Replace 150 ohm 5w resistor on 2230 power supply

Discussion in 'Marantz Audio' started by runningdog, Sep 12, 2017.

  1. runningdog

    runningdog AK Subscriber Subscriber

    Messages:
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    Location:
    Sonoma, CA
    The square ceramic 150 ohm 5w resistor on a 2230 power supply can scorch the C804 electrolytic capacitor and the wire running to the collector of the outboard transistor. It is squeezed in-between these two items (this does not apply to the units that have the resistor mounted underneath).

    Is it OK to replace the square ceramic resistor with a more compact wire wound resistor such as this one?
    https://www.digikey.com/product-detail/en/ohmite/45F150E/45F150E-ND/823288

    I saw a post that described doing this, to increase the space between the resistor and the other components and provide for more air to flow between them. And I think it suggested a resistor like the Ohmite wire wound shown below. But I have not found the original post yet.

    Is a wirewound is an appropriate resistor for this purpose?

    ohmite 150 ohm 5w resistor.jpg 2230 P800 scorched capacitor.jpg 2230 P800 scorched wire.jpg
     
  2. whoaru99

    whoaru99 Epic Member

    Messages:
    38,185
    Location:
    LoTL
    Type of resistor aside, if it is the same value but physically smaller and used in the same circuit it will all but certainly run hotter.

    Whether the distance gained would offset that I can't say.

    Is that actually heat damage, or is it smoke/smudge from something else?
     
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  3. deltalight

    deltalight AK Subscriber Subscriber

    Messages:
    158
    Location:
    Minneapolis
    Yes, in several Marantz models, the original resistor will indeed scorch the PS board. I replaced the square cement resistor in a 2245 with a WW of the same WW round type you show. Make sure you mount the resistor off the board by crimping the leads or use teflon standoffs.
     
  4. whoaru99

    whoaru99 Epic Member

    Messages:
    38,185
    Location:
    LoTL
    Yeah, if one can use standoffs to increase distance that would help.

    But, in this case that doesn't look like heat damage it looks like smoke. I wouldn't expect heat damage to wipe off and it looks like that would and has to some degree already wiped off.
     
  5. Leestereo

    Leestereo Super Member

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    Ottawa, ON
  6. runningdog

    runningdog AK Subscriber Subscriber

    Messages:
    299
    Location:
    Sonoma, CA
    I was able to wipe off the black mark on the cap. When I first looked at it both the wire and the cap were close to or touching the resistor at the points with the black marks. Scorch or smoke? I'm not sure.

    Thank you, this is what I'm looking for.
     

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