Laney AOR resistor question

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by ComingApart, Jul 1, 2006.


  1. ComingApart

    ComingApart Member

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    May 23, 2006
    Location:
    Louisiana
    Can anyone help me identify the purpose of the burnt resistor in the photo?
    The amp is a Laney AOR Pro Tube Lead 50watt head. I was having an issue were the amp would momentarily suffer from a reduction volume. I pulled the chassis and found the burnt resistor, I resoldered the point on it and it seems to have corrected the problem, but I thinking that there is a larger problem that just replacing the resistor won't fix.
    Any help I can get with his would be appreciated. I can't find a schematic for this amp.
    The resistor meters as a 1K and is tied to a leg of the large cap next to it.
    Sorry about the large pic.
    [​IMG]
     
  2. samwheat

    samwheat Member

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    Aug 14, 2005
    Location:
    Scranton, PA
    i have a schematic

    email me at bsjm2ATmsnDOTcom

    put laney in the subject message
     
  3. shooto

    shooto Supporting Member

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    May 15, 2006
    Location:
    Denver, CO
    man, that happened to my AOR 50 series II- I had a tube that was arcing too...don't know if the two were connected- my amp guy moved the little burn component off the board and threw in some new Sino EL34's...it's a monster now-
     
  4. John Phillips

    John Phillips Member

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    I can't remember for certain, but I think that resistor is the first B+ chain drop resistor. It basically goes in the circuit in the same place as the choke would do on an amp which has one (I don't remember if this one does or not). If so, all the current to the preamp and to the power tube screens goes through it, and it will run hot - especially if a power tube shorts or draws too much current via the screen (like shooto's arcing tube).

    It's not good design to mount it so close to the circuit board - the problem is not that the resistor has actually burned out, just that it has cooked the board and desoldered itself. Every tech in the world sees this problem on a regular basis :).

    One solution if the board isn't too damaged is to fit standoff posts and get the resistor much further away from it, but much better is to fit a chassis-mounted tag strip somewhere else and put the resistor there.

    You may even find that electrically the resistor is connected between the two large filter caps, in which case you could simply put it there physically as well.
     
  5. ComingApart

    ComingApart Member

    Messages:
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    Joined:
    May 23, 2006
    Location:
    Louisiana
    I'll get a ceramic resistor and mount it off-board.
    It's nice to find a board with some tech-minded folks. Ya'll (yes, i said "ya'll")
    have been a huge help and I look forward to learning as much as I can from here.
    A huge thanks to those who responded.
     

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