want to use the Hammond 290CAX rather than 40-18027

Discussion in 'Shock Brother's DIY Amps' started by ouaouaron, Oct 11, 2019.

  1. ouaouaron

    ouaouaron TDPRI Member

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    starting my planning for the champ micro and found that with shipping the Hammond is about $30 cheaper and Rob says it works well.

    I know how to use the wires in the ClassicTone (red, red, red/yellow, green, green, green/yellow and black, black).

    Does anyone know how to use the correct wires in the Hammond?

    Need to know which are the HT, HT center tap, 6.3v and 6.3v center tap, and which is for the power and power cord (likely black).
     
  2. rghill

    rghill Tele-Afflicted Silver Supporter

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  3. Paul-T

    Paul-T Tele-Meister

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    I might be wiring mine into my Champ this weekend. Only difference is I'll be wiring my primary in series where you will be doing it in parallel. I see from a previous post you would wire orange and white together, as neutral, with brown and black as hot/live.
     
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  4. rghill

    rghill Tele-Afflicted Silver Supporter

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    According to the diagram, there is no physical CT for 6.3V leads, so you will need a virtual center tap.
     
  5. ouaouaron

    ouaouaron TDPRI Member

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    thanks for the help, I am leaning toward the ClassicTone now. I can read and understand some of the Hammond diagram but with my level of knowledge the ClassicTone is easier.
     
  6. zook

    zook Friend of Leo's

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    I have used this transformer and really think it is the best choice for Champs and Princetons. Use the 315 Volt taps and cut the 275 volt taps short. Put some heat shrink over the ends leaving about 3/8" to fold back onto itself.

    Be sure to wire it for the appropriate primary voltage
    upload_2019-10-12_21-0-27.png
     

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    Last edited: Oct 13, 2019
  7. Wally

    Wally Telefied Ad Free Member

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    What is your target B+?
     
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  8. dan40

    dan40 Tele-Afflicted

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    Wally...Rob shows the B+ at 400vdc (275-0-275) at the first node for the Micro Champ.

    I recently built the Micro JCM800 circuit from his website and it is a rockin little amp! Finally able to crank a tube amp in the house and not upset the wifey. Good luck with your build!
     
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  9. King Fan

    King Fan Friend of Leo's

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    Yeah, this is a Micro -- the advice above to use the 315 taps doesn't line up with Rob's design.
     
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  10. Wally

    Wally Telefied Ad Free Member

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    Well, I haven’t studied that Micro; but something told me that one might want to look at the 275-0-275 winding. I decided to ask instead of opining as normal for me...some look for something with higher voltages. House amp...single 6V6...
     
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  11. King Fan

    King Fan Friend of Leo's

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    Heh, Wally, good one. In this case, micro means single 12AU7 or 12BH7 power tube. Rob suggests 275 HT for this (he uses SS rectification), but also says:

    "Really any 190-0-190V (285V B+1) to 300-0-300V (430V B+1) transformer will work. If you plan to use a tube rectifier like the EZ81 (9 pin) or 5Y3 (8 pin) then I recommend the CT 40-18028 300-0-300v.... The higher voltage is needed due to the 30+ volt drop of a tube rectifier."​
     
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