Mission amps 5E3 deluxe weirdness!

Discussion in 'Amps/Cabs Tech Corner: Amplifier, Cab & Speakers' started by Clear Guy, Apr 12, 2008.

  1. Clear Guy

    Clear Guy Member

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    The amp in discussion is a Mission amps Tweed Deluxe kit that I built. It has slightly bigger transformers and beefed up bias supply so it can take 6L6's with with a 5U4.
    I am running 6V6's with the 5U4 currently.

    Problem:
    When I am in full play mode the amp will just fade out to no sound all of a sudden as if I flipped the standby on but the light is still lit and in play mode. The quick fix is to shake the amp and hit it on the side a bit and then the sound starts to slowly fade back up to full volume. It will stay off quite a while until mess with it. Its sounds perfectly normal when running but just fades out arbitrarily. When it comes back on it will sometimes stay on for a hours. It all started last night after a 4 hour rehearsal. I messed with it all day today trying various things.

    Maybe getting to hot? I dont get it. Odd!

    Anyone have any bright ideas?
     
  2. VikingAmps

    VikingAmps Member

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    Most likely a bad connection somewhere.
     
  3. Nolatone Ampworks

    Nolatone Ampworks Silver Supporting Member

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    +1 on that.

    One thing I suspect a lot of folks neglect to realize when they build these kit amps is than, when soldering, if heating up an eyelet and dropping a lead into the melted solder, that's not always enough: Make sure the new lead is hot enough to flow with the solder. I reheat the eyelet with the new lead in place and flow some new solder in.
     
  4. Dave C

    Dave C Gold Supporting Member

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    I agree with the bad connection...and I would start looking at filament connections since you mentioned the volume ramps back up slowly.....like a tube heating back up perhaps.
     
  5. Groovey Records

    Groovey Records Member

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    don't wack that puppy any more you can make it worse.

    solder joint expanding when The amp gets hot ?

    everyone here seems to agree?
     
  6. Clear Guy

    Clear Guy Member

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    Thanks everyone for your time. I will look it all over and keep monitoring it. This could be a tough one to figure out. The top of the chassis gets almost too hot to touch for longer than 4 seconds. It might have something to do with the heat.
     
  7. DGDGBD

    DGDGBD Member

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    Cold solder joint/bad ground on the power tube cathode resistor?
     
  8. Clear Guy

    Clear Guy Member

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    I figured it out using you all's helpful advice. It turns out it was one of the two wires going to pin 7 (filament wires) on the power tube that was just sitting in the eyelet but not soldered to anything. All fixed and sounding great. Thanks again Guys.
     

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