Ad Widget

Collapse

Announcement

Collapse
No announcement yet.

Blues Deluxe Noise Issue

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
  • #1

    Blues Deluxe Noise Issue

    I have a Fender Blues Deluxe (original, not BDRI) with an unusual problem. When adjusting the volume there is a scratchy sound but it is not due to dirty pots (have cleaned and even replaced the Master pot). On the normal channel it is almost inaudible but I can hear it. It is very noticeable on the drive channel particularly with the Drive pot set for high gain. In this case any movement of the pot at any point in its range causes the noise. Since it seems to also happen on the normal volume (albeit to a lesser degree) I was thinking PI or power amp. For simple troubleshooting I swapped out all the tubes but there was no change. I don't know where to look next. Thoughts anyone?

    Fender-Blues-Deluxe-Schematic.pdf
    Tags: None
  • #2
    Are you speaking of R7? Check for DC on the pot.
    - Own Opinions Only -

    Comment

    • #3
      I was thinking PI or power amp.
      How would those stages know when you turned the control? I'm with Helmholtz, check for stray DC voltage on the noisy control. DC on a pot makes them noisy.

      You need to be aware there is only one channel through the amp. The "channels" you can switch between are really just gain changers switching in and out of the one channel.
      Education is what you're left with after you have forgotten what you have learned.

      Comment

      • #4
        Originally posted by Helmholtz View Post
        Are you speaking of R7? Check for DC on the pot.

        More R21 than R7.

        Are you alluding to the possibility of a leaky coupling cap at C9 ? (and C2 if I'm actually hearing the same thing on the normal volume, its hard to know for sure)

        Comment

        • #5
          Voltage is just a possibility. The thing to do is just measure for it. If we find it, we can figure out why it is there. If there is no voltage, then there is no voltage to explain. And we move on.
          Education is what you're left with after you have forgotten what you have learned.

          Comment

          • #6
            R21 would be the master pot. Whatever, check for DC across the scratchy pot(s). And yes, the usual suspects would be the plate coupling caps because the tube plates carry high DCV.
            Last edited by Helmholtz; 10-12-2019, 05:55 PM.
            - Own Opinions Only -

            Comment

            • #7
              Originally posted by Enzo View Post
              Voltage is just a possibility. The thing to do is just measure for it. If we find it, we can figure out why it is there. If there is no voltage, then there is no voltage to explain. And we move on.
              Cool, I'll check it out when I'll check it out when I get a chance.

              Comment

              • #8
                Originally posted by Helmholtz View Post
                R21 would be the common master pot.
                Not on this amp. They call it Master but it is only for the lead channel.

                Comment

                • #9
                  Originally posted by bobloblaws View Post
                  Not on this amp. They call it Master but it is only for the lead channel.
                  I see, the relay takes it out of circuit in clean mode. Forget "common".
                  - Own Opinions Only -

                  Comment

                  Previous template Next
                  Working...
                  X