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Beaufays
Joined: Dec 14, 2018 Posts: 4 Location: Belgium
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Fri Dec 28, 2018 10:02 am Post subject:
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It looks like the positive portion of the signal is being clipped just above zero volts. Measure Vss and Vdd at the opamp power pins. It's possible that a bad connection prevents the full positive voltage from entering the opamp. I'm assuming that this circuit is driving nothing. If it's driving some circuit, disconnect the load and measure the waveform again.
I can't say that it won't or doesn't or can't happen, but a bad opamp is probably not the problem. If you have known good opamps, try one of those to be sure.
I won't buy electronic parts from e-bay. But then I always avoid e-bay because I just don't trust it. It is possible to get cheated, but your milage may vary. _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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Beaufays
Joined: Dec 14, 2018 Posts: 4 Location: Belgium
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Posted: Fri Dec 28, 2018 10:07 am Post subject:
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Hey, yeah the circuit is not driving anything, but that doesn't seem to affect it anyway..
will measure power input, and buy some chips at the local shop to compare.
thx |
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Grumble
Joined: Nov 23, 2015 Posts: 1294 Location: Netherlands
Audio files: 30
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Posted: Fri Dec 28, 2018 4:21 pm Post subject:
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Quote: | It looks like the positive portion of the signal is being clipped just above zero volts. |
That’s hard to tell because the scope is set at ac, so the voltage could be positive, negative or around 0volt. _________________ my synth |
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JovianPyx
Joined: Nov 20, 2007 Posts: 1988 Location: West Red Spot, Jupiter
Audio files: 224
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Posted: Fri Dec 28, 2018 4:35 pm Post subject:
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I agree that there's no way to guarantee that the OP set zero on the scope properly, however it is standard practice for some of us. There is most definitely clipping going on there. One of the simplest ways to account for clipping in this extremely simple circuit is for a supply line to be severely degraded with resistance or disconnect. It was only this intuition that caused me to suggest what I did. And I did not rule out a bad opamp, a blown output driver transistor could cause this as well. _________________ FPGA, dsPIC and Fatman Synth Stuff
Time flies like a banana. Fruit flies when you're having fun. BTW, Do these genes make my ass look fat? corruptio optimi pessima
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Beaufays
Joined: Dec 14, 2018 Posts: 4 Location: Belgium
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Posted: Sat Dec 29, 2018 10:12 am Post subject:
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hey,
think I found the problem. setting the scope to DC showed me the OSC was oscilating at around 12V... hence the clipping...
thanks for helping look in the right direction! |
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