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Peavey 6505+ 112 blows main fuse

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  • #1

    Peavey 6505+ 112 blows main fuse

    Yet another project I purchased and on deck. This amp had a high resistance 3 AMP mains fuse and would not turn on. I put a new fuse in and the amp turned on. The two power tubes were glowing nomal. Once I turn the stand-by off there is a slight pop sound and it blows the mains fuse.

    I have not had time to open it up yet. I plan to pull all the tubes and test them sometime over the weekend. What are the general issues to look for in this scenario?

    Thanks again! Mark
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  • #2
    Start by pulling the power tubes.

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    • #3
      Yes^^^

      Test the tubes by simply pulling them and powering up the amp. If the fuse still blows when both switches are on, then it is not the tubes. If the fuse holds without tubes, you had a bad one.
      Education is what you're left with after you have forgotten what you have learned.

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      • #4
        It was bad output tubes. Thanks for the info because my tube tester told me both tubes were good, so I would have been looking in all the wrong places without the help.

        Why did my tube tester tell me they are both good? I am using a Mercury Model 1100. It tests for shorts and quality.

        Much thanks!

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        • #5
          Because it is a tube tester. No offense, I have one too, I never bother to get it out. All a tube tester can do it verify a bad tube is bad. It cannot tell you a tube is good, really. In other words, if your tester says a tube is bad, it probably IS bad. But if it says good, you cannot trust it. When people enter my shop and ask if I have a tube tester, I always say, "You're talking to him." Then we all chuckle. If I have reason to suspect a tube, it is far faster, and way more accurate for me to simply slip a new tube into the socket and find out.

          Tube testers can look for gross faults, and are useful for comparing emission tube to tube, but the voltages and currents the tester puts on the tubes are not real world conditions for the tube. Imagine working on cars, and to test drive all you did was drive up and down the length of your driveway. The car might drive that way just fine, but you'd never know whether the car was fine at highway speeds. It's like that.
          Education is what you're left with after you have forgotten what you have learned.

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          • #6
            Great info! Thank you!

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