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P2P version of Micro Champ

Discussion in 'Shock Brother's DIY Amps' started by scorcht, Jan 17, 2021.

  1. scorcht

    scorcht TDPRI Member Gold Supporter

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    I've been working up a point-to-point version of robrob's Micro Champ, and I'm hoping for some keen eyes to see that the pieces are all connected right. The chassis will go in the top of a cabinet I built around a Weber 12" 12A125A using some ideas from Uncle Doug. In the photo below, the chassis is an L-shaped piece of steel sheet that I cut from an old radio chassis. It slides into the back of the cabinet like a drawer. The bright blue is just painter's tape on which I'm drawing out the pots, switches, etc. The trannies and tubes will hang off the bottom.

    Open drawer.jpg

    Here is the back of the cabinet with the chassis drawer closed and the front of the cabinet.

    Back.jpg

    Front.jpg

    Here is robrob's layout on a circuit board and below is my point-to-point conversion.

    Champ_Micro_Layout_robrob.png

    Champ_Micro_Layout_p2p.png

    The 3/4" borders around the top and sides are off limits - they are where wooden rails are for supporting the chassis. Also I upped the dropping resistor below B+ because the 270DAZ is a bit hotter than the DAX; I may have to fiddle with that.

    Any screw-ups? Any suggestions on the layout?

    Thanks.
     
    gigante, sds1 and robrob like this.
  2. King Fan

    King Fan Poster Extraordinaire Ad Free Member

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    Impressive; well done. I'm not much at proofreading layouts, so I'd just note good safety practice says the household green earth/ground wire shouldn't go to a shared anchor -- it should be mechanically and electrically separate from any other bolts.
     
    Last edited: Jan 17, 2021
  3. scorcht

    scorcht TDPRI Member Gold Supporter

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    Thanks King Fan.
     
  4. D'tar

    D'tar Friend of Leo's

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    If you add the pdf file we can get a better resolution look at your layout. In the tag strips just be cautious that lots of the tabs at mount locations are actual chassis connections. Ymmv. Some are not.

    You may wish to put a lower limitting resistor on the nfb so you can not have 100% signal cancellation when pot is at zero.
     
    robrob likes this.
  5. robrob

    robrob Poster Extraordinaire Ad Free Member

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    It looks good to me. I'd recommend a 250 ohm humdinger so you get 125 ohms per side instead of 50. 100 should work though if you already sourced it.
     
  6. sds1

    sds1 Tele-Afflicted

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    Lazy drive-by to say... rad!
     
  7. scorcht

    scorcht TDPRI Member Gold Supporter

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    @D'tar, thx for the offer of a detailed look. PDF attached (I hope). Also thx for the tip about the NFB resistor. Frankly I'm not sure about the NFB pot - I suspect it's something to twiddle with for a couple o weeks then leave it along. Still, this is a learning project.

    @robrob: thx for the tip about the humdinger pot. Oh dang, now I have to go to the Elliott's again. Heh heh heh. Also big shoutout for your layouts and huge repository of knowledge.
     

    Attached Files:

    robrob likes this.
  8. scorcht

    scorcht TDPRI Member Gold Supporter

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    Thx sds1 (I guess :). I hope it doesn't sound too rad when it's all laced up.
     
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