Figuring out which fuse is which

Discussion in 'General Electronics Chat' started by nimitj, Jul 20, 2017.

  1. nimitj

    Thread Starter New Member

    Jul 20, 2017
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    0
    Hi All,

    I have a DAC Card for a sound system that stopped working. I was quickly able to work out that 1 fuse and 5 caps had gone. I've replaced the caps, but am unable to find any schematics for the board to work out what the fuse it.

    All I know is the board has 4 fuses. (F1 - F4), the tech spec sheet gives the followings:

    +3.3 V DC, ±0.3 V / 140 mA
    +5 V DC, ±0.25 V / 190 mA
    +18 V DC, ±0.5 V / 270 mA
    -18 V DC, ±0.5 V / 160 mA

    Any help anyone can give me would be amazing. The product itself is the Electro-Voice AO-1.

    Thanks
    Nimit
     
  2. JUNELER

    Member

    Jul 13, 2015
    181
    25
    Hi,
    Your F1-F4 are small values. So you can use up to 500ma to test what you are confuse even without schematics.
     
  3. nimitj

    Thread Starter New Member

    Jul 20, 2017
    3
    0
    I forgot to add, the fuse is Green and has a small F on it, the size is around 1.6mm length by 0.8mm wide
     
  4. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    5,395
    1,196
    So do we assume that F1 = the 140mA fuse and F2 = 190mA and F3 = 270mA and F4 = 160mA ?
    If so can't you read the reference designators on the board to identify each one?

    Or do you know which fuse is blown and you are just asking for us to find the proper replacement part number?

    Sounds like they are poly resettable fuses in the 1608 SMT package.. But thats it..
    F might be LF for littelfuse or F for Ferraz Shawmut or even just F for fuse from Bussman/Eaton,etc...
     
  5. MrChips

    Moderator

    Oct 2, 2009
    17,376
    5,366
    With power applied, take a voltmeter and measure the voltage at the fuse (try both leads of the fuse) with respect to GND. This will tell you which fuse is which.
     
  6. JUNELER

    Member

    Jul 13, 2015
    181
    25
    Hi,
    Dont mind the color(its a housing with a wire inside -fuse) and since it is dc is little bit safe.
     
  7. nimitj

    Thread Starter New Member

    Jul 20, 2017
    3
    0
    ---

    According what info I can get from the tech specs and speaking to Bosch.

    F1 = +18v
    F2 = -18v
    F3 = +5V
    F4 = +3.3V

    I know F3 has blown this shows as open when measured. I'm kind of after a little advice on what might be a suitable replacement. Not so much someone finding it for me, just some direction.

    Thanks
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    5,395
    1,196
    Ok...So you need a 190mA rated polyfuse in a 1608 SMT package..
     
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