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Weird Capacitors! Need help determining replacement value

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  • Weird Capacitors! Need help determining replacement value

    So I've never seen capacitors like this before, in fact I'm not even 100% sure they ARE caps. They're referenced as C on the circuit board along with some other known capacitors though, so I'm to believe they are capacitors. Unfortunately none of them measure any capacitance on my multimeter and I can't understand the markings to determine replacement values. I also can't find a schematic for this amp (Carlsboro solid state amp).

    Here's a picture:

    Click image for larger version

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    The values written on the capacitors are like "100 MN". Any ideas?

  • #2
    Do they measure any resistance? Model number? Problem you are encountering? If they are caps, I can't believe that many would be open, test known good caps with your meter, start at 100pf.

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    • #3
      Originally posted by mozz View Post
      Do they measure any resistance? Model number? Problem you are encountering? If they are caps, I can't believe that many would be open, test known good caps with your meter, start at 100pf.
      Known good caps measure accurately. These mystery "Caps" all measure OPEN for resistance. This amplifier was making a lot of noise (windy, popping, etc..) and I replaced all of the electrolytic capacitors - it's quieted down but I'm still getting some Popping. The popping isn't affected by the channel volumes or tone controls, but it does go away when the Master vol is turned down.

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      • #4
        Measuring a small value capacitor with your meter set to read resistance is pointless.

        Most caps will read open circuit.
        Electrolytic caps will show a reading as the meter voltage charges them up but this is not a valid test of the cap.

        If nothing else, go out and purchase a cheap meter that has a capacitance tester.

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        • #5
          I recognise those as caps, though can't recall the technology.
          The numbers are probably their value in pF
          My band:- http://www.youtube.com/user/RedwingBand

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          • #6
            They look like common ceramic caps to me. Common in a previous era, yes, but tube TV sets would be full of them. Numbers ought to be cap value in picofards.
            Education is what you're left with after you have forgotten what you have learned.

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            • #7
              Originally posted by Jazz P Bass View Post
              Measuring a small value capacitor with your meter set to read resistance is pointless.

              Most caps will read open circuit.
              Electrolytic caps will show a reading as the meter voltage charges them up but this is not a valid test of the cap.

              If nothing else, go out and purchase a cheap meter that has a capacitance tester.
              Hey JPB, I was measuring them in the capacitance setting but was responding to mozz who asked what they measured in resistance (presumably to see if they're something other than capacitors).

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              • #8
                I just mentioned resistance because he wasn't 100% sure they were actually a cap. If they are pf caps, why no meter reading? M could be tolerance 20% and then N stands for nano? Still doesn't answer why would they all be open. How old of a solid state amp? 1965? 1985?

                Here are some tube schematics, other page shows some of those caps even on the tube amp models, schematics call them 3kpf, 47kpf.

                Carlsbro Amplifier Vintage Wiring Diagrams
                Servicing a Carlsbro CS100 Reverb PA Amplifier

                Click image for larger version

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                Last edited by mozz; 09-02-2017, 09:43 PM.

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                • #9
                  Wonder if MN is milli-nano, which would be pico

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                  • #10
                    Originally posted by glebert View Post
                    Wonder if MN is milli-nano, which would be pico
                    Unless kpf is kilo-picofarad, which would be nanofarad.
                    DON'T FEED THE TROLLS!

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                    • #11
                      Does your meter cap setting normally measure down to small values like 50pF ?
                      Originally posted by Enzo
                      I have a sign in my shop that says, "Never think up reasons not to check something."


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                      • #12
                        milli-nano??? Now I have heard everything.
                        Education is what you're left with after you have forgotten what you have learned.

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                        • #13
                          Originally posted by Enzo View Post
                          milli-nano??? Now I have heard everything.
                          No Sir, you still need to listen to milli-vanilli

                          enjoy specially from 0:52 on
                          Juan Manuel Fahey

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                          • #14
                            MV... great, now my Master Volume knobs on my amps (built or bought) will be called the "Milli-Vanilli" knob. Because Milli-Vanilli and Master Volumes are equally criminal inventions foisted upon the world.

                            Juan, that was as horrible as it was 30 years ago when I had to hear it on the school bus. A pox on you for posting that! T-Boy, where's that "HULK SMASH!" button?

                            Justin
                            "Wow it's red! That doesn't look like the standard Marshall red. It's more like hooker lipstick/clown nose/poodle pecker red." - Chuck H. -
                            "Of course that means playing **LOUD** , best but useless solution to modern sissy snowflake players." - J.M. Fahey -
                            "All I ever managed to do with that amp was... kill small rodents within a 50 yard radius of my practice building." - Tone Meister -

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                            • #15
                              Ok, here´s the antibiotics to cure that ear infection

                              Juan Manuel Fahey

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