who can tell me about 5U4Gs?

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by GuitarTek86, Jan 28, 2006.


  1. GuitarTek86

    GuitarTek86 Member

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    Rectifier tubes. what I wanna know is do they need to be replaced as often as poweramp tubes and preamp tubes?
     
  2. Richard Guy

    Richard Guy Member

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    Generally speaking,....no
     
  3. robbieboyette

    robbieboyette Member

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    Back when I had a Duncan Convertible amp in the mid to late 80's it used a 5u4gb and I changed it a couple of times..and then I went to a solid state "plug" that fit right into the tube socket. Amazingly it sounded just great. A tech told me at the time that since it was a rectifier tube it would be just fine to do it with a solid state plug. Of course now that I HAVE to have a tube in every damn signal path....LOL!...I would tell that guy he was crazy. But back then it seemed to work just fine. Go figure...
     
  4. GuitarTek86

    GuitarTek86 Member

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    good to know. mine is both tube and silicone dioxide diode (switchable) it's a Mesa Stiletto Trident. versatile as heck..... so nice
     
  5. donnyjaguar

    donnyjaguar Member

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    I wouldn't recommend replacing a vacuum tube rectifier with silicon diodes on an amplifier that doesn't have a Standby/Run switch. The B+ voltage will come up long before the cathodes are properly heated and in so doing will create hot spots that wear the tubes out prematurely.
     
  6. Blue Strat

    Blue Strat Member

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    NOS rectifiers seem to last 20+ years. New production rectifiers seem to last a year or less.
     
  7. Kiwi

    Kiwi Silver Supporting Member

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    How do you tell when your rectifier tube needs replacing? What signs to look or listen for?

    = K
     
  8. johnny q

    johnny q Member

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    So the Russian rectifier tubes that came stock in my 1999 Mesa Dual Rectifier............couldnt hurt to replace them 6 years later????? :)

    JQ
     
  9. trdlasvegas

    trdlasvegas Member

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    Mike,
    I certainly understand and appreciate that you sell NOS tubes but that is a unfair and untrue statment. Just look at the post above for example, he's had them for 6+ years!

    While it is hard to put a time on how long they will last, New Production Rectifier tubes generally last YEARS not MONTHS as you are implying.

    -Tony
     
  10. johnny q

    johnny q Member

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    This is actually an honest question - not a wise crack! :jo

    I know what to look for when diagnosing failing Pre and Power tubes......no idea what to listen for in failing rectifier tubes. Mine may be bad and I dont even know it....

    JQ
     
  11. fabiomayo

    fabiomayo Member

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    Me too. And I'd really like to know if anyone can help...
     
  12. Blue Strat

    Blue Strat Member

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    Maybe 5U4s are different, but I hear about new production 5AR4s all the time which last less than a year. In almost everything, you generally get what you pay for.
     
  13. Blue Strat

    Blue Strat Member

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    Statistically (and realistically), one case in 1000s isn't very significant. There are exceptions to everything. I know for a fact that new production 5AR4s rarely last a year of moderate to heavy use.
     
  14. Blue Strat

    Blue Strat Member

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    It's rare to see a rectifier in the "in between" state. I've worked on 100s of amps, tested 10s of thousands of tubes. Rectifiers typically work or they don't. They often take out your main fuse when they go. I can remember only 2 cases in which rectifiers were in a transitional state. They were producing much lower DC voltage than normal, and the amps sounded anemic and broke up way early.



    Unfortunately, there are rarely warning signals. The heater of a tube is a lot like a lightbulb, it works or not and it usually "goes" when you apply power. The more on and off cycles it sees, the more likley it is to go on the next power up.

    The best defense is to have a backup.
     
  15. fullerplast

    fullerplast Senior Member

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    So put into the more usual "hours of use", you are saying that new production 5AR4's have roughly 500 hours of useful life? (That would be an average of 10 hours a week, and would also give the NOS tubes rated for 10,000 hours a 20 year life.)

    That seems low to me, but I certainly haven't seen as many new production failures as you see, being in the business.
     
  16. Blue Strat

    Blue Strat Member

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    Read the boards, take to amp builders, etc. New production 5AR4s rarely last a year. The Chinese ones often don't survive the first power cylce.

    Wouldn't it suck to have your amp die in the middle of a gig for the sake of saving $20 on a 5U4 rectifier?:rolleyes:
     
  17. Blue Strat

    Blue Strat Member

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    Read the boards, talk to amp builders, etc. New production 5AR4s rarely last a year except under VERY light use. The Chinese ones often don't survive the first power cylce.

    Wouldn't it suck to have your amp die in the middle of a gig for the sake of saving $20 on a 5U4 rectifier?:rolleyes:
     
  18. fullerplast

    fullerplast Senior Member

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    You're preaching to the choir here Mike...I use NOS rectifiers. ;)

    I'm not disputing your findings, I'm just genuinely surprised that the life of new production rectifiers is only 500 hours. There are some reputable builders that do use them. Any idea what is failing on them? Just shorting?
     
  19. Blue Strat

    Blue Strat Member

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    Reputable builders use new production power tubes also. Most of them last only 500 hours as well. What do you expect for $15 a pop? It's reality.

    The rectos seem to short and take out fuses when they die.
     
  20. jbird

    jbird Member

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    JQ, I've had my '00 Dual Rec since new! Replaced the Rectifiers once, and not because they were bad!
     

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