" <touchetek@> wrote:
              > >
              > >
              > > Thanks very much for the analysis Josh!
              > > It was a good puzzle figuring out how to build this
              > > on top so that it was physically stable and free of
              > > shorting possibilities. I was pretty happy with
              > > the result.
              >
              >
              > Yes, it looks very good sitting on top of the PCB there.
              > If you have some flux remover or 99% alcohol, you can clean just that area with a Q-Tip.
              >
              >
              > > I think I will leave it alone for now though. There is only
              > > a little bit of what looks like overdrive... some vertical line
              > > artifacts across the screen at regular intervals. Not
              > > enough to really bother me and it might be the monitor's problem.
              >
              >
              > I agree, "Working" is good enough. Sometimes, I spend hours tracking down little glitches, and later regret wasting so much time when there are so many other fun projects that need attention.
              >
              > :)J
              >
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