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Crackling noise (idle) Fender DR

Discussion in 'Amp Central Station' started by Dan Theman, Aug 23, 2014.

  1. Dan Theman

    Dan Theman Tele-Meister

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    I have a Fender Deluxe Reverb 72. After ca 10-15 minutes there is a crackling noise, very low, independent of volume and tone controls. I have read about it and I think it's the plate resistors. I think they are 100K, what do I replace them with? Any particular type of resistor?
     
  2. DaveKS

    DaveKS Friend of Leo's

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    Could also just be power tubes after they heat up. Or socket contacts need cleaned up re tensioning.
     
  3. seedlings

    seedlings TDPRI Member

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    It could be the Screen resistors on the power tubes 470 ohm to pin 4 (off of pin 6). As you say, it could also be the 100k plate resistors in the preamp. Try a 1/2 watt metal film resistor. Those are quiet compared to the carbon composition.

    I recommend you open her up, power on, get a wooden/bamboo chopstick and tap every component and every solder joint and EVERY GROUND POINT to see if one is flaky.

    CHAD
     
  4. Dan Theman

    Dan Theman Tele-Meister

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    How does it show? Or sound? When you hit one that is bad?
     
  5. Johnny Cache

    Johnny Cache Former Member

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    My first guess, a tube is arcing causing emission noise. Which you could fix just by replacing that tube(s), could be more than one. Second guess, loose tube socket(s). Try cleaning them and re-tighten them. Third guess, a resistor is out of whack.
     
  6. Dan Theman

    Dan Theman Tele-Meister

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    Do you mean preamp tubes? I have checked and replaced them with fresh ones. If you mean power tubes I guess I need to replace the pair.

    If those plate resistors are bad, does it show if I measure them or can they still be bad but show the right value on the meter?
     
  7. 10thoufirst

    10thoufirst Tele-Holic

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    I had a similar problem with my HR Deluxe. Went back to Fender who said they changed the valves (tubes). Been fine since.
     
  8. BobbyZ

    BobbyZ Doctor of Teleocity

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    It could just be a tube. A GV-22 Ampeg I got cheap because it made all sorts of noise turned out to be a bad 12ax7.
    (well that amp also needed a full set of electrolytic caps and so does your DR if it hasn't been done yet)

    Some of the silverface (maybe most) had 1 watt 100K grid resisters where the blackfaces had 1/2 watters. Either way out of the 7 Fender amps I've got here now all of them have the stock resisters.
    Other than a 65 BFTR that had the 470 screen resister changed by a tech in the Twin Cities that always seems to change them (but leaves old electrolytics?) the rest have all original resisters.

    Anyway I'd try some tube swapping first.
     
  9. Dan Theman

    Dan Theman Tele-Meister

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    I have recently replaced the electrolytics (under the metal cover).
    I have put fresh tubes in (all except the V6 Phase inverter that requires a 12AT7 (that I don´t have). But I put a 12AX7 in there instead temporarily and I think the noise was a bit lower (started after ca 15 min though)
    Also I measured all the plate resistors and they are between 101-104.5K (the 82K is 85.4K). I don't know if these values are within limits and the resitors could be considered OK?
     
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