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super reverb output values, please

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  • #16
    yes

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    • #17
      Rearranging the power formula we get E=Squareroot(P*R)

      So 50W at 2 ohms = 10V(RMS). That's 28V peak to peak. How much are you getting. Do you have a 2 ohm dummy load? What do you use as a speaker load? Does the output transformer have any other taps?
      WARNING! Musical Instrument amplifiers contain lethal voltages and can retain them even when unplugged. Refer service to qualified personnel.
      REMEMBER: Everybody knows that smokin' ain't allowed in school !

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      • #18
        >Do you have a 2 ohm dummy load? What do you use as a speaker load?
        No. An 8 ohm 250 watt non inductive load.
        >Does the output transformer have any other taps?
        No, it is the original transformer, just two leads

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        • #19
          Originally posted by Tom Phillips View Post
          No offense but your last statement is actually humorous in that it indicates a case of incorrect mindset troubleshooting.
          There are many faults that could cause low power output. Don't just assume that the most expensive part in the amp is bad. Step back for a while, think about it and then continue with your troubleshooting.

          I hope you find something simple like an open ten cent plate resistor.
          Good Luck to you,
          Tom
          yes, an open ten cent plate resistor in the PI, that's what it all was.
          The 82K one, I missed that one. It measured somehing like 22Mohms
          Thank you all.

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          • #20
            Well, after all this, now you know why a technician does *not* charge you 20 cents, although the only part replaced cost half that.
            All the time you were strongly suspecting a $100 Transformer (even $250 if it were some Mercury Magnetics jewel); worst of all is that it would *not* have solved the problem !!!!
            I think you owe Tom Philips and Louthud at least a sixpack each.
            Not me, because you *never* did measure voltage at the PI plates as suggested
            Juan Manuel Fahey

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            • #21
              Originally posted by JC@ View Post
              ... but I still think it could be the output transformer...
              The output transformer is defective if the amplifier is driven without a load (speaker)
              Check the output transformer, so the secondary attached to 6 to 10 VAC. The primary will get similar voltages between anode1 to +HT and anode2 to +HT. Amplifier is disconected from the "wall"
              Last edited by vintagekiki; 09-01-2010, 10:32 PM.
              It's All Over Now

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              • #22
                Originally posted by J M Fahey View Post
                Well, after all this, now you know why a technician does *not* charge you 20 cents, although the only part replaced cost half that.
                All the time you were strongly suspecting a $100 Transformer (even $250 if it were some Mercury Magnetics jewel); worst of all is that it would *not* have solved the problem !!!!
                I think you owe Tom Philips and Louthud at least a sixpack each.
                Not me, because you *never* did measure voltage at the PI plates as suggested
                If I had to return every bit of help I received in this forum after all this time I better go and stablish my own brewery.
                YES, it is a shame for me I didnīt check voltages at the PI plates. A real pity. Another six pack I owe.
                Said, thank you all, one more time.

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                • #23
                  Originally posted by vintagekiki View Post
                  The output transformer is defective if the amplifier is driven without a load (speaker)
                  Check the output transformer, so the secondary attached to 6 to 10 VAC. The primary will get similar voltages between anode1 to +HT and anode2 to +HT. Amplifier is disconected from the "wall"
                  I tend to jump from one point to another without method when I find something different. At least this time I measured resistance and voltage from both 'halves' of the primary. But earlier this year I had two amps showing very similar behavour and scope traces in the PI and it was a shot output transformer in both cases.

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                  • #24
                    JC,
                    Thanks for posting the resolution. I've been wondering how this was going to turn out.
                    Tom

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                    • #25
                      Agree, that was good, most of the time the "helped" disappears and we are left in the dark.
                      After all, *we* are guessing, we don't have the sick amp actually in our benches.
                      Many times we don't know if the owner just gave up (I think quite a few do) or which of the offered solutions was the right one in that particular case.
                      Juan Manuel Fahey

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                      • #26
                        Originally posted by JC@ View Post
                        I tend to jump from one point to another without method when I find something different. At least this time I measured resistance and voltage from both 'halves' of the primary. But earlier this year I had two amps showing very similar behavour and scope traces in the PI and it was a shot output transformer in both cases.
                        By measuring the resistance of the primary is not going to notice defective transformer.
                        It's just a short circuit between two adjacent winding primary, so that the output transformer is defective.
                        Inverse relationship between the measurement of transformation (from secondary to primary) is infallible. Any short-circuit can easily be discovered because it disturbs the relationship between transformation.
                        For a quick test can serve mains transformer than 6.3 VAC has two symmetrical HV windings. For example, 2 x 110VAC (a main transformer primary) to 2 x 180 VAC (a main transformer secondary). In test, HV windings used as primary, and 6.3VAC winding use as secondary (Speaker)
                        It's All Over Now

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                        • #27
                          Fixed my Super too! Same symptoms, same 82K bad resistor - cell lamp question

                          Yup, same problems on my amp and same bad component - 40 cent resistor!

                          Since I'm in here I'm going to replace the output tubes, it has been at least 5 yrs of working this thing hard

                          I do have a question for anyone that has an opinion on the vibrato cell lamp. I can see how small and cheap it looks, would replacing it for a better component make the vibrato better? As you know, the vibrato on these is not all that. My 62 Fender Concert on the other hand and has the best vibrato I've ever heard, sounds more like a vintage univibe, if you've heard these you know what I mean.

                          I do like the way my super sounds and it works great for me as my main gigging amp, but if I can make it better why not? right?

                          Thanks all!
                          -Ruben

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                          • #28
                            The old concert amp uses a very different vibrato design- not sure if your 62 is one of those or not.

                            You might modify your super to use a bias vary trem instead of the optocoupler trem- this can be done somewhat easily and the bias vary trem has a good sonic reputation.

                            jamie

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                            • #29
                              Thanks Jamie.

                              I should include here that I am not a tech by any means, though I'm good with a soldering iron and can use a MM my knowledge is limited and I work on my own gear out of necessity.

                              Having said that, I understand that this would involve controlling the bias of my output tubes for the effect. Meaning also that I would probably need to bias these "cold" to leave room for the vibrato. Would you care to provide some details on what would be involved and steps for this? Any advise is appreciated.

                              Thanks again
                              -Ruben

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                              • #30
                                I think you've got the basic idea of it. Look for a schematic that is built the way you want to head and start planning what you'd have to change. If you're short by a triode for the cathode follower in some trem designs just sub a high voltage mosfet in its place. I'm sorry I can't give more specifics right now- no time at the moment. There are plenty of threads out there on the various parts of a mod like this but I don't know of any one thread that says it all.

                                jamie

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