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In Reply to: RE: update 2 posted by vinnie2 on October 25, 2016 at 07:13:30
"Is there a way to measure what value a swinging choke is at when the psu is powered up?"
Yes, see my posts in the link below.
When you say the ripple dropped, where are you measuring this in the circuit?
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Buy Chinese. Bury freedom.
Follow Ups:
Yes, I attached the dvm probes to last cap. Also, I just got through adding a 7k resistor across each cap to balance the load and help with limiting in rush. Total of 4 caps, 2 groups of 2 in parallel for 87uf in each group. When I checked the ripple this time (same way) it had dropped to 45 mV. Not sure why that happened, but would like to know. Also, I am wondering if I raise or lower the values of the resistors if that will drop the ripple even more. Thanks for the link, will check it out.
Edits: 10/25/16
If the addition of bleeder resistors causes ripple to go down, that might imply the amplifier itself is drawing insufficient current for the chokes to be effective. You can model that in PSUD. 45mV ripple at the output stage probably equates to around 2mV at the speaker. Have you posted a complete schematic of the supply here?
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Buy Chinese. Bury freedom.
If the addition of bleeder resistors causes ripple to go down, that might imply the amplifier itself is drawing insufficient current for the chokes to be effective.
are you referring to AC or DC current?
can you give a scenario where this might happen?
dave
If the inductance of the input choke is less than critical and then we draw more current causing the inductance to be critical the voltage will go down but drawing more current will always make the ripple go up.
Did I get that right?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
but the issue was bleeders causing the ripple to go down. I cannot see anything related to the choke to cause this since increasing current draw always reduces inductance which should make ripple go up.
dave
"but drawing more current will always make the ripple go up."
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
which puts us back to the beginning and me asking why bleeding more current causes less ripple. TK said it could be because the amp may be "drawing insufficient current for the chokes to be effective"
I want to know how drawing current makes a choke more effective.
dave
"I want to know how drawing current makes a choke more effective. "
It doesn't in terms of ripple, it does in terms of voltage regulation.
That is to say, if the inductance is less than critical at the lower current draw and at or beyond critical at the higher current draw.
If the inductance is "on the edge" of being a value that is critical and, with a changing current draw, is falling in and out of critical the voltage regulation will be........bad.
All of that aside, I agree with you. For a given inductance (and cap values) more current draw = more ripple.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Not in it's current form, but I will. I need to do it for my records anyway. I'll try to get to it today. I can hear that the hum is down, so I think I will take a look at it at the speaker again on the scope and see what we get.
I did it in psud, but I did not see anything that indicated a problem like that.
Are they new? What brand and type? They aren't warm are they?
Might be worth throwing a high voltage film cap across the first cap bank...1uF 630 volt should do but the bigger the better.
Could be your caps just aren't up to snuff.
nt
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