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A-105 vibrato quirk

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    A-105 vibrato quirk

    With volume on soft and vibrato on, it slightly works. Volume decreases with vibrato off. Volume increases with vibrato on, decreases on off. Vibrato sounds normal with increased expression pedal. HELP! I'm the second owner of this 1965 organ and vibrato scanner, to my knowledge, has not been cleaned or replaced. I don't understand why vibrato sounds normal with higher volume. Thanks for your input.

    #2
    It could be a tube issue, considering the overall volume differential between the vibrato and non vibrato channels. You could try switching V1 and V2, the two 6AU6 tubes and see if that changes anything. I’m sure much more knowledgeable people than me will have better solutions though.
    (2x) Hammond M3 Leslie 145
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      #3
      It's worth a try, thanks

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        #4
        To be honest, I found the description of the problem rather hard to follow.
        I'm David. 'Dave' is someone else's name.

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          #5
          When I get home, I'll recheck the issues and rewrite.

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            #6
            There is no vibrato with volume tab on soft, yes on normal. Volume decreases with vibrato off, increases when on. Volume on normal: vibrato works when on, volume decreases when off. Vibrato sounds normal when expression pedal is increased. I hope I've written these issues with more clarity. My thanks to all who can help.

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              #7
              The volume normal/soft tab is after the 12AX7 stages of the preamp and is common to both vibrato and non vibrato input channels.

              The preamp has 2 inputs A - non vib and B - vibrato. These are identical circuits with 6AU6 pentodes (V1 & V2). Try swapping V1 and V2. If the problem changes to the other channel, then you have a bad tube. The screen grid and plate resistors on these tubes are prone to failure (after 40 years) and are normally swapped out as part of a refresh.

              Jim

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                #8
                The reason I asked for clarification is that the Normal/Soft Volume tablets and the Chorus tablets are in the same box. On one occasion, I did run across an organ in which someone had worked on those switches and miswired them during reassembly by swapping two wires that are the same color. But that is a long shot. I forget the symptom it caused, but it was something strange.

                The Normal/Soft switch should only affect overall volume with some effect on tonal balance. It should not affect the amount of vibrato/chorus. If it does and it's not just a matter of perception based on loudness and/or tonal balance, something weird is going on.
                I'm David. 'Dave' is someone else's name.

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                  #9
                  There were no issues when I purchased the organ. It recently occurred. A friend had a 1958 B-3 with the same problem. He sold it as is so I don't know how it was fixed. Haven't exchanged tubes yet, when I do, I'll post the results. Thanks guys.

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