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My klon VB rail is wonky

Started by disorder, May 08, 2017, 10:32:28 PM

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disorder

My klon seems to sound alright but I'm getting a strange voltage reading on one of the TL072, the other one seems ok. I am using the TC1044SCPA charge pump. On IC1 pin 3 I'm getting a voltage reading that starts at about +3.54VDC and slowly goes down the longer I keep my meter on it. The other side of R2 reads +4.5VDC as expected. Is this normal or should I swap out IC1? IC2 pins 3 and 5 are directly connected to VB rail and both have the expected +4.5VDC.

And on an unrelated note, my +18V line is only reading +16.7VDC... again, is this normal?

Schematic I used : http://imgur.com/DwJq9Gg

disorder

Looking at other forum members who posted their voltages it seems this is normal. Not sure why this pin wouldn't be held at VB via R2 though...  :o

nzCdog

Your Voltmeter acts like a big resistor to ground while it connected and you're taking measurements.  It will be slowly discharging the Cap C18, which may explain what you're seeing.

Regarding the 18v line, it will depend on your supply Voltage, the forward voltage drop of your diodes, how leaky your caps C20-21 are... etc.  Its probably OK.

I haven't built the circuit, so can't comment on the expected voltages.  Is there a problem with the sound of the pedal?  If not I'd say leave well alone, there is always a degree of tolerance for these circuits :)

gtr2

I don't know what particular klon project you're referring to but check cap polarity if you're using any polarized coupling caps on the input of the opamp.  It can create the issue you describe if you have the polarity reversed.

Josh
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