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General question about Filter caps

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  • #1

    General question about Filter caps

    I'm curious what could happen if filter caps are not replaced if they're really old. Worst case scenario please.
    The Bias filter caps I know if they fail loosing bias is bad , but what happens?

    Thanks,
    nosaj
    soldering stuff that's broken, breaking stuff that works, Yeah!
    Tags: None
  • #2
    If your B+ caps dry out, they lose their ability to filter, and the amp gets hummy. The worst case would be cap failure in shorted mode, which would blow fuses.
    Education is what you're left with after you have forgotten what you have learned.

    Comment

    • #3
      Originally posted by Enzo View Post
      If your B+ caps dry out, they lose their ability to filter, and the amp gets hummy. The worst case would be cap failure in shorted mode, which would blow fuses.
      So it wouldn't affect the transformer at all? Some reason I was thinking failing filter caps would cause PT to get hot.

      nosaj
      soldering stuff that's broken, breaking stuff that works, Yeah!

      Comment

      • #4
        Since you asked about bias supply, well... hopefully you notice the amp humming loudly and sounding distorted as the output tubes begin to draw more current and overdissipate. If you miss that cue, they overheat and various things start to melt. Expensive things. Like tubes and transformers and chokes. There are some pics on the web of output tubes that lost their bias...

        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 -

        Comment

        • #5
          Originally posted by Justin Thomas View Post
          Since you asked about bias supply, well... hopefully you notice the amp humming loudly and sounding distorted as the output tubes begin to draw more current and overdissipate. If you miss that cue, they overheat and various things start to melt. Expensive things. Like tubes and transformers and chokes. There are some pics on the web of output tubes that lost their bias...

          Justin
          Good to know cause that's not something I want to gain experience with.

          Thanks,
          nosaj
          soldering stuff that's broken, breaking stuff that works, Yeah!

          Comment

          • #6
            Originally posted by Justin Thomas View Post
            Since you asked about bias supply, well... hopefully you notice the amp humming loudly and sounding distorted as the output tubes begin to draw more current and overdissipate. If you miss that cue, they overheat and various things start to melt. Expensive things. Like tubes and transformers and chokes. There are some pics on the web of output tubes that lost their bias...

            Justin
            Ok for some reason my Google-Fu isn't working to find pics of tubes that lost bias.

            Can you spot me some Fu for pics?

            Thanks,nosaj
            soldering stuff that's broken, breaking stuff that works, Yeah!

            Comment

            • #7
              The GE-6550A, and The Fender 400 PS Amplifier. A most Amazing Amplifier!!!

              That should do it... not sure if those are failed bias, but they're definitely melted! Having melted a tyranny, even looking at a picture of one brings the smell back... Bluh!

              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 -

              Comment

              • #8
                Originally posted by Justin Thomas View Post
                The GE-6550A, and The Fender 400 PS Amplifier. A most Amazing Amplifier!!!

                That should do it... not sure if those are failed bias, but they're definitely melted! Having melted a tyranny, even looking at a picture of one brings the smell back... Bluh!

                Justin
                Dang can you imaging carrying one of those amps?
                soldering stuff that's broken, breaking stuff that works, Yeah!

                Comment

                • #9
                  Meh, I lug my 86lb 2x15"...
                  "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 -

                  Comment

                  • #10
                    Originally posted by Justin Thomas View Post
                    Meh, I lug my 86lb 2x15"...
                    That 400 was just 85lbs for the chassis.
                    soldering stuff that's broken, breaking stuff that works, Yeah!

                    Comment

                    • #11
                      Peavey Classic 400 tube bass amp - 93.6 pounds. 400 watts (420 at clipping) Big heavy iron.
                      Education is what you're left with after you have forgotten what you have learned.

                      Comment

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