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In Reply to: RE: Negative bias supply problems posted by Paul Joppa on June 25, 2017 at 17:57:06
Here is the schematic. The IT is not in a circuit, the amp I want to use it in has yet to be assembled.
It looks like you're minimum voltage occurs when the 25k pot is effectively shorted. I would rather not vary the current draw on the negative rail depending on its output setting. Also, 15k and 47k looks to have a minimum output slightly more negative than 40V...so I am not quite sure how you get this pup down to 32V. It could be that the 15k/10 uF RC is knocking down a lot of ripple, and that there exists plenty of it at the 47 uF doubler stack.
I tend to want more capacitance than you have shown...like 10x, and at a minimum 5x...:)
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I get the voltage I wanted and in the desired flavor. I appreciate what you are saying about filter capacitance but is not ripple that is at most a fraction of the DC current when that current is only one ma not something to worry about?
Wonder why "R?" Maybe, check the resistance. I don't think you need this. Just compensate by adjusting R1 and R2 values, downstream.
You sure the polarity of the diodes and 'lytics are correct, in the circuit? Must be (+) to ground.
R? worked out to be around 9K. The transformer is a Hammond that is identical in all respects to the Allied part. I used UF diodes, C3 is 100 uf because that was what I had, and the pot is 20K. It does seem to take a long time for the voltage to come up to my desired -32 volts, might this have anything to do with the value of C3?
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