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Forgetting to connect amp to speakers.

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Strikerfox, Feb 15, 2009.

  1. Strikerfox

    Strikerfox Member

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    Jun 22, 2008
    Alright guys, i know one of the ground rules of using a tube amp is to have it connected to a load before turning it on. I stupidly forgot that i had connected my other head to the cab i was going to use. So basically, my AC30h was without a load when i turned it on. now here is where my question begins. I left my amp on standby for atleast an hour, thinking i was going to play it, but instead something came up and turned off the amp once i came back. Worst of all, this happened two days in a row. when i went to play it i realized it was not connected to the speakers and freaked out. Regardless, i connect the load and begin to play it, and it sounds alright. i cant 100% put my finger on it if it sounds somewhat off from before i did this stupid thing, but the one difference is that there is a crackle when you turn the master volume from 0 to about 1.5 in the dial. then its fine. Never did that before. also a slight volume spike when going from 0 to 1.5, again never did that before.

    Let me know your thoughts on this, (ASIDE from calling me a DUMBASS), experiences, or what not. Do you think the tubes would have taken the hit or the transformer takes most of the hit when this happens. Since it was only on standby, could that mean less harm was done????. Thanks guys.
     
  2. Structo

    Structo Member

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    Oregon
    If the amp was on standby the output transformer is not getting high voltage.
    It's when you flip off the standby and have power going to the OT that is going to cause problems.

    Some OT's are more robust than others, thicker insulation, etc.

    Scratchy pots can be cause by dirty or pitted carbon traces inside or from a leaky coupling cap that is putting DC voltage on the pot.

    What happens to the OT when you don' have a load on it is the voltage can arc or burn through windings on the primary side and short it out completely or damage it enough that you hear something is wrong.
    My advice is to take it to a reputable tech and have him check it out.
     
  3. Strikerfox

    Strikerfox Member

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    Jun 22, 2008
    Thanks a lot guys, you can always count on the people on this forum for help.
    So far the amp is still going strong, if i see any issues ill take it into the shop. kinda broke though since i just bought a zendrive and a 2nd blues devil
     
  4. ntasher

    ntasher Member

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    Jan 18, 2009
    You can relax - nothing happened. To fry the OT and power tubes you need to PLAY the amp at MODERATE TO HIGH VOLUME. Leaving it in standby, as you were told, really does not provide any power to the electronics (other than heating the filaments) so no issue there. Leaving it ON and not playing introduces constant current through the OT primary which results in no current at the secondary (that is connected to the speaker) so the OT and the tubes really do not "see" the speaker to tell if it is connected or not. Only when you start to play with no load connected the OT and tubes will see extreme voltages that may result in damage. That said, modern tube amps have protection diodes installed to the OT to prevent such arching so you are probably more than OK.
    The interesting part here is that once you suspect a problem - you start hearing other stuff that was always there and you never paid attention to.. how strange is that?
     
  5. cugel

    cugel Member

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    i have done this to all my amps i think and have been lucky to not have had a problem
     
  6. Strikerfox

    Strikerfox Member

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    Jun 22, 2008
    haha that is very true. its as if you forget the sweet tones you can get and being to hear the nuisances because of paranoia lol.
     

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