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Leslie 860 speed issue

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  • Leslie 860 speed issue

    I have an 860 with a Combo Preamp III. It developed an issue where when you switch to the fast speed it starts to ramp up for a couple seconds, then goes to back to slow speed. The fast speed light stays lit up. Any Leslie guys out ther that might know what might be wrong?

  • #2
    Questions about Solid-State Leslie switching problems are coming up more frequently on the forum these days, probably due to the fact that 860s and similar models are >40 years old at this point.

    The problem with trying to answer your question is that the SS switching circuits are somewhat complicated (especially from the point of view of someone with little/no electronics experience) with a lot of components: transistors, relays, SCRs or Triacs, diodes, switches, multiple plug-socket contacts, etc...

    I could speculate at length about what might be wrong, but it would just be making a list. In the end, someone is going to have to get in there with diagnostic equipment and skills and figure out which link in the chain is failing. Your observation doesn't really narrow it down very much.
    I'm David. 'Dave' is someone else's name.

    Comment


    • Spiney1
      Spiney1 commented
      Editing a comment
      Yes, I understand it's complicated. I was hoping somebody could point me in the right direction, so that I could have my electronics tack look at it. I figured if somebody could give us some ideas it would decrease the amount of time he's going to have to spend diagnosing it. Thank you.

  • #3
    Hello,

    Yes, it is a little bit complicated :
    http://www.captain-foldback.com/Lesl...matics/860.gif (The speed control is in the left top corner of the schematics).
    But, diagram show an interisting 'control voltage chart' that explain correct voltage values in each configuration of the speed control (Halt,Slow,Fast)
    If you have a meter and some experience the first step is to check all the value and post a report.

    I don't beleive you have a problem with the relays or the pedal because the controls works. Not properly, but they works.

    JP

    Comment


    • Spiney1
      Spiney1 commented
      Editing a comment
      Thanks that's helpful. My tech seems to think it's the switch. But since it works for a while, I think it's something else. He's going to replace the fast switch in the Preamp, we'll see if that does any good. I'm thinking I need to find a tech that is familiar with Leslie's.

  • #4
    What happens if you switch the second footswitch button on the CPA III to Off instead of Slow and try to toggle between Fast and Off?

    I ask because the way the switching works in 11-pin Leslies, it shouldn't automatically default back to Slow. Two switches have to close for Slow speed to be engaged.
    I'm David. 'Dave' is someone else's name.

    Comment


    • Spiney1
      Spiney1 commented
      Editing a comment
      The stop switch functions normally.

  • #5
    Do you have a Multimeter? Have you checked for continuity between fast and ground pins when the preamp is set to fast? If I remember correctly from the 330 I had there are two grounds, one for switching and one for signal. This would at least eliminate either the pedal or the Leslie.

    You could also check continuity through the cable to eliminate that too.
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    Comment


    • Spiney1
      Spiney1 commented
      Editing a comment
      Thanks. My tech is replacing the speed switch. If that doesn't fix it, this gives us something else to look at.
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