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1964 No Logo Deluxe Reverb Strange Issue

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  • 1964 No Logo Deluxe Reverb Strange Issue

    Strange issue after the amp is turned on, warmed up and the volume set to just about any level. If a string or a chord is struck or strummed the output level sounds a bit weak. If done again but this time the strings are struck or strummed harder the output level jumps up and stays there. Not talking about the volume going up because the strings are being hit harder, the actual output volume of the amp goes up. If the amp is shut down for a while and turned back on it does the same thing.

    If I remember correctly this amp has never been touched and is in great condition, everything inside is original and in good condition. I haven't been inside it in a while. It is here again but I haven't opened it up. The owner is not sure if he wants it gone through and recapped and anything else done other than the weird volume issue. Due to the condition of the amp, he does not use it to play out, just for practice.
    It's all about the bass. Lock in the groove and stay out of everyone else's way.

  • #2
    I would feed the amp a signal from a generator or ipod or phone, just not a guitar because you will need both hands. Turn the amp on and while it is cold probe around with a chopstick to see if moving, tapping, flexing or putting pressure on something makes it get louder suddenly. Include the speaker wires if they are not soldered. Check the speaker jack and plug connection. I had a Victoria 410 Bassman do this once, it turned out the speaker plug was faulty. Rock all tubes to see if there is a dodgy or oxidized socket. Check input jacks, does it do it on both, does it do it on both the Normal and the Reverb channels?
    It's weird, because it WAS working fine.....

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    • #3
      Yep, it sounds like a dirty, weak, corroded connection somewhere.
      If it ain't broke I'll fix it until it is...
      I have just enough knowledge to be dangerous...

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      • #4
        Thanks for the suggestion, I found it. I tapped around in the amp with no change until I tapped the volume pot connections. Re-soldered the connections, no change. Hooked it up to the scope and got a very bad looking sine wave. When I would play around with the volume control the sine wave would change. It would get cleaner and would occasional increase. There was a 47pf cap across the volume pot. tapping it made a slight difference but not every time. I pulled it out and it cleaned up the sine wave some. The amp does need to be recapped, they are all way over value. On to the next question. Not going to get a good looking sine wave until it's recapped.
        Last edited by J Luth; 07-11-2018, 10:01 PM.
        It's all about the bass. Lock in the groove and stay out of everyone else's way.

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        • #5
          I spoke to the owner and he has decided to go with recapping the amp. All of the 25/25 are way out, up to 140uf and bulging, most of the 16uf's are out a bit but are stating to bulge and leak. So they all have to go.

          He asked me a question that I am not sure of the correct answer.

          The main filter caps are 16uf 450v he asked if changing them to 22uf would change the sound of the amp? He was told by someone that they should be increased to 22uf. I told him I can do it either way he wants it.

          Any opinion's on that?
          It's all about the bass. Lock in the groove and stay out of everyone else's way.

          Comment


          • #6
            I haven't heard of caps being that far out of tolerance and higher UF. Are you certain of your testing methods? Try a known good/new cap with the same test. It's not uncommon for older caps to have higher than labeled values as tolerances were not as "good" in the day, but that seems extreme.

            On the filter caps, you won't notice any difference going from 16UF to 22UF and 22 is a standard value. If you do notice a difference, it's not because of the difference in value, it's more likely because the old caps are shot.
            Last edited by The Dude; 07-12-2018, 02:50 AM.
            "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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            • #7
              The old days saw caps with typical tolerance of +80/-20%. SO a typical 16uf cap can measure as high as 28uf and still be within spec. There is nothing with a critical value in a guitar amp.

              I recommend 22uf caps because they are a standard value, and available anywhere. 16uf is not a standard value. It might have been 50 years ago, but then I was just a college boy, and gas was cheap. So not only will it be easier and cheaper to go with 22uf, it won't even be outside the original specs. Modern caps are much closer tolerance.

              Will it change the sound of the amp? Probably, but not because of the value of those couple caps. it will change because it will now have new fresh caps. He likes the way the amp sounds with bloated, off-value, worn out caps. Nice fresh new caps are going to make the amp sound different. Will it make a Deluxe sound like a MArshall or something? No not at all. But it will sound more like a new Deluxe rather than an old tired one.
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Leaky caps can take longer to charge and fool some meters into thinking higher capacitance.
                Education is what you're left with after you have forgotten what you have learned.

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                • #9
                  If they are being measured in circuit, the parallel 1k5 cathode resistor may be misinterpreted by meter as a far higher capacitance.

                  Unsolder at least one leg for measuring.
                  Last edited by J M Fahey; 07-12-2018, 12:25 AM. Reason: brain fart
                  Juan Manuel Fahey

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                  • #10
                    Originally posted by J Luth View Post
                    I spoke to the owner and he has decided to go with recapping the amp. All of the 25/25 are way out, up to 140uf and bulging, most of the 16uf's are out a bit but are stating to bulge and leak. So they all have to go.

                    He asked me a question that I am not sure of the correct answer.

                    The main filter caps are 16uf 450v he asked if changing them to 22uf would change the sound of the amp? He was told by someone that they should be increased to 22uf. I told him I can do it either way he wants it.

                    Any opinion's on that?
                    I cannot help but mention that e-caps never go up in value by age, in fact capacitance reduces over time because the electrolyte dries out. Your measurement values seem to be the result of increased leakage conductance and a crude measuring principle/meter.

                    Increasing the filter caps to 22µ may slightly reduce the amp's responsiveness in favor of tighter lows.
                    Last edited by Helmholtz; 07-12-2018, 11:52 AM.
                    - Own Opinions Only -

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                    • #11
                      Increasing to 22µ will slightly reduce the amp's responsiveness in favor of tighter lows.
                      Assuming the original 16uf caps were actually 16uf to start with.
                      Education is what you're left with after you have forgotten what you have learned.

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                      • #12
                        Originally posted by J Luth View Post
                        So they all have to go.
                        Best plan yet. As for 22 uF "sounding different" as hi voltage filters, let's put it this way. Some people imagine they can hear a difference, and get all bent out of shape if the exact replacement part isn't installed. Those people, they're the reason the "Princess and the Pea" fable was written. Use 22's, and rest your mind, you've done the right thing.
                        This isn't the future I signed up for.

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                        • #13
                          If they are being measured in circuit, the parallel 1k5 cathode resistor may be misinterpreted by meter as a far higher impedance.
                          I guess you mean lower impedance.
                          - Own Opinions Only -

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                          • #14
                            Originally posted by Helmholtz View Post
                            I guess you mean lower impedance.
                            Sorry, brain fart, I meant higher *capacitance* , which is what we are talking about.
                            Thanks for the eagle eye.
                            Juan Manuel Fahey

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                            • #15
                              I gave you a thumbs up anyway. I knew what you meant.
                              "I took a photo of my ohm meter... It didn't help." Enzo 8/20/22

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