Vox Night Train NT15H Head- noisy- need advice

Discussion in 'Amp Central Station' started by teleblastard6, Oct 17, 2019.

  1. teleblastard6

    teleblastard6 TDPRI Member

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    Bought a used Vox NT15H head [pawn shop prize] .Plays fine. Problem is, it's distractingly noisy. Not a single coil or 60 cycle hum issue. When I turn the pick-ups all the way off @ the guitar, the amp makes noise while in standby. Anyone know why?
     
  2. Dacious

    Dacious Poster Extraordinaire

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    It sounds like it's got a bad filter cap, depending on the standby switch location if it's a low thrumming hum. Could also be a bad ground connection, which might just be screw fitting.
     
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  3. teleblastard6

    teleblastard6 TDPRI Member

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  4. teleblastard6

    teleblastard6 TDPRI Member

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    Wow! Bad filter cap was an idea I had, but I don't know jack 'bout amp repair. What do you mean by 'screw fitting' ?
     
  5. Dacious

    Dacious Poster Extraordinaire

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    Often they're
    There might be a shield on the transformer, or a ground lead off the board screwed through a serated washer onto the chassis metal. Could be loose.

    Be careful poking around inside. There's stored voltage inside some components that will give you a nasty tickle if you earth them through your fingers. Use chopstick to tap things, see if anything is loose.

    Any more than that, it's serious. The earliest Nightrains could be old enough to pop poor quality electros.

    Have a look at the power tubes when it's on. See if either of them is redplating. Google 'redplating EL84' so I you know what your looking for
     
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  6. teleblastard6

    teleblastard6 TDPRI Member

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    Dacious, thanks for the help. I got the chopsticks, & I'm gonna do the google
     
  7. Dacious

    Dacious Poster Extraordinaire

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    4996-1305079819-bbd3492b0dce7e55b25a8031385ab294.jpg

    You're looking for something like the tube on the left. If left long enough this will literally cook or melt things, it's often audible as a thrum or deep hum. It's indicative of either bad tube, bad connection, bad resistor.
     
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  8. teleblastard6

    teleblastard6 TDPRI Member

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  9. teleblastard6

    teleblastard6 TDPRI Member

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    I'm gonna follow up on your suggestions, Dacious. I can tell you know about this stuff, & I'm gonna figure it out. Thanks again.
     
  10. teleblastard6

    teleblastard6 TDPRI Member

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    Hello again Dacious. Been checking out Vox NT- Does'nt seem to be redplating after powered up for a while. Noise, [headache inducing hum or thrum] most prominent while in Triode. [7.5 w] Less so in Pentode [15 w]. Noise subsides while on standby. Of course I wanna play in Triode because I'm in an apt. Wish I could determine exact cause so don't get ripped off on a repair. Filter caps still my main suspect.
     
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