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First Build - Rob Robinette Micro Champ

Discussion in 'Shock Brother's DIY Amps' started by SJK45, Aug 14, 2020.

  1. andrewRneumann

    andrewRneumann Tele-Holic

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    ha this is fun. I was about to agree with you and then you agreed with me and now I’m disagreeing again. :)

    I think he’s fine using the lower left set of leads (the brown ones labeled 240) for the mains and then connect the gray and purple for his HT+ of 360vac.

    Edit: dang again... what HT+ does this design call for anyway? I forgot we were building a micro.

    Edit edit: Disregard the suggested wiring in this post!
     
    Last edited: Sep 13, 2020
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  2. D'tar

    D'tar Friend of Leo's

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    For safety sake just use the 240v winding. If your secondary voltages are low 50% then we can adjust from there. The wf55 layout had a different PT?
     
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  3. andrewRneumann

    andrewRneumann Tele-Holic

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    Now I think you were right @D'tar. The Primaries are on the right side of the diagram. I just read the ampmaker.com description. I don’t think he needs to jumper the purple and gray though. The secondary HT+ from the 240V secondaries should fall around 320Vdc after rectification and filtering (according to the mfg. website). Rob has 370Vdc labelled on his schematic. 360vac would be way too much voltage after rectification and filtering. So I stand corrected!
     
  4. D'tar

    D'tar Friend of Leo's

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    Well appologies to Sjk45 for adding to the confusion. I have yet to see a PT that has truly 2X primary windings. I have always seen two windings in series to acheive the 240v needs. It will be interesting to see the results here.

    Your secondary connections should be obious for HT. And the heater windings as well. You will need an artificial heater center tap though. And a full wave bridge rectifier discussed earlier in the thread
     
    Last edited: Sep 13, 2020
  5. D'tar

    D'tar Friend of Leo's

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    Leave them long. Cap them individually as you may need them later.
     
  6. SJK45

    SJK45 TDPRI Member

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    43DEC31F-99C4-4E1F-AC52-09077CA32170.jpeg Ok, I think I get it - so blue to where I had previously put the neutral on the switch and then grey either attached to the neutral tab on the power socket or to the wire connected to that tab?.

    The Brown and the purple can be left unconnected but suitably taped up etc. 43DEC31F-99C4-4E1F-AC52-09077CA32170.jpeg
     
  7. D'tar

    D'tar Friend of Leo's

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    Better... shrink wrap etc to protect the flying lead there.
     
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  8. SJK45

    SJK45 TDPRI Member

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    So for the next stage I need to run two further power wires to the diode rectifiers.

    E0D61C67-EF38-4072-97E6-B808FE04B30C.jpeg

    Shall I just use the secondary 240v for that (the two brown wire on the left of the diagram)? (Edited to remove “write”!!)
     
    Last edited: Sep 13, 2020
  9. SJK45

    SJK45 TDPRI Member

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    The lead is long enought to reach the neutral on the socket so I think that I will run it straight there.
     
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  10. D'tar

    D'tar Friend of Leo's

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    These will be your secodary wires to the rectifier

    20200913_153255.jpg
     
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  11. D'tar

    D'tar Friend of Leo's

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    Thats not a great spec sheet!!!
     
  12. SJK45

    SJK45 TDPRI Member

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    No need to apologise thanks so much for helping.
     
  13. SJK45

    SJK45 TDPRI Member

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    Yes those are the ones - I was planning on using those to attach to each end of the diodes?
     
  14. D'tar

    D'tar Friend of Leo's

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    Yes
     
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  15. EmWeAh

    EmWeAh Tele-Meister

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    Cool, that power transformer wiring diagram got phasing dots, huh @King Fan ... ;)
     
  16. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    Looking at the picture of your diode rectifier, post #88.

    The black wire from the diodes to ground is essentially your HT center tap. It should run from the diodes directly to the negative side of the first filter cap for quietest operation.
     
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  17. andrewRneumann

    andrewRneumann Tele-Holic

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    Don’t forget to do this. You might look at the schematic and think “ah those aren’t connected to anything” and leave them dangling. Nope. They will be LIVE when you flip the switch. Get them tidied up and safely insulated from the chassis and themselves.
     
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  18. SJK45

    SJK45 TDPRI Member

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    Thanks this is very helpful. Would you still leave in the earth going from the negative of the V2 Bypass Cap?
     
  19. Lowerleftcoast

    Lowerleftcoast Friend of Leo's

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    For a two star ground scheme, yes. I have built several two star ground amps that are very quiet.
    I have recently decided to use one star ground schemes. To do that the negative of the V2 Bypass Cap would connect to the ground bus nearest the PT. The other side of the ground bus would terminate at or near the input jacks.
     
  20. andrewRneumann

    andrewRneumann Tele-Holic

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    And so your 240v pilot light would be wired to the ends of the blue and gray wires. Did you make a decision on 6.3v vs. 240v bulb?

    Did you end up just going with the American style SPST power switch? Or is that DPST in disguise?
     
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