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5E3 blown resistor

Discussion in 'Amp Tech Center' started by xjazzy, Oct 3, 2014.

  1. xjazzy

    xjazzy Friend of Leo's

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    I have a slightly modded 5E3 that I was going to sell cause it's been on the shelf for a while and when I fired it up one of the resistors started smoking!
    Replacing the power tubes all started working correctly but I need to replace the resistor.
    The problem is the blown one is a 470ohm resistor and all the diagrams show 4.7K or 5K resistor!
    Could this be due to the modded circuit?
    Is it safe to replace with a similar one?

    It's the resistor that connects the last two big caps on the left of the board:

    [​IMG]
     
  2. printer2

    printer2 Poster Extraordinaire

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    Put in a 4.7k resistor, having a 470 ohm one in that position is almost like having no resistor there at all.
     
  3. mherrcat

    mherrcat Tele-Holic

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    I can't answer your question, except to say most of those resistors I have seen on the filter caps are metal oxide, not carbon film; the one on the right appears to be metal oxide. Don't know if it really makes a difference.

    But the reason I responded is this: It is probably an optical illusion of the photo, but that speaker plug and the center contact on the external speaker jack look really close to the leads on those caps!
     
  4. xjazzy

    xjazzy Friend of Leo's

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    Ahah, it's optical ilusion.

    But what's the benefit of having that resistor with higher or lower value?
    What does it do?
     
  5. Wally

    Wally Telefied Ad Free Member

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    xjazzy, as shown in the schematic that is the dropping resistor for the voltage feed to the screens. IF you want to do some experimenting and learn through doing, install a fresh 470 ohm and take voltage measurements...plates and screens on the 6V6's, plates on all of the 12A_7's. Play and listen well. Then, install a 5K and take those measurements. Play and listen.
    You might decide to keep the amp.
     
  6. Wyatt

    Wyatt Tele-Afflicted

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    Dropping resistor, that particular one drops the voltage between the power tube plates and power tube screens (and everything downstream...PI and preamp). The next one (22K) drops the voltage further before it goes to the PI and preamp.

    EDIT: beat to the punch
     
  7. mherrcat

    mherrcat Tele-Holic

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  8. xjazzy

    xjazzy Friend of Leo's

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    Thanks.
    I have another 5E3 that is more true to the original circuit and I'm gonna keep that one.
     
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