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  • Citation 12 failure...

    Hello,

    I have to admit it- I have made a partial mess out of my recapping of my old Citation 12 amp.

    Probably, the recapping is quite OK but I must have touched something on the board when adjusting the bias, so that when I connected the amp to the speakers, DC of probably quite a lot of amps, Went right into the woofer and destroyed it (Not a very big thing, a few hours work to replace it, but still....)

    Now the issue at hand: What shall I do with the amp? I have invested like 200 USD in new caps and one thing could be to replace all transistors. If so, the trouble would be to find adequate replacements (does anyone know that have done this?) Perhaps the transistors are getting oldish after 40+ years??

    Another would be to find and replace the one/few that is malfunctioning and that will be a challenge (advice on how to take the first steps in this would be greatly appreciated..)

    I NEVER give up! I will have that Cit12 operational att ANY cost in time or dineros!

    Best regards//lasse
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Re: Citation 12 failure...

    The bias pots may have been bad/dirty. I burned a channel on a 70's Pioneer Integrated when the bias made a big swing for a very small movement of the pot. In that case I know that nothing got shorted. Since then my practice has been to fully rotate the pot several times with no power, then return to the original position before starting adjustment.


    I can't find the links, but there are complete rebuild kits for Citation 12 available. Also check Nelson Pass' site for his mods to the Citation 12.
    I was so much older then, I'm younger than that now.
    OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
    Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
    Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
    Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
    LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

    Comment


    • #3
      Re: Citation 12 failure...

      I cloned that amp when I was a young kid and have made lots of comments on it
      over at DIY Audio. A modern replacement
      for the outputs would be the 2N3773, however what you really want is a single
      diffused type and I'm fairly certain that the 2N3773 is triple diffused. There is
      often smoke when the outputs go, so hope for the best.
      I believe that the outputs are socketed, pull them and test them as back to back
      diodes with an ohm meter - look it up if you don't know how.
      Let us know what you find.

      I always suggest putting in current limiting resistors in the rail paths when
      working on SS amps.

      Which rail is it stuck at? You might have just blown the small VAS transistor.
      A blown amp is like a crime scene, make as few changes as possible and save
      all the old parts.

      Comment


      • #4
        Re: Citation 12 failure...

        Originally posted by fastbike1 View Post
        The bias pots may have been bad/dirty. I burned a channel on a 70's Pioneer Integrated when the bias made a big swing for a very small movement of the pot. In that case I know that nothing got shorted. Since then my practice has been to fully rotate the pot several times with no power, then return to the original position before starting adjustment.


        I can't find the links, but there are complete rebuild kits for Citation 12 available. Also check Nelson Pass' site for his mods to the Citation 12.
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        Perry Mason talking to his dentist:

        "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

        Comment


        • #5
          Re: Citation 12 failure...

          Here's a couple of links.

          http://www.analogmetric.com/goods.php?id=993

          www.firstwatt.com/pdf/art_mos_citation.pdf

          Note I have no additional knowledge about the analogmetric kit. I think it claims to be based on Nelson Pass' mosfet design.
          I was so much older then, I'm younger than that now.
          OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
          Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
          Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
          Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
          LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

          Comment


          • #6
            Re: Citation 12 failure...

            Pick up a few Dummy load resistors with your next capacitor order.....sorry for your troubles.
            NLA

            Comment


            • #7
              Re: Citation 12 failure...

              safety first

              never use your speaker as a tester or a dummy load

              use current limiter either
              using lamp in series @ the ac voltage supply (simpler)
              or (100R) resistor in series at dc supply replacing the fuse

              always check your amp o/p for d/c voltage more than 100mV is unacceptable

              I think if you've time and ready to learn plus money to burn you can repair electronic stuff
              but probably not the newer swicthing and smd stuff

              Comment


              • #8
                Re: Citation 12 failure...

                Originally posted by lasse View Post
                [ATTACH=CONFIG]51760[/ATTACH][ATTACH=CONFIG]51761[/ATTACH][ATTACH=CONFIG]51762[/ATTACH]
                Do you have the schematic?
                You can pull out the driver boards and that might isolate the output transistors so
                that you can test them.
                Which rail does it go to when you power it up?

                Comment


                • #9
                  Re: Citation 12 failure...

                  I am PB2 here and there are many other Citation 12 threads there:
                  http://www.diyaudio.com/forums/solid...ansistors.html

                  That was some time ago, I would not use the 243/253 drivers since I found out that their
                  SOA is not very good. I'd probably go with BD139/140s instead.

                  Comment


                  • #10
                    Re: Citation 12 failure...

                    I know how you feel. The Pioneer was an SA-7800 in pristine condition.



                    I was so much older then, I'm younger than that now.
                    OS MTMs http://techtalk.parts-express.com/sh...d.php?t=220388
                    Swope TM http://techtalk.parts-express.com/sh...d.php?t=221818
                    Econowave and Audio Nirvana AN10 fullrange http://techtalk.parts-express.com/sh...d.php?t=216841
                    Imperial Russian Stouts http://techtalk.parts-express.com/sh...=1#post1840444
                    LECBOS. http://techtalk.parts-express.com/sh...ghlight=lecbos

                    Comment


                    • #11
                      Re: Citation 12 failure...

                      Originally posted by johnhenry View Post
                      safety first

                      never use your speaker as a tester or a dummy load

                      use current limiter either
                      using lamp in series @ the ac voltage supply (simpler)
                      or (100R) resistor in series at dc supply replacing the fuse

                      always check your amp o/p for d/c voltage more than 100mV is unacceptable

                      I think if you've time and ready to learn plus money to burn you can repair electronic stuff
                      but probably not the newer swicthing and smd stuff
                      Perry Mason talking to his dentist:

                      "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                      Comment

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