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    weird noise need help

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    Jong5664

    Posts : 3
    Join date : 2015-01-28

    weird noise need help

    Post by Jong5664 on Wed Jan 28, 2015 6:18 pm

    Mad Last week, I just got my first Dynaco..DYNA ST70, factory wired, PAS 3 and FM1. Everytime I turned ON the amp im hearing a weird noise coming out from left speaker and will go away for a few seconds. Im not sure what causing the weird noise. Need help just new to this.

    tubes4hifi
    Admin

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    Join date : 2008-11-30

    Re: weird noise need help

    Post by tubes4hifi on Wed Jan 28, 2015 6:29 pm

    weird noise - could be anything . . .
    try swapping the left side tubes with the right side tubes, and see if the "weird noise" follows the tubes.
    If you're lucky, it does, and you have a bad tube. If not, the weird noise is being caused by something other than the tubes.
    Could be a bad resistor, bad capacitor, bad solder joint, bad ground . . .

    j beede

    Posts : 317
    Join date : 2011-02-07
    Location : California

    Re: weird noise need help

    Post by j beede on Wed Jan 28, 2015 8:13 pm

    "Goes away for a few seconds" (meaning the weird noise comes back again) or "goes away after a few seconds" (and doesn't come back)?

    Jong5664

    Posts : 3
    Join date : 2015-01-28

    Re: weird noise need help

    Post by Jong5664 on Wed Jan 28, 2015 9:06 pm

    Goes away after a few sec and doesn't cone back

    MontanaWay

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    Age : 58
    Location : Cameron, Montana

    Re: weird noise need help

    Post by MontanaWay on Wed Jan 28, 2015 10:52 pm

    sounds like as B+, your high voltage supply, comes up, something struggles with it for a few seconds until it settles down.
    As tube4hifi suggested though, swap over tubes and see if it follows from one channel to the other.
    Hopefully it is a tube, if not, yes, could be anything right now.
    After you've used the amp for a while, turning it off, then turning it back on again after a short wait period, i.e.., whilst the amp is 'hot', does the same noise appear, or does it only happen when the amp is 'cold'

    Jong5664

    Posts : 3
    Join date : 2015-01-28

    Re: weird noise need help

    Post by Jong5664 on Thu Jan 29, 2015 12:06 am

    Noise occurred only when amp is cold.

    MontanaWay

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    Age : 58
    Location : Cameron, Montana

    Re: weird noise need help

    Post by MontanaWay on Thu Jan 29, 2015 10:46 am

    Jong5664 wrote:Noise occurred only when amp is cold.

    I would point my finger at a tube to begin with, and swap the power and driver tubes from one side to the other.
    If you're not familiar with BIASing power tubes, make a note of each tubes position, then start swapping them from side to side, one at a time, and see if that noise will follow, this is the quickest and easiest step. Once done with this step, return the power tubes to their respective/marked positions.
    If the noise stays, then we'll have to dig deeper, possibly a bad solder joint (more likely) or 'dying' component/s.

    wildiowa

    Posts : 120
    Join date : 2012-03-19

    Re: weird noise need help

    Post by wildiowa on Thu Jan 29, 2015 11:01 am

    Hmmm..it goes away, and does not come back. What was that about letting sleeping dawgs lie? In my case, and with my luck, digging into it would certainly bring more problems than are solved. All I know from my experience and especially from various posts here the Dynas seem to be particularly sensitive to ground issues and solid solder connections.

    MontanaWay

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    Re: weird noise need help

    Post by MontanaWay on Thu Jan 29, 2015 11:17 am

    wildiowa wrote:Hmmm..it goes away, and does not come back. What was that about letting sleeping dawgs lie? In my case, and with my luck, digging into it would certainly bring more problems than are solved. All I know from my experience and especially from various posts here the Dynas seem to be particularly sensitive to ground issues and solid solder connections.

    Not just Dynas, but especially where high voltages are present, ie tube amps in general. What is unique with Dynaco gear is that most were user built, and it is easy enough to make a bad solder joint.

    wildiowa

    Posts : 120
    Join date : 2012-03-19

    Re: weird noise need help

    Post by wildiowa on Thu Jan 29, 2015 11:30 am

    The grounds are also so weird. You would think that everything grounded like the input and output jacks etc. would be OK going to the chassis but noooooo....I made this mistake when adding some phone jacks for PA speakers (heresy among purists, I know..) but when you ground stuff where it should not be you got troubles.

    MontanaWay

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    Join date : 2014-02-06
    Age : 58
    Location : Cameron, Montana

    Re: weird noise need help

    Post by MontanaWay on Thu Jan 29, 2015 11:34 am

    wildiowa wrote:The grounds are also so weird. You would think that everything grounded like the input and output jacks etc. would be OK going to the chassis but noooooo....I made this mistake when adding some phone jacks for PA speakers (heresy among purists, I know..) but when you ground stuff where it should not be you got troubles.

    Aka ground loops :-)

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