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  • Black Face Deluxe Reverb noise issue

    I have just completed a conversion of a reissue DR to a hand wired BFDR and have an issue that is driving me nuts. The amp's normal channel sounds fine always. The amps vibrato channel, however, sounds fine unless I plug in the reverb pan's "In" cord. Then I get a crackling noise in the output signal when driving the amp hard. This amp is an exact replica of a BFDR except for one thing; and that is I am using the original reissue style 1/4" TRS jack and foot pedal for switching the effects instead of the two RCA jacks and plugs like the original BFDR.

    I have replaced the reverb trannie, swaped tubes, rerouted wires put two original style RCA jacks on the back panel like the original BFDR in leau of the PCB jack assembly that came with the reissue, all to no avail. If I plug in the "Out" reverb pan cord by itself, everything is still fine. It is only when I plug in the "In" cord that I get the noise and it is there even if the "Out" cord is unplugged. I am now thinking about replacing the 1/4" TRS jack with two RCA jacks like the original to see if that helps.

    Has anyone ever experienced this before?

    Barry
    Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

  • #2
    Update: I have now replaced the 1/4" TRS jack with two RCA style jacks and the problem still remains. I'm at a loss as to how plugging in the reverb driver into the pan without the pan's output plugged into the reverb recovery could create this noise.
    Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

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    • #3
      Sounds like your hard driven signal is clipping the drive stage, and that might be coupling through the B+ or ground return or even radiating.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        I had a DR with exactly the same issue a couple of months ago. Changed tubes, changed pan, etc, nothing helped. Found out when scoping the reverb drive output that the driver stage had parasitic oscillations at high signal levels.
        I solved the problem by putting a small cap (I think it was 150pF) between pins 1/6 and 2/7 of the 12AT7.

        Of course it could also be clipping like Enzo said.

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        • #5
          Thanks for the comment Albert. I tried a 120pf cap (didn't have a 150pf) and it did reduce the noise some but it's still there. The other thing that is different from the original is I am using a back of pot ground buss for the entire preamp section (V1,2,3,4 and V5) of the amp. I think I will remove the circuit card grounds from the pot buss and individually ground them to the nearest chassis point. Maybe it is clipping and it is getting through the common preamp ground buss.
          Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

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          • #6
            Well I separated all of the board grounds, soldered ring terminals on the wires and them screwed them individually to the chassis right near each board connection. I still have the same problem.

            I'm racking my brain with this. It just doesn't make sense that if I unplug the "In" cord the noise goes away and with it connected it's there. What does having the "In"cord and pan input hanging on the reverb trannie jack which is connected to the B+ and driver tube (without a return signal from the pan) change in the circuit to turn the noise on and off? If the Reverb driver tube is clipping and being picked up through a shared ground or B+ why doesn't it keep doing so without the "In" cord and pan "In" connected to the jack?
            Last edited by bnwitt; 09-18-2010, 08:27 PM.
            Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

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            • #7
              Just for kicks try removing one of the reverb tranny bolts and pivot the reverb tranny 90* either way.

              I do think it's a parasitic that only happens when current is present in the reverb circuit. But try this anyway.

              Chuck
              Last edited by Chuck H; 09-18-2010, 09:27 PM.
              "Take two placebos, works twice as well." Enzo

              "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

              "If you're not interested in opinions and the experience of others, why even start a thread?
              You can't just expect consent." Helmholtz

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              • #8
                have you changed the cables? I did the same build with a drri and the cables were pretty crappy. I've definitely found reverb tank cable RCAs to be some of the hardest working RCAs (my winner is the 12-15' car leads, buried under a carpet and rejecting ignition coils) out there- think of all that radiated EM noise, vibration and, at the chassis end, heat! Reverb cables- placement and quality- have definitely been issues with builds and work i've done. Easy thing to try too.

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                • #9
                  Thanks for the replies Chuck and NorCal. Yes I've swapped cables, reverb pans, reverb trannie, driver tube, just about everything there is to swap. I'm going to try some different value caps across the driver tube plates and grids like Albert suggested. The 120pf didn't work but that doesn't mean a higher or lower value won't. I'll try the reverb trannie spin thing too.
                  Warning! Some Electronics devices contain lethal voltages that can kill you. If you do not feel qualified to work with dangerous voltages, refer your repairs to a qualified technician. By giving you online advice, I am assuming no liability for any injury or damages you might incur through your own actions.

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                  • #10
                    SO have we scoped the drive circuit? The difference with the pan plugged in is that the circuit is loaded. Just why that matters we do not yet know, but that it makes the difference doesn't mystify me.
                    Education is what you're left with after you have forgotten what you have learned.

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                    • #11
                      I had a similar problem with the same build(rebuild ?). Turned out it was a faulty ground in the footswitch. Are you using the Fender supplied unit that came with your DRRI? I opened mine up and found the some very poor soldering. That fixed mine.

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