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resistor symbols

Discussion in 'Troubleshooting and Repair' started by looxuser, Jan 11, 2016.

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  1. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    hi, i have circuit diagram for an amplifier im trying to repair. most resistors are shown as a zigzag line but there are some that appear as a zigzag line bounded within a rectangular box. what does this mean please?
     
  2. Colin Mitchell

    Colin Mitchell

    1,417
    312
    Aug 31, 2014
    It could mean a safety resistor or a thermal resistor
     
  3. Minder

    Minder

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    640
    Apr 24, 2015
    It is extremely rare for a combination of both resistor symbols either post the application or a clearer picture of the resistor, there is usually other indication if a specialized function.
    M.
     
  4. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    centre you'll see a rectifier,right of that is an over current detect cricuit which i think is holding my off my amplifier producing anything but a small volume output. within that circuit you can see four resistors mentioned bordered by a rectangle, yet others in the circuit diagram do not have this. left of rectifier you can see FR501 which has a symbol for a fusible resistor. In summary three types shown here two obvious but what i can;t undertsand is if the bordered resistor symbols indicate, safety / thermal resistor why they wouldn't have used that symbol convention throughout. Any help appreciated.
    upload_2016-1-11_21-53-53.png
     
  5. looxuser

    looxuser

    77
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    Dec 28, 2015
    this may be better to see... upload_2016-1-11_22-1-0.png and upload_2016-1-11_22-1-34.png
     
  6. Minder

    Minder

    3,013
    640
    Apr 24, 2015
    The FR502 is a fuse or current limit resistor what do the R526 R530 appear to be in pysical appearance, they may be just WW resistors.
    M.
     
  7. looxuser

    looxuser

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    Dec 28, 2015
    the turquoise ones shown here.. 2016-01-11 22.34.55.jpg Minder they are .
     
  8. davenn

    davenn Moderator

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    1,891
    Sep 5, 2009
    They ( R525, 526, 529 and 530) are just standard fusible resistors nothing overly rare about them ;)
    FR501 .. isn't in the bit of circuit you posted ... It really is a fuse and if you look closely through the
    glass envelope you will also see an incorporated resistor, a fancy kind of slow blow fuse

    Dave
     
    Last edited: Jan 12, 2016
  9. looxuser

    looxuser

    77
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    Dec 28, 2015
    Thanks Dave they are marked R22J 1w fyi
     
  10. davenn

    davenn Moderator

    13,669
    1,891
    Sep 5, 2009
    yes, R525, 526, 529 and 530 are 0.22 Ohms and 1Watt
     
  11. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    HI there, this is FR501 removed and tested open circuit. its actually light blue in colour with bands grey red black gold which i've determined is the 82r 1/2w fusible 5%. I read somewhere light blue means fusible
    but could that be right i wonder, perhaps the ones that look turquoise are really supposed to be light blue in colour also again indicating fusible albeit they are not banded but marked.
    2016-01-12 17.11.49.jpg
     
  12. looxuser

    looxuser

    77
    2
    Dec 28, 2015
    Ok guys i discovered what the zigzag surrounded by a rectangle represents by comparing to other circuit diagrams i found online. Infact this means the resistor is marked not banded to represent its value.
     
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