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6550 Tube Choices?????

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  • 6550 Tube Choices?????

    <BLOCKQUOTE>


    Well... after much cleaning and exploring... I've had my way with this old amp.... I noticed the capacitors underneath had the date 11-79 on them and yet they look brand new *I was born in 1979... lol* I've been kind of researching this broken tube.. the 6550.. seems it was invented by Tung-Sol in 55' was originally pear-shaped like the OC3 regulator tube on mine... etc.... is there a good brand I should use that suits the Leslie more than others? Should I buy a pair or a whole set? They're rather expensive... :|</P>


    </P></BLOCKQUOTE>

  • #2
    Re: 6550 Tube Choices?????

    <TABLE class="" width=560 border=0>
    <TBODY>
    <TR>
    <TD class="" width=284 height=20><SPAN class=style13><FONT face=Verdana>6550 Power Tubes - Matched Pair
    (Always replace in pairs) </FONT></SPAN></TD>
    <TD class="" align=middle width=82 height=20><SPAN class=style13><FONT face=Verdana>$75.00
    (pair) </FONT></SPAN></TD>
    <TD class="" align=middle width=103 height=20><SPAN class=style13><FONT face=Verdana>$70.00 (pair)</FONT></SPAN></TD></TR></TBODY></TABLE>
    <P mce_keep="true"></P>


    Erm.... Yeah......</P>

    Comment


    • #3
      Re: 6550 Tube Choices?????



      You can do a little better than $70, maybe $55 from commercial sources.  Look at http://www.tubesandmore.com. From http://www.esrcvacuumtubes.com/ you can buy single Tung-Sol 6550's for $3.00.</p>

      You may find that matched pairs vs. non-matched won't make an audible difference in this application.   For $3.00 each, you won't lose much by trying :)  Or buy 10 of them, and locate someone with a good mutual conductance tube tester and match them yourself ... (Contact the local Tulsa ham radio club -- http://w5ias.com/ -- somebody there will have an appropriate tester).</p>

        </p>

        </p>

      Comment


      • #4
        Re: 6550 Tube Choices?????

        <BLOCKQUOTE>


        Grant... being the highly motivated lazy SOB I am.... I saw the $3.00 and my heart began to beat faster... lol... I'll look into those sources for sure as a start... good thing I haven't bought that pre-paid Wal-Mart Visa card yet */action chooses not to carry plastic* And I saw a tube tester on ebay going for $10.00.... guess I'll have to study up on "mutual conductance".... it's like one of those 101 project kits from Radio Shack when I was kid.... hahaha..... I'll just have to set the amp aside and work on the motors for now... patience is a virtue... or is it? :))))</P></BLOCKQUOTE>

        Comment


        • #5
          Re: 6550 Tube Choices?????



          If I can help you in any way, I just worked on a 122 Leslie at a church where these tubes went bad. </p>

          They are a matched set and you should always replace them in pairs. You also have to pay attention that you do not mix the new ones up with the old ones. You can do some serious damage to your amp. </p>

          A decent indicator that your tubes have a problem is in the way they glow. If one looks like they are on fire. You may have a weak one. </p>

          If the sound is distorted when the amp is turned up, they may be going. </p>

          My best advise is: I f you do not understand the situation, send the amp to a specialist. The B3Guys and/or the others know their craft so do not take a chance of ruining the amp.</p>

          Good Luck!
          </p>

          Comment


          • #6
            Re: 6550 Tube Choices?????

            [quote user="theorganloft"]


            </p>

            They are a matched set and you should always replace them in pairs.  You also have to pay attention that you do not mix the new ones up with the old ones.  You can do some serious damage to your amp.  
            </p>

            [/quote]</p>

            The worst thing that will happen to you is that you will possibly increase cross-over distortion in a Class B amp.  Even that can be mitigated if the amp has bias adjustments for the tubes. If the plate of either tube is running so hot that it is turning red, you could have a severe bias problem in the amp, or an internal tube short -- neither of which would be good news and could severely stress the power transformer if it doesn't have protective circuitry.    But generally good tubes would have to be really grossly mismatched (one of them actually bad) to damage the amplifier.</p>

            Of course, if one pulls two old tubes from unknown manufacturers from somebody's junk box -- well, you take your chances :)</p>

            Comment


            • #7
              Re: 6550 Tube Choices?????

              [quote user="Grant_Youngman"][quote user="theorganloft"]


              </p>

              They are a matched set and you should always replace them in pairs. You also have to pay attention that you do not mix the new ones up with the old ones. You can do some serious damage to your amp.
              </p>

              [/quote]</p>

              The worst thing that will happen to you is that you will possibly increase cross-over distortion in a Class B amp. Even that can be mitigated if the amp has bias adjustments for the tubes.If the plate of either tube is running so hot that it is turning red, you could have a severe bias problem in the amp, or an internal tube short -- neither of which would be good news and could severely stress the power transformer if it doesn't have protective circuitry. But generally good tubes would have to be really grossly mismatched (one of them actually bad) to damage the amplifier.</p>

              Of course, if one pulls two old tubes from unknown manufacturers from somebody's junk box -- well, you take your chances :)</p>

              [/quote]</p>

              </p>

              You are correct about the Bias but I was more concerned about his safety. A tube amp can be lethal to the uninformed. As you know, only experienced technicians should go in there. We can give advise but I do not want to use a forum like this to get a fellow killed.
              </p>

              Comment

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