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Speakeasy Vintage Preamp PA-122

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  • #16
    What is weird to me is that the brown wire , not the speed switch brown wire, has B+ voltage on it coming from the pedal! It is the one we hooked up to pin 5,after reading more I thought the B+ comes from the leslie not the pedal , so that can't be right as it does not change speeds. Right now that other brown wire ,the speed switch one, which I am calling the 7pin is not connected and out of the circuit. Maybe I hooked up the wrong brown wire?k

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    • #17
      Originally posted by kzinkmusic View Post
      What is weird to me is that the brown wire , not the speed switch brown wire, has B+ voltage on it coming from the pedal! It is the one we hooked up to pin 5,after reading more I thought the B+ comes from the leslie not the pedal , so that can't be right as it does not change speeds. Right now that other brown wire ,the speed switch one, which I am calling the 7pin is not connected and out of the circuit. Maybe I hooked up the wrong brown wire?k
      While it's not always life threatening or going to cause any damage, what you described was the scenario I wanted you to avoid. (coupling two B+ supplies together). There is no reason whatsoever for the B+ supply of the pedal to be sent to the Leslie.

      You should only attach Leslie pin 5 to the speed switch circuit and leave that other brown wire coming from pedal's own B+ alone. As far as I am concerned, it could probably be desoldered, and clipped out entirely (at least the section of it that runs to the 7 pin connector) to avoid causing future problems.

      Keep in mind that using pin 5 of the Leslie requires a healthy 10k 7 watt resistor inside the Leslie amp. On some Leslie amps, those resistors are tired, and can open up. They might seem to ohm out fine but open up when heated up or under load. So if you have problems after hooking up pin 5 properly, check every components' health including the 10k 7 watt in the 122 amp.

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      • #18
        Yes, I realized we had already done that , but know I understand the circuit better and know why it didn't work ,with your help. I will change out the brown wires and let you know.k

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        • #19
          I was out of town for a few weeks and when I got back we opened up the preamp pedal and measured voltages on both brown wires. When powered up and the switch is put in chorale the other brown wire does have the switching voltage. We changed the brown wires and the circuit works proper. We capped off the 7th pin brown wire as it is not necessary but still has that b+ voltage on it; still not sure why. Thanks for your help the preamp works great now and; if anyone needs help making a pigtail for one these units we could be of some assistance. k

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