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Leslie 770 - Fuse keeps blowing following lightning storm

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  • Leslie 770 - Fuse keeps blowing following lightning storm


    Was using my M3 with my Leslie 770 the other day when a lightning storm happend in our area.

    I've stopped playing but did not closed the organ.... it was still running.... when a lightning hit close to our housse. I've heard the power bar with an automatic breaker do its job for our television.... but my organ in not protected with that kind of bar.....

    When I went back to the organ an hour later, the leslie was no longer working..... the fuse is blown.

    I've replaced the fuse, powered on the organ and switch it to the Leslie and fuse blown again.....

    I've unpluged the Leslie from the organ. My M3 is working correctly in stand alone mode...... but I'm missing the Leslie....

    I believe there is something blown on the amp side but my knowledge limited on that side.....

    Do anybody know from where I should start my investigation ?


    P.S. Since that day, I've bought a protection power bar for my organ........


  • #2
    A voltage spike could damage a number of things in a Leslie 770. I just finished a rebuild of a 760. Off the top of my head, the first thing I'd look at would be the output transistors. They are connected pretty directly across the power supply rails and would get the full force of a voltage spike. If an output transistor is shorted, it would blow the fuse immediately when the speaker is turned on.

    Do not keep blowing fuses. This will only do more damage, especially since there is no DC protection of the speakers in these amps. Disconnect the speakers. You want to make sure the power amp channels are fixed and tested before reconnecting the speakers. You may also want to test the horn driver to make sure it didn't get damaged by DC across the voice coil.

    The M3 is vacuum tube based, and vacuum tubes are much more tolerant of voltage spikes than transistors.
    I'm David. 'Dave' is someone else's name.


    • #3
      If the fuse blows, it is because there is a short circuit somewhere.

      1- You must replace the fuse by (or insert in the line cord) a 40 / 60W filament lamp. This will avoid smoking tons of fuses. As long as you have not eliminated the short it will lit brightly.

      2-You must disconnect all connectors one by one (motors, amps) to try to locate the short.



      • #4
        Thanks Guys..

        David, for sure I did not continue to change the fuses. I fist changed it thinking it was blown by the lightening.

        Folowing your post, a friend of mine helped me and took a look at it. Like you've said, the output transistors were in problem. One of them was shorted, 2 were staying opened ans another one was heating. He got the replacement parts and will do the change this week.

        He has tested the horn driver and it wasn't affected by the problem.



        • #5
          Lightning these days are much different samples than before. The Earth is being subjected to magnetic energy from objects in space and the number of people and animals killed by lightning has increased all over the planet.

          If operating sensitive gear, even an air conditioner, best to keep track of weather conditions and turn off and UNPLUG your gear rather than risk a strike running through the grid and burning everything in its path.

          There are even incidences where a person got out of her car to escape lightning, went into a store that had the fire sprinkler system on top of the roof. The lightning hit the sprinkler system, the bolt traveled through all that, exited through the sprinkler nozzle in the ceiling, hit the woman standing under the nozzle, it went through her body and exited her foot burning a hole in the floor. She survived.

          There's been a lot of pink type plasma lightning occurrences where the lightning comes up from the ground, not from the atmosphere.

          I had my studio 3 ton air con blow up as a bolt hit the power grid transformer on the street behind the building. When it starts to rain and thunder I turn everything off.

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          If you've ever wondered why all the volcanic action lately it's because the magnetic energy from certain space objects heating up the iron core in the planet causing rocks to melt and bubble to the surface like a lava lamp.


          • #6

            If you have something electric that's totally disconnected from the grid, and lightning induces current in it, that current has nowhere to go. I've seen several times where there was identical machinery in a row and lightning stuck nearby; only the disconnected machines suffered damage.

            In my opinion, your best bet is to have everything plugged into good surge suppression and powered up. But it's a crapshoot because then you can get damage from brownouts unless you have everything on a UPS.

            For direct strikes, *all* bets are off. Power switches don't stop lightning current.

            The drastic solar minimums are causing increased lightning from cosmic rays. (We're at the peak of the second). Slowly but surely Birkeland gets the last laugh. Big Science is finally catching on.


            • #7
              True on the off chance lightning decides to use something or YOU as a rod. Sprinkler systems are a fave target of Zeus' rath.

              You'll see many instances where the timer or whatever is knocked across the neighbor's yard and it belongs to you, after the bolt traveled down a tree, through the dirt and hits payload of that pipe grid sitting under your Kentucky bluegrass.

              Solar minimum, at least in these modern times, is basically the same object(s) extruding energy from the sun.

              Most of the suns in our galaxy have binaries.

              But where's Waldo when you need to see him?

              Some binaries can't be seen without infra red.:-/

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              Beam me up, a "Scotty" gets this far infra red (sub-millimeter radiation) telescope named after him, the James Clerk Maxwell Telescope
              is being used to study event horizons. A previous version of this was the IRAS which, ahem, was decommissioned for conking out in space, so the report goes.

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              • #8
                "Normal" lightning actually starts from the ground, the charge moves rapidly up to the cloud layer, creating a type of plasma tunnel upwards, then returns via the same path - that's when you see the lightning bolt, that's why it appears to originate from the cloud. High speed slow-motion videography has captured this process.
                Other types of lighting are cloud to cloud, such as sheet lightning.
                Then there are "sprites" - lightning which originates high in the upper atmosphere and ejects upwards into space...... was only discovered since the advent of satellite photography, although it has been photographed from the ground in recent times.
                1971 T-202 with Carsten Meyer mods: Remove key click filters, single-trigger percussion, UM 16' drawbar volume correction. Lower Manual bass foldback.
                Korg CX3 (original 1980's analogue model).
                1967 Leslie 122 with custom inbuilt preamp on back panel for 1/4" line-level inputs, bass & treble controls. Horn diffusers intact.
                2009 Marshall 2061x HW Plexi head into Marshall 4x12 cabinet.

                1964 C3
                196x M-102
                197x X5
                197x Leslie 825


                • #9
                  Yeah it's like the plasma ball you see at the mall.

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                  • #10
                    More like this one
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                    • #11
                      Dass a beeg twinkie...:P