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Kenwood KR-865G Burnt Resistor

Discussion in 'Datasheets, Manuals and Component Identification' started by KilgoreCemetery, Feb 19, 2018.

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  1. KilgoreCemetery

    KilgoreCemetery

    246
    13
    Apr 12, 2017
    I have a wire-wound resistor that is burnt beyond recognition and I'm hoping to find somebody that either has this exact model or has a service manual for this model so that I can figure out what value it's supposed to be. Unfortunately, It doesn't have a matching pair and the third band is just gone...
     

    Attached Files:

  2. FuZZ1L0G1C

    FuZZ1L0G1C

    366
    118
    Mar 25, 2014
    First two bands Red and Violet make it 27.....
    Third (multiplier) band unreadable.
    Fourth (Gold) band makes it 5% tolerance.
    The blue body means it's a metal film resistor, not wire-wound.
    The film is visible where multiplier band used to be.
    Comparing your needle-nose against resistor body dimension, it looks like 0.25 W power rating.
    Unfortunately, without the multiplier, it's anybody's guess whether value is 2R7, 27R, 270R, 2K7,etc.
    Your best bet is to refer to a schematic diagram, possibly available on line.
     
    KilgoreCemetery likes this.
  3. 73's de Edd

    73's de Edd

    3,232
    1,351
    Aug 21, 2015
    Sir KilgoreCemetery . . . . .

    Did I miss my burial ceremonies . . . or do you now have me rescheduled?

    Sooooooooooo . . . . lets just use the old hypothesis / to / tenet / to / axiom of :

    " Half of a resistor, is being better than no resistor at all. "

    First you didn't give . . .enoughly . . . info, as to the units circuitry use and location within the involved circuitry . . . plus the voltages involved across it.
    Unless high voltage is involved and the unit CERTAINLY is appearing to be of a spiral cut, deposited metal or carbon film, as was being used in its construction manner, we can start with a suspicion of a max of 27Ω or progressively lower,on down to 2.7Ω . . . . .or . . . . .0.27 Ω.
    (Wheeeeeeeeeeeeee I finally gots to use the ohmmie- thingee at the top of the page.)

    Pull out your DVM and twirl the meter leads plugs around multiple times within its banana jacks ? to clean and get the lowest ohmmic contact interfacing . . .and also to desensitize shifting any ohmmic connection as the test leads are moved around up near those connective junctions in testing. .
    Pull out an eraser and clean / deoxidize the contact area of the test leads tips in the areas that they will touch in making your ohms readings. Then, degrease any eraser gunk from the cleaned tips.
    Take the resistor and initially use a double clip lead to connect the ends of the resistor together.

    TESTING . . . . .
    One ohms lead goes to the now conjoined resistor lead ends.
    Even though the insulation / paint /ceramicover may now be somewhat devoid at the center of the resistor.
    A still preferred procedure would be to get a single edge razor blade that has the foldover aluminum strip covering its unsharpened half of the blade.
    That then is being a good contact area to use your other free test lead and pressure grip between finger and thumb to enact a good connection . THEN you do a microsraping of the resistance metal at MID POINT of the resistor. You should then get an ohms reading.
    Then you take the jumper clip loose from the ends and test from one lead end at a time to see which end is being involved in that closed circuit reading.

    Re take that resistance reading . . .log it . . . .then place the test tips together to thereby get the test lead and contact resistance. Subtract that from your prior 1/2 resistor reading and then double that resistance and see if you had a 27------2.7 or 0.27 ohm resistor.
    IN the RARE chance of not finding resistance, then work with the one third or one quarter of a resistor concept.

    BTW . . . if this is one of two resistors being used in the emitter circuits of a pair of 2SC2579 and 2SA1105 power output transistors . . . . make my final value as being a 0.27Ω @ 2 Watt metal film unit
    The " Needlenose Pliers " . . . . looks more like a set of surgical 6.5 in Rankin Crile hemostat forceps


    Thasssssssit . . . .

    73's de Edd
    .....
     
    Last edited: Feb 20, 2018
    KilgoreCemetery likes this.
  4. KilgoreCemetery

    KilgoreCemetery

    246
    13
    Apr 12, 2017
    FuZZ1L0G1C: Woops! You're right, it's not wire wound at all. I didn't know that the body color indicated type. Is there a complete list available somewhere? I'll be searching for that soon. Unfortunately, I haven't found a free copy of the schematic, but I'm considering buying one.

    73's de Edd: No burial ceremonies just yet. That amp was turning into a time vampire, and I have so many other fun projects to work on. I keep looking over at it and asking myself "Is today the day?" So far the answer has been no, but I have given myself a deadline.

    As for the resistor testing.. I didn't know you could do that!!! The short version is that I came up with a reading of 14Ω! I'm assuming I wasn't quite in the middle and that it is, indeed, a 27Ω resistor!

    If you want the longer version, it came from the pre-amp section of a Kenwood KR-865G receiver. It's in the middle of the left and right channel mirrored area, with no matching partner. I found it next to a swollen 63V, 47uF capacitor.

    I was told that the speaker wires were touched together while the unit was on. It took out the 2SA1186 and 2SC2837 on the left channel, along with a 2SA899 Silicon PNP transistor and the A1127 BJT next to it.
     

    Attached Files:

  5. FuZZ1L0G1C

    FuZZ1L0G1C

    366
    118
    Mar 25, 2014
    Resistor body coloring:
    AFAIK beige is carbon film and pale blue is metal film.
    Older carbon resistors were mostly dark brown bodies. Not sure if wire-wound (usually for high power resistors) has a specific body color code.
    The ones 10 W>25 W I've used in the past have been rectangular white ceramic, or resistor with white / pale grey / green bodies, the wound resistor wire 'bumps' usually just under the painted surface.
    Guessing it depends on manufacturer or factors such as temperature coefficient etc.
    The quickest resource for 'Resistor Body Colors' would be the web.
    Suggest Wiki or Google.
    Component distribution catalogs from Radio Shack or Maplin (etc) often contain 'information' tables or facts to aid in selecting products, some with photos of the product (thinking resistor bodies).
    Clive.
     
  6. KilgoreCemetery

    KilgoreCemetery

    246
    13
    Apr 12, 2017
    That's some awesome info! Thanks, FuZZ1L0G1C!
     
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