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Thread: Okay, this is odd....

  1. #1
    Supporting Member Randall's Avatar
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    Okay, this is odd....

    Guy brings me a SVT Classic head that he said died at a small venue gig. He said amp cut out, and when he looked at the cab, both he and another guy saw what looked like an orange glow coming from the top two speakers (4 x 10). Huh? I fired up the head and it came right on, bias LEDs were tight, no prodding or thumping noises. I left it on for 20 minutes with no symptoms and called him to bring me this orange glowing cabinet. I opened it up, it works and sounds fine, no evidence of anything overheating, no smell, no voice coil rub... Basically I could find nothing amiss. But, he swears the cabinet was glowing like it "had a string of LED lights in it."

    What can you say to a known knowledgable customer when what they are saying is hard to fathom? Strange indeed.

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    It's weird, because it WAS working fine.....

  2. #2
    Don't forget the joker g1's Avatar
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    No tweeter protection bulb in the cab?

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Old Timer J M Fahey's Avatar
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    Does the glowing cabinet have a Driver/horn/tweeter?
    YES/NO : tick one off.

    EDIT: simulpost with G1

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    Juan Manuel Fahey

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    Darn, I was going to guess ball lightning.

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    DON'T FEED THE TROLLS!

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    Old Timer J M Fahey's Avatar
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    Not sure which cabinet are you talking about, but you might find one of these inside:





    Can any component there create an orange glow?

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    Juan Manuel Fahey

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    So with a protection bulb on a tweeter what would make it fully light up and cause the amp to shut down? Shorted horn? Could the amp gone into a high frequency oscillation?

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    Don't forget the joker g1's Avatar
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    I think HF oscillation is a good candidate.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

  8. #8
    Bent Member Chuck H's Avatar
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    Well Randall hasn't chimed in on the matter yet. He did say "4 x 10". I hope there's a bulb protected tweeter in the cab after all though. If not then maybe someone was dosing the punch at that gig.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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    Supporting Member Randall's Avatar
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    I don't know if there is a bulb limiter in the cab, but there is a horn and attenuater, which I verified were working. Also, he said it was a low volume gig, so I don't really see why a bulb would light up enough to make two speakers glow in that situation. But, I do admit, I did not think of there being a bulb in there.

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    It's weird, because it WAS working fine.....

  10. #10
    Don't forget the joker g1's Avatar
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    glebert gave 2 reasonable suggestions as to why (in post #6). Also, I think if someone adjusted the attenuator, or if it were faulty (open), you may get bulb action that was not there previously.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

  11. #11
    Old Timer J M Fahey's Avatar
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    Also, he said it was a low volume gig


    Yea, sure

    They ALL say that, darling ....

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    Juan Manuel Fahey

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    Supporting Member The Dude's Avatar
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    Another possibility is a bad or intermittent shorted crossover cap causing full range audio to hit the tweeter circuit. That would certainly light up a protection lamp. If it's the case, you'll know soon with either a blown lamp or tweeter.

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    “Yeah, well, you know, that’s just, like, your opinion, man.”

  13. #13
    Lifetime Member Enzo's Avatar
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    Post #5 photos are typical. A handfull of screws and we can LOOK at the crossover assembly. That would seem to get to the bottom of this a lot faster than trying to solve it philosophically.

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    Education is what you're left with after you have forgotten what you have learned.

  14. #14
    Supporting Member Randall's Avatar
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    I would of course do that, but the amp and cab worked fine when it was here, so he didn't leave it. He says he will lean on it during some practice time, and we shall see what we shall see.

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    It's weird, because it WAS working fine.....

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