First Build - Rob Robinette Micro Champ

andrewRneumann

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Ok, I edited my post to reflect what you are saying. If your voltages are 50% of expected then you will need to adjust

Edit my edit. Lol

Youneed to connect the grey and purple together for 240
View attachment 763914

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!
 
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D'tar

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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?
 

andrewRneumann

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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?

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!
 

D'tar

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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
 
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D'tar

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If I connect the blue 240v to where I put the neutral and then attach the neutral to the grey wire where do the other two (purple and brown) come in?

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

SJK45

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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
 

SJK45

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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”!!)
 
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SJK45

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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

No need to apologise thanks so much for helping.
 

Lowerleftcoast

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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.
 

andrewRneumann

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



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.
 

SJK45

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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.


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

Lowerleftcoast

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Would you still leave in the earth going from the negative of the V2 Bypass Cap?
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.
 




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