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Thread: 5u4 rattles on powerup

  1. #1
    Join Date
    May 2008

    5u4 rattles on powerup

    Hello all. I am new to amp building and have been able to avoid major failure for 3 builds now. I have noticed in my 5E7 that the JJ 5U4 starts to rattle when the mains are applied (325-0-325). This is not reproduced in the audio circuitry to any effect, but it keeps rattling as long as it's on. It does not matter if the standby is on or off. The B+ is ~ 410 (pretty close to spec.) I would like to know:
    - Is this normal?
    - Does anyone used anode resistors on a rectifier tube and would this help?
    The amp sounds pretty good, but there is always room for improvement.

  2. #2
    Supporting Member tubeswell's Avatar
    Join Date
    Feb 2007
    Wellington NZ
    Try a different 5U4G in there. It is not usual for a rectifier to rattle
    Building a better world (one tube amp at a time)

    "I have never had to invoke a formula to fight oscillation in a guitar amp."- Enzo

  3. #3
    Join Date
    May 2008
    Darn. Thats the second straight JJ 5U4 that's defective then. The last one was chalky with a hairline crack near the base. Back to the copper cap...

  4. #4
    Senior Member booj's Avatar
    Join Date
    Jun 2008
    You may want to check the health of your first power supply cap. If its leakey it could cause excessive loading and the rattling you are talking about

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