Channel Vision CVT-2/8 PIAII cable amp

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  • bluto
    Badcaps Veteran
    • Oct 2007
    • 560
    #1

    Channel Vision CVT-2/8 PIAII cable amp

    My whole house video amp has conked out. It works for a while then quits. When it does the LED goes out. So I opened it up to see what I can see. There are three 'STONE' brand 'lytics (2x 100uf and 1x 10uf). They are a bad brand but read ok with a capacitance meter. I would just shotgun some new ones but It seems this board won't come out without un-soldering all of the connectors (I removed all the screws but it wasn't budging.


    So I looked at it some more and the 4 pin SMD transistor looking thing with the markings "DL 28" looked a little suspect. I thought maybe it was just a bad solder joint so I touched it up and the amp came back to life. So I left it plugged in on the bench but when I came back after a while the LED was out again. So in looking at it some more, it looks like it got hot and touching it confirms this suspicion. It has a steady 12v going into it but the output is fluctuating. When it is working, 9v is coming out and feeding down to the LED and the row of 5 more SMD transistors above the two 'lytics.

    So this seems like it could still be a easy fix if I could find a replacement for that flaky transistor. I have some chipquik so I think I could pull off replacing it.

    Any thoughts? How would I track down an equivalent part on digikey?
    Attached Files
    Tags: None
    • bluto
      Badcaps Veteran
      • Oct 2007
      • 560
      #2
      Re: Channel Vision CVT-2/8 PIAII cable amp

      Ok so if the failed part is just acting as a voltage regulator to take 12v down to 9v... Is there any reason why I couldn't just replace it with something like this:

      http://www.digikey.com/product-detai...711-ND/1828604

      A 12v to 9v regulator. I seems like it would fit in there without too much trouble.

        Comment

        • selldoor
          Slow Learner
          • Dec 2010
          • 7870
          #3
          Re: Channel Vision CVT-2/8 PIAII cable amp

          Are you sure it says DL 28 The tables I have looked at dont have a DL
          and the 28 could be ZB Can you try cleaning it up and checking.
          Please upload pictures using attachment function when ask for help on the repair
          http://www.badcaps.net/forum/showthread.php?t=39740

            Comment

            • bluto
              Badcaps Veteran
              • Oct 2007
              • 560
              #4
              Re: Channel Vision CVT-2/8 PIAII cable amp

              Its definitely "DL 28" It has "FF" inside the small circle in the middle. It is a SOT-89 package: 4.5mm x 2.5mm x 1.5mm. Looking at it with the tab on top it matches with the pin-out of another transistor data sheet where pin 1 was gate, pin 2 was drain, and pin 3 was source.

                Comment

                • bluto
                  Badcaps Veteran
                  • Oct 2007
                  • 560
                  #5
                  Re: Channel Vision CVT-2/8 PIAII cable amp

                  I went and looked at the one installed at my parents house. It is identical except a few years newer. It has Jackon caps instead of STONE. The device in question on that one is labeled "DL 5Y" if that helps any. I really want to fix this sucker. Any ideas on how to narrow down the search for this part?
                  Attached Files

                    Comment

                    • ReverendJones
                      Resurgam
                      • May 2010
                      • 49
                      #6
                      Re: Channel Vision CVT-2/8 PIAII cable amp

                      Hello Bluto.
                      The DL part code looks up as a 2SB798, a PNP transistor (The 28 & 5Y are date codes). The transistor driving it, L6, looks up as a 2SC1623A, a NPN transistor.
                      If the DL/2SB798 is heating up, there may also be a short somewhere on the output.

                      2SB798 datasheet
                      Machina improba! Vel mihi ede potum vel mihi redde nummos meos!

                        Comment

                        • bluto
                          Badcaps Veteran
                          • Oct 2007
                          • 560
                          #7
                          Re: Channel Vision CVT-2/8 PIAII cable amp

                          Thanks Reverend! It looks like it is an obsolete part but still available in a few places.

                            Comment

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