Is this a fuse? (and should I replace it...)

Discussion in 'General Electronics Chat' started by CurlsOnKeys, Apr 14, 2016.

  1. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
    47
    2
    Hi all,

    simple question. USB-connector of my MIDI-controller broke off, decided to try give it a shot and replace it with a new one.
    Desoldered the old connector, soldered on the new one, but unfortunately USB-midi (and USB-power) still didn't function.

    Upon further inspection, I noticed that two components appeared to be "missing" somehow. Maybe I applied to much heat during desoldering, maybe they we're never there, I don't know, anyway, they're gone. Talking about FP2 and F1 on the picture.
    My guess is that these "F" things are fuses, correct?

    I see them on every (yes, every) input/output pin on the CPU-board. So all four USB-pins are connected to an F (or FP) SMD. There are also regular old fashioned MIDI-connectors (5-pin-DIN), some TRS-audiojack-connectors: all pins of those connectors are attached to an F-type thing. A fuse, I guess. Is it really necessary to fuse every input/output connection? And so: should I replace those missing fuses? But what should there mA-rate be, they're not marked and I don't have the schematic? Or can I simply connect them through a simple wire and pray all goes well? :)

    Thanks!

    image_11.jpg
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    Look like fuse protection blocks, if there's no markings on them, jumper them out with wire.
     
  3. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
    47
    2
    Thanks for your help! So what's their use then? Or are they (most of the time) simply there because of regulations and design rules (as I read somewhere else?)
     
  4. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    for protection to the pcb from the outside world.
     
  5. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
    47
    2
    So no more protection than on those 2 pins? :) Well I guess it's either that or a non-functioning device anyway, so I'll take your advice and jumper them out.

    Thanks. In return I'll shout a bit harder to my tv-set to try and get The Reds to make 3 more goals :)
     
    Dodgydave likes this.
  6. BReeves

    Member

    Nov 24, 2012
    412
    64
    I wouldn't jump at just shorting them.. Could very well be just alternates to F2 and FP1, I would see if the two components have any pins in common and check F1 and FP2 for continuity. I'm not sure what FP1 is maybe a fuse maybe not.
     
  7. CurlsOnKeys

    Thread Starter Member

    Jan 3, 2015
    47
    2
    No pins in common and no continuity between fuses. 4 pins on the USB-connector, connected to four fuses. FP1 goes to ground, FP2 to C15, F2 to R3 and F1 to R2.
     
  8. ian field

    Distinguished Member

    Oct 27, 2012
    4,413
    782
    If the FP was the other way round, I'd throw a wild guess at polyfuse.
     
  9. RichardO

    Well-Known Member

    May 4, 2013
    1,230
    382
    I am guessing that F1 is a ferrite filter for EMI suppression. Jumpering that would not do any electrical damage but your AM radio (etc.) may quite working from the added interference.

    FP1 anbd FP2 are "big" devices and have "wide" traces to the connector. I am, again, guessing that they are also EMI filter ferrite. They and the traces are large because they are on the power and ground pins.

    You can verify the F1 and F2 parts connect to the signal pins and that FP1 and FP2 connect to the power pins on the connector using an ohmmeter.
     
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