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ENGL Thunder 50 problem

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  • 29-06-2006 6:35pm
    #1
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭


    I'm getting a horrible noise from my amp, a loud, very bassy hum. It seems a lot worse on the clean channel than the lead, but it's there on both. This has been happening for a while, but it used to go away if I left the amp in standby for about 10 mins. Now it always does it no matter what. I assume it's the tubes, but how the hell will I know which ones to replace?


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    #2
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Try turn on the amp, and tap on the tubes one at a time. That should tell you if any of them are microphonic, and you'll know which ones to change.


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    #3
    Kenny_D
    Registered Users Posts: 3,204 ✭✭✭Kenny_D


    Karl Hungus wrote:
    Try turn on the amp, and tap on the tubes one at a time. That should tell you if any of them are microphonic, and you'll know which ones to change.

    With your finger? Is that safe? lol


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    #4
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    A pen!

    Yeah nothing I noticed. Bear in mind this noise is REALLY REALLY bassy, not squealing.


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    #5
    Kenny_D
    Registered Users Posts: 3,204 ✭✭✭Kenny_D


    Try another instrument cable if you have one, or maybe its the pickups. Have you got a second guitar to try through the amp?


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    #6
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    It's 100% the amp, the guitar doesn't even need to be plugged in.


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    #7
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    A pen!

    Yeah nothing I noticed. Bear in mind this noise is REALLY REALLY bassy, not squealing.

    Did you try the preamp tubes aswell as the poweramp tubes?

    It does sound like tube issues, so if you can't single out a single tube as the problem, your best bet is to just replace the lot.


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    #8
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    Yeah i tapped them all. I'm gonna price out some tubes. Anyone recommend any ECC83 Preamp / 5881 Power Tubes?


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    #9
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    Yeah i tapped them all. I'm gonna price out some tubes. Anyone recommend any ECC83 Preamp / 5881 Power Tubes?

    Well, you probably know that I'm going to recommend a matched set from EuroTubes. Give Bob there an Email, and he'll sort you out will a full matched set for half the price you'd pay Thomann. I really recommend those tubes.


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    #10
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    That website confuses the crap outta me ;)


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    #11
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    That website confuses the crap outta me ;)

    Here the shop page.

    Email Bob at eurotubes@cnnw.net and he'll match up a set for you easy.


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    #12
    feylya
    Moderators, Music Moderators Posts: 23,359 Mod ✭✭✭✭feylya


    Have you gotten any new applicances in the house recently? Fridge, something like that?


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    #13
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    Hmm, would I get stuck at customs for any of that?

    No Feylya. It's happened in other houses awelll. It's a pain in the arse :(


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    #14
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    Hmm, would I get stuck at customs for any of that?

    Probably not. It wouldn't be much anyway if you did.


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    #15
    Eoin Madsen
    Registered Users Posts: 2,117 ✭✭✭Eoin Madsen


    Turn on the amp with each valve removed, one at a time, starting with the 5881s. When you remove the bad one, the hum will be gone. If it's one of the power valves, you'll need to replace the whole set anyway.

    Best not to play through it while there's valves removed though.


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    #16
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Eoin Madsen wrote:
    If it's one of the power valves, you'll need to replace the whole set anyway..

    Why's that?


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    #17
    feylya
    Moderators, Music Moderators Posts: 23,359 Mod ✭✭✭✭feylya


    Matched set/fixed bias?


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    #18
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    feylya wrote:
    Matched set/fixed bias?

    Oh right. Duh tbh.


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    #19
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    When I remove any of the preamp ones, the buzzing stops ...


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    #20
    feylya
    Moderators, Music Moderators Posts: 23,359 Mod ✭✭✭✭feylya


    Another problem solved :D


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    #21
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    Yay I'll play without any preamp tubes. But seriously, does that mean they are all damaged? or what?!

    :(


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    #22
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    Yay I'll play without any preamp tubes. But seriously, does that mean they are all damaged? or what?!

    :(

    Not really, could just mean it's old/worn out. Stock tubes in general aren't great.


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    #23
    Eoin Madsen
    Registered Users Posts: 2,117 ✭✭✭Eoin Madsen


    Try and look at it systematically. The speakers are connected to the OT which is connected to the power valves, which are in parallel, for all intents and purposes. The phase inverter and preamp valves are in series. With nothing plugged into the amp, all you're getting is internal noise being amplified from valve to valve. If you pull the second preamp valve, you cut the valve before it out of the circuit as well.

    If you know that a single one of the power valves isn't causing the hum, you can assume for now that the problem is in the preamp. So you need to eliminate the various preamp valves by swapping them around, such that you've removed each one in turn, but the only empty valve socket you use is the first one. If there's no hum for any of them, but there's always the same amount of hum when they're all in no matter which one is in the first socket, then you can probably move on to the assumption that the problem is not the valves.


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    #24
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    Ok, going by your advice about how they are in serial. I took them out in a particular order. Now taking out v2, stops the hum. So does v3 and v4 then obviously as they are in serial. Taking out v1 on its own still leaves a hum leavin V2 as our culprit **** Yeah ;)

    Maybe I should read up on my electronics again. I always told myself I would forget about it after I finished my course!

    Thanks Eoin and ze rest.

    Oh and in case you were wondering V1 was bitch to get out, hence me not trying it on its own. Yes I'm a moron.

    I've ordered a replacement, but I'm going to replace the lot when I get paid.


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    #25
    Eoin Madsen
    Registered Users Posts: 2,117 ✭✭✭Eoin Madsen


    Did you establish for definite that it's the valve and not something else in the stage? Swapping the valves around is important to be sure of that.


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    #26
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    I swapped them around, took out the ones before the one i thought was faulty, still buzzes. Took out the faulty one and replaced all the other ones, no buzzing. So i'm pretty sure it's just that the tube was faulty.


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    #27
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    New tube arrived! All better YAY!


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    #28
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Giblet wrote:
    New tube arrived! All better YAY!

    Yay for tubes! What brand did you go for?


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    #29
    Giblet
    Registered Users Posts: 11,977 ✭✭✭✭Giblet


    I just did a direct replacement with the same type until I get money for a full set at the end of the month. It has a bit more growl now, I think the tube was always damaged.


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    #30
    Karl Hungus
    Closed Accounts Posts: 29,130 ✭✭✭✭Karl Hungus


    Ah fair enough. ;)


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    #31
    david
    Registered Users Posts: 3,684 ✭✭✭david


    Go with eurotubes when you do a full revalve


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