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  • Leslie 147 Fuse Blows

    Hi All

    I'm posting from South Africa. I have a Hammond C3 paired to a Leslie 147.

    Recently, the leslie stopped working, literally nothing happens when Hammond is powered up. I checked the fuse on the leslie, it was blown.
    I replaced it. It blows every time i switch on the power. The motors don't turn either on the rotating speakers. What I noticed is there is a very slight movement on the base rotating speaker before it stands still as the fuse blows.

    Any idea what it could be, what should I check or eliminate in sequence in trouble shooting?

    Your assistance is much appreciated. I'm a total amateur at this but being in South Africa means I have to try fix it myself!

    Franc

  • #2
    Originally posted by Phronck View Post
    Hi All

    I'm posting from South Africa. I have a Hammond C3 paired to a Leslie 147.

    Recently, the leslie stopped working, literally nothing happens when Hammond is powered up. I checked the fuse on the leslie, it was blown.
    I replaced it. It blows every time i switch on the power. The motors don't turn either on the rotating speakers. What I noticed is there is a very slight movement on the base rotating speaker before it stands still as the fuse blows.

    Any idea what it could be, what should I check or eliminate in sequence in trouble shooting?

    Your assistance is much appreciated. I'm a total amateur at this but being in South Africa means I have to try fix it myself!

    Franc
    usually if a fuse blows immediately, it’s a power transformer, rectifier diode, or filter cap. In some cases it could be a bad output tube but in that case the fuse lasts a bit longer befor blowing.

    Pull all the tubes, pull the filter cap out of its socket. This eliminates everything but the power trans and rectifier. Try it. If OK, plug the filter back in. If OK, plug the tubes back in starting with outputs. Assuming it passes the first test, whenever the problem returns it will be the part just put back in.

    Geo

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    • #3
      Thanks Geo, will give it a go.

      Comment


      • #4
        I pulled out tubes, filter cap - fuse still blows. Is it then either the transformer of rectifier?

        - - - Updated - - -

        Hi Geo

        I did as you said, pulled tubes and filter cap - fuse still blows. How can I test what if it's the transformer or rectifier?

        Thanks

        Franc

        Comment


        • #5
          Disconnect the two red wires going from the power transformer to the rectifier board. Be sure to tape up the ends of the disconnected red wires before applying power.

          With the red wires disconnected, if the fuse blows, it's probably the power transformer.

          Joe

          Comment


          • #6
            excuse my ignorance but which is the power transformer out of the square blocks on top of the amp? I also noticed there is a large round transformer inside the amp instead of a square one on top which i see on pics is normally the largest of three square units.

            Comment


            • #7

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              • #8
                The power transformer is the one closest to the rear of the amp chassis.

                Comment


                • #9
                  I disconnected the two red wires from the transformer to the rectifier - fuse is now fine and speaker motors turn.

                  It is therefore the rectifier?

                  Comment


                  • #10
                    Rectifier diodes are bad, at least one is shorted. I would replace all four diodes. 1N5408 diodes are good replacements (1000 volt/3 amp).
                    They are readily available on eBay. Here's just one listing:

                    https://www.--------/itm/10pcs-x-1n5...ss!08091!US!-1

                    Be sure to use the correct rating replacement fuse.

                    Joe

                    Comment


                    • #11
                      Thanks Joe - I see on B3Guys they sell 1000v 1amp 1N4007 diodes as replacements. Are these ok?

                      Comment


                      • #12
                        Yes, the 1N4007 is a 1000 volt/ 1 amp diode. These will work fine, but in my Leslie amps I used the heavier 1N5408 diodes, making the amp's rectifier section bulletproof.

                        Joe

                        Comment


                        • #13
                          Originally posted by joecool240 View Post
                          Yes, the 1N4007 is a 1000 volt/ 1 amp diode. These will work fine, but in my Leslie amps I used the heavier 1N5408 diodes, making the amp's rectifier section bulletproof.
                          If you read the datasheet on the 1N4007, you'll see that it's rated for momentary surges of up to 30 Amps. Steady-state B+ of a 147 is around 0.19 Amps. If you're drawing 1 Amp B+, you're in big trouble; if you're drawing >1A B+, your fuse should have blown a few miles back.

                          If a 3A diode makes you feel good, that's great, but it's only a psychological advantage, not a practical one. :-)
                          I'm David. 'Dave' is someone else's name.

                          Comment


                          • #14
                            David,

                            All very good and valid points, including your observation that the 3A diode "makes me feel good". :->:->:->

                            Joe

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                            • #15
                              Also consider that the ancestors of the 122 and 147, the first versions of the 22H and the 47, used a single 5U4GB, good for a maximum steady-state DC output current of ~0.275 Amps.
                              I'm David. 'Dave' is someone else's name.

                              Comment

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