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1990 Red Knob Twin - several problems including channel bleed or crossover

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  • 1990 Red Knob Twin - several problems including channel bleed or crossover


    My Red Knob twin started making a random frying bacon sound recently until the red led on channel one started blinking and eventually went out. The thing is that i replaced one of the stereo input jacks in channel 1 and accidentally lifted some of the pads. Now the overdrive channel is bleeding to the clean channel, meaning no clean channel anymore. The channel 1 red light never returned.

    I know its not a led problem in channel one as it does light up simultaneosly with the other led if you plug the guitar cable in channel 2. How to i tackle this problem?
    Attached Files

  • #2
    I see all sorts of connections in that 3rd picture needing solder. Is that after the jack replacement, or maybe when you were removing the old jack?
    "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

    Comment


    • #3
      It's hard to see what's going on at the jack with all that flux residue. Clean it up with some isopropyl alcohol and a swab or old toothbrush. Then take close up pictures of what is there.

      You mentioned both lights come on when you use ch.2 input (parallel ch. mode). What happens when you use ch.2 input and turn down gain and volume of ch.2? Does anything come through if you turn up ch.1 volume?
      Originally posted by Enzo
      I have a sign in my shop that says, "Never think up reasons not to check something."


      Comment


      • #4
        Some pictures where while changing the second clean channel stereo jack. Others after the swap.

        Both channel 1 and 2 led lights turn on when you plug the guitar in channel 2.

        Comment


        • #5
          Originally posted by Jquijano View Post
          Both channel 1 and 2 led lights turn on when you plug the guitar in channel 2.
          Yes, but what does the sound do when both lights are on? Does clean vol. work then? If you turn down gain and vol. of ch.2, is clean sound still distorted?

          Originally posted by Enzo
          I have a sign in my shop that says, "Never think up reasons not to check something."


          Comment


          • #6
            If you add gain or volume to channel 2 it also affects channel 1. Something is leaking.

            Comment


            • #7
              If you can't answer my questions, I can't help you. Sorry.
              Originally posted by Enzo
              I have a sign in my shop that says, "Never think up reasons not to check something."


              Comment


              • #8
                If i connect to channel 2 (parallel mode) jacks both leds light up, footswitch doesnt change anything. In that mode overdrive sounds differently more as Fuzz Type overdrive and the volume knob on channel 1 (clean channel) does affect the general volume of the amp if increased. It does the same if you select clean or overdrive with the footswitch.

                Comment


                • #9
                  So in parallel mode, if you turn ch.2 gain and volume all the way down, and just use clean volume, does the distortion bleed through, or is it clean?
                  Originally posted by Enzo
                  I have a sign in my shop that says, "Never think up reasons not to check something."


                  Comment


                  • #10
                    Problem was solved by an amp tech here in Panama. Apparently a diode and a 47k resistor were damaged. The only problem left is the reverb. Whenever you open the reverb over 2 it starts generating some crackling noise. How would you troubleshoot this?

                    Comment


                    • #11
                      Originally posted by g1 View Post
                      It's hard to see what's going on at the jack with all that flux residue. Clean it up with some isopropyl alcohol and a swab or old toothbrush. Then take close up pictures of what is there.

                      You mentioned both lights come on when you use ch.2 input (parallel ch. mode). What happens when you use ch.2 input and turn down gain and volume of ch.2? Does anything come through if you turn up ch.1 volume?
                      Got a quick question regarding the input jacks in this red knob twin. I tried getting the original replacement parts with the plastic back lid but it was really impossible. Nevetheless i have some Fender 9 pin stereo replacement jacks. What would be the safest method to remove and replace one of the jacks which is broken? USing solder wick and a chisel tip iron at 40watts? or would you use a solder sucker and the chisel tip iron?

                      Attached Files

                      Comment


                      • #12
                        Originally posted by Jquijano View Post

                        Got a quick question regarding the input jacks in this red knob twin. I tried getting the original replacement parts with the plastic back lid but it was really impossible. Nevetheless i have some Fender 9 pin stereo replacement jacks. What would be the safest method to remove and replace one of the jacks which is broken? USing solder wick and a chisel tip iron at 40watts? or would you use a solder sucker and the chisel tip iron?
                        Either but DON'T FORGET the FLUX!.
                        nosaj
                        soldering stuff that's broken, breaking stuff that works, Yeah!

                        Comment


                        • #13
                          Originally posted by Jquijano View Post
                          Problem was solved by an amp tech here in Panama. Apparently a diode and a 47k resistor were damaged. The only problem left is the reverb. Whenever you open the reverb over 2 it starts generating some crackling noise. How would you troubleshoot this?
                          Take it back to that tech! Or better to a different tech who know what she or he is doing.

                          Comment


                          • #14
                            Originally posted by nosaj View Post

                            Either but DON'T FORGET the FLUX!.
                            nosaj
                            Thanks ill apply some flux before the wick.

                            Comment


                            • #15
                              Originally posted by nosaj View Post

                              Either but DON'T FORGET the FLUX!.
                              nosaj
                              Input jack replacement done. I managed to remove the broken one with solder sucker.
                              Attached Files

                              Comment

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