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Peavey 6505+ Amp turns on, no sound, power tubes don't light.

Discussion in 'Backline' started by Karg, Mar 10, 2010.

  1. Karg

    Karg New Metal Member

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    I went to turn on my Peavey 6505+ yesterday, and I waited for everything to warm up. I heard no sound coming from my amp for a while, so I checked all my cables. Everything was plugged in. I checked the power tubes and none of them were lit up. I removed the plate that covers the preamp tubes and 4 out of 6 of them are lit, I am not sure if they are all supposed to be lit or not. I checked the main fuse, and the 5 other fuses inside the amp and they are all fine. I have had the stock Ruby tubes since I bought the amp new about 2 years ago. I was thinking about going out and buying some new ones to see if that will fix the problem, but I don't think it will since all of the old tubes were working fine the day before, with no signs of them giving out at any time. Maybe one of the tubes died and the rest don't light because of it. I am not sure what to do. Any help is appreciated, thanks.
     
  2. TheWinterSnow

    TheWinterSnow Den Mørke Natt

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    You most likely had a fuse blow somewhere. And most lkely the two pretubes not lighting up could be the result of blowing power tube taking out some fuses (and power resistors).

    Get a Multimeter and test the fuses.
     
  3. Karg

    Karg New Metal Member

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    All the fuses look fine, and I used a little tool to check them and they all passed. How would I check the power resistors?
     
  4. Harry Hughes

    Harry Hughes   ‬‬

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    Equipment section
     
  5. SocialNumb

    SocialNumb Damn Christians!

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    Hold the phone! "Join Date: Jul 2007" and only 3 post?
     
  6. El_Gato

    El_Gato I love this gain

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    lul, once a year, not that bad
     
  7. 53Crëw

    53Crëw Member

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    If it's not a fuse, I'd guess something failed inside the amp. The odds of multiple tubes failing at the same time is pretty slim. ;)

    Perhaps a component related to the heater supply voltage went bad, or a bad solder joint failed somewhere...

    Really, someone needs to check the voltage supplies when the amp is turned on, and then when the standby switch is switched out of standby to see what is going on. Once you know what's happening at the power tubes in terms of voltage, you can isolate it further.
     
  8. Omega_Void

    Omega_Void Your Eventual Destroyer

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    I'm not familiar with the specific circuitry in 6505, but...

    Yeah, it's pretty much certain that the tubes should all be lit -- if there's no current in the heaters they won't do anything. And it takes too long to warm them up for switching out the heaters on unused stages to be practical.

    The tubes themselves are probably okay.

    In pretty much all amps, the hearters are wired in parallel, so if one heater filament fails and goes open it won't take the rest out.

    And if one filament fails as a short it would blow a fuse, or melt the power transformer' s low-voltage secondary or both, which would remove heater current from all the tubes.

    The fact that several of the tubes are lit and several aren't suggests an interruption in the wiring somewhere between the various sockets. Are the tubes which aren't lit are on a separate circuit board from the ones which are?

    Look for a bad solder joint, a cable or jumper wire come loose etc...
     
  9. Wolfeman

    Wolfeman I Prefer EL-34s. So What?

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    The reason for this is because a few of the tubes run off of a DC heater supply. There is a fuse for each type of heater, so if one goes some will still be lit up and the others won't.

    Most of the time with an issue like this, it's a blown fuse caused by a bad preamp tube. So change the tubes also unless you want the issue to happen again.
     

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