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C-R-C or C-R-C-R ? (Read 3921 times)
Corey
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C-R-C or C-R-C-R ?
10/10/16 at 02:18:40
 
Hey guys.

I have decided to build my own ZBox and am designing the power supply.

So far I have come up with the capacitors which are going to be Solen Fastcaps (47uF and 220uF)

I want to get 100 VDC instead of 95 VDC that Steve uses.

Steve used a 33K resistor in the standard supply in a C-R-C configuration.

Is it better to use only a resistor between the caps or can I add an extra resistor after the second cap in a C-R-C-R ?

Here is the C-R-C configuration :

https://web.archive.org/web/20081227012251/http://www.decware.com/newsite/zkit5....

Corey  :)
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Core32
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Re: C-R-C or C-R-C-R ?
Reply #1 - 10/10/16 at 13:13:21
 
What would be the purpose of the second resistor?

Also, note that on Steve's schematic the note: "Voltages shown under load".
This is telling you that the voltage will not be exactly 95V (100V) but will vary based on the load the second cap sees. This will not be a perfectly stable value and will be a little different tube-to-tube. It will also NOT be close to what you expect if you fire it up without the tube load.
So you can tweak it up by lowering the 33K resistor value a bit but I would not be too worried about getting exactly 100V under all conditions.

Lastly, the voltages these circuits deliver are very dangerous so please be careful when working with them and note that the large value capacitors can hold a high voltage charge for a long time after input power is removed, especially if the load (tube) has been removed.
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Corey
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Re: C-R-C or C-R-C-R ?
Reply #2 - 10/10/16 at 22:11:40
 
"What would be the purpose of the second resistor?"


My thinking was how the speed of the supply would change if I split of the resitors. Let me hypothetically explain :

Scenario A) Just like Steve did; a 33K resistor bwtween the 2 caps to net 95VDC.

Scenario B) An 18K resistor between the caps then another 15K resistor after the second cap. Wouldn't this effectively split up the resistance application and increase the discharge speed of each capacitor? Thereby increasing the speed of the supply?

Corey  :)
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Core32
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Re: C-R-C or C-R-C-R ?
Reply #3 - 10/20/16 at 15:28:17
 
Sorry, I didn't get an email showing you had replied.  :(

I don't think so. Without doing any detailed analysis I think you would just get more ugly ripple at the output of the second resistor based on the varying current requirements of the load.
Capacitors are inherently good at holding a voltage steady. Adding the resistor post cap will reduce that.
Hopefully my DC analysis memory is still ok.   Smiley
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Corey
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Re: C-R-C or C-R-C-R ?
Reply #4 - 10/20/16 at 15:56:20
 
Thanks very much!   Smiley
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Crazy Bill the Eel Killer
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Tubes Rule !!

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Re: C-R-C or C-R-C-R ?
Reply #5 - 04/24/17 at 01:42:30
 
Hello Corey,
Core 32 is spot on. However,
add another cap after that 15K resistor to effectively add another filter section.

You will have a very quiet supply. Much more so than just the single RC section in the original supply.

Cheers,                  Crazy Bil
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