Champ Micro build thread

Discussion in 'Shock Brother's DIY Amps' started by dotbot, Jan 18, 2019.

  1. dotbot

    dotbot TDPRI Member

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    I've really enjoyed playing the Champ Micro for the last several weeks. It's a sweet practice amp. But I'd been bummed that I was getting a fairly strong hum when powered up, even without any input.

    I saw on this thread that a solution to the problem is to add an additional filter cap and that @robrob has changed the schematic for the Deluxe Micro accordingly.

    So I bought a JJ 50+50 uF at 500V can capacitor. This morning I disconnected the original 47 uF. You can see it sticking up in the photo but it is completely out of the circuit, and I clipped in the new 50+50. I followed the Deluxe Micro schematic for this since it is very similar, at this point, to the Champ.

    [​IMG]

    The good news is that it works! I'm happy to say that the hum is hugely reduced. I wouldn't say it's "dead quiet" but it is nothing to worry about anymore.

    The resistor between what is now B and B+1 was measured to be 462 ohms.

    New voltages:

    B: 395V
    B+1: 386V (used to be 399V)
    B+2: 275V (used to be 279V)

    Now I just have to figure out where I'm going to mount the can cap, solder up the connections, and put it all back together. :D
     
    jtcnj and sds1 like this.
  2. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Yea, I need to update the Champ Micro schematic and layout to add the extra filter stage . . . and done.
     
    Last edited: May 29, 2019
  3. Paul-T

    Paul-T Tele-Meister

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    thanks for the reminders, guys, as I have a basket all ordered at tube-town, just waiting for a late payment I'm owed before I press the button, and I see i'm one filter cap down.

    @robrob , thanks for all your amazing work. If poss, you need to update the Deluxe Micro Bill of Materials from 1 x 47uF to two, for any people not paying full attention (like me).
     
  4. robrob

    robrob Poster Extraordinaire Ad Free Member

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    Sorry about that Paul-T, I'll update it.
     
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  5. Meteorman

    Meteorman Tele-Holic

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    you da man, Rob... don't forget that 470/2w voltage dropper between 'em.;)
    I'm ordering parts for a Micro Deluxe build right now.
    went with the Hammond 290CAX and 1750A.
    Plus SS rectifier.
    Think I can get a head unit put together under $250 all in.
    I'll post pics once things get rolling.
     
    robrob and Paul-T like this.
  6. Paul-T

    Paul-T Tele-Meister

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    thanks for the 470 ohm reminder, I missed that too.

    Toroidal PT for me, trying to keep my costs well down. Just need to find someone who'll swap their 8 inch Jensen for my 10 inch Jensen and I'm home.
     
    robrob likes this.
  7. ouaouaron

    ouaouaron TDPRI Member

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    I really like your homemade chassis (oriented toward the back not up like Fender and like the wood cab.
     
  8. ouaouaron

    ouaouaron TDPRI Member

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    what is the length and the height of the chassis? 10" by 2"?
     
  9. dotbot

    dotbot TDPRI Member

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    Sorry I didn't see this question!

    The chassis is 12" wide by 2" high by 5" deep.
     
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