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no Can Capacitor on Leslie 122_Help needed

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  • no Can Capacitor on Leslie 122_Help needed

    I own a Hammond A-100 and a Leslie 122, I moved the organ recently
    and am checking the Leslie (a separate problem I might deal with
    in another post), while doing that I noticed that the Leslie Can capacitor was
    missing and as far as I can tell always was, so it looks like I’ve been using it as is for many years...

    So my question is and please pardon my ignorance on the subject, is that bad?…
    I'm not very knowledgable beyond basic maintenance, replacing basic parts and soldering 101
    so I'm very aware of my limitations ...

    just to be clear it’s the piece that should be on the COND spot on the 122 Tube Chart,
    it's referred to as a Leslie amp filter can capacitor also.

    I’ve used my A-100 &122 over the years for recordings
    without much issues but the usual maintenance & occasional service
    but I’m wondering how important it is to get one, I’ve seen places to get the part:

    https://www.tubesandmore.com/product...f-electrolytic

    is it something you can just install yourself much like a tube?

    any enlightenment about what it does also would be super.

    Thanks.

  • #2
    Most likely, some “clever” technician installed caps underneath the chassis instead of installing a can capacitor.

    In most cases where I have seem this done, the work was total crap quality, but occasionally it is nicely done.

    Remove your Leslie amplifier and post a photo of the underside, please.

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    • #3
      Thanks a lot,

      Will do, this will be my first time removing the Leslie amp, any things to watch out for ?

      Comment


      • #4
        I've done caps under the chassis on jobs where I wanted increased reliability on a amp that was going to be subject to the rigors of touring. It's all in how you do it. The can cap makers are simply not on the cutting edge of electrolytic capacitor manufacturing anymore. They may use Mallory's machinery, but they're not Mallory -- or Nichicon, Panasonic, or United Chemicon.
        I'm David. 'Dave' is someone else's name.

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        • #5
          Capacitors having 4 sections give 2 advantages
          - Only one ground point.
          - Fits exactly the existing hole.

          But also a very big inconvenience.
          -The price if you add the shippment outside US is dissuasive.

          For this reason, some technicians keep the can in place, disconnect and replace only the failed capacitor. This is the cheapest solution.

          If the 4 capacitors have been replaced by quality capacitors and if this has been done properly do not worry too much about that.

          JP

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          • #6
            Originally posted by Jyvoipabo View Post
            Capacitors having 4 sections give 2 advantages
            - Only one ground point.
            Actually, if you want to run the grounding of the power supply as effectively as possible, having only one ground point can be a disadvantage, not an advantage because all four sections unavoidably share the ground return path with the first stage power supply ripple. This is not a big deal in Leslie amps, but can be in higher-gain amps.
            I'm David. 'Dave' is someone else's name.

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            • #7
              Great info from everyone, especially for a novice like me.thanks a lot.

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              • #8
                Originally posted by David Anderson View Post
                Actually, if you want to run the grounding of the power supply as effectively as possible, having only one ground point can be a disadvantage, not an advantage because all four sections unavoidably share the ground return path with the first stage power supply ripple. This is not a big deal in Leslie amps, but can be in higher-gain amps.
                This especially applies in the AO28 preamp. We replaced the can caps with separates, and used a single ground point. Hum! We split the grounds as they were originally, and all was well.

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                • #9
                  How's that for irony. I just did exactly the same thing, to repair an AO-28 with discrete caps that had gone bad, and it's as quiet as can be.

                  Thinking back, that AO-28 only had 5 caps sharing a common ground....I think there was a couple of axial 25/25s or something mounted on the tag board. Maybe that's what made the difference.

                  Comment


                  • #10
                    One of the sections in the can behind the expression box is C26, the cathode bypass for the 12BH7 output stage. I suspect that it didn't like being grounded at the same spot as the first three supply stages.

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