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'PF' designation for raised resistor

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  • 'PF' designation for raised resistor

    Working on a GL series Allen & Heath mixer. A few resistors are stood off from the circuit board, they are marked PF on the schematic to designate this.
    Just curious as to what the PF is an abbreviation for. (in supply rails for headphone amp)
    "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

  • #2
    Maybe they meant FP as in flame proof? Misprint?
    "Yeah, well, you know, that's just, like, your opinion, man."

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    • #3
      I had thought that too. But they have the exact same parts elsewhere that are not stood off and no schematic designation. And they look like very standard resistors.
      "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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      • #4
        Phenolic resin coating?
        https://link.springer.com/article/10...209-009-0050-1

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        • #5
          If you are refering to R90-93 & R97-100 they are fire proof just in case of numpties plugging something silly into the headphone socket and killing the headphone output transistors. And yes, it has happened!
          Support for Fender, Marshall, Mesa, VOX and many more. https://jonsnell.co.uk

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          • #6
            Are the leads on those resistors formed to maintain their height above the board? Maybe "pre-formed"?

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            • #7
              Hey, I like that one.^^^^
              Education is what you're left with after you have forgotten what you have learned.

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              • #8
                Originally posted by Greg Robinson View Post
                Are the leads on those resistors formed to maintain their height above the board? Maybe "pre-formed"?
                I thought on it. But all I came up with was "probably fine". I'm going with "pre formed" though.
                "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

                "Being born on third base and thinking that you must have hit a triple is pure delusion!" Steve A

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                • #9
                  Originally posted by Greg Robinson View Post
                  Are the leads on those resistors formed to maintain their height above the board? Maybe "pre-formed"?
                  Pre-formed seems to be it. The leads are kinked to stand them off the board a few mm.
                  Jon Snell , they are definitely not special 'flame-proof' type, but they are stood off the board to perform that function (for reasons you mentioned). GL2200, R33-36, R107 & R108.
                  "Everything is better with a tube. I have a customer with an all-tube pacemaker. His heartbeat is steady, reassuring and dependable, not like a modern heartbeat. And if it goes wrong he can fix it himself. You can't do that with SMD." - Mick Bailey

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                  • #10
                    PF as pre-formed sounds very reasonable. While these aren't a necessity, I do have and use a set of these to make nice, consistent lead forms.

                    https://hakkousa.com/chp-pnr-30-d-lead-forming.html

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                    • #11
                      Those lead formers are nice. Saves playing around with needle-nose pliers.

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