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Old 19th April 2011, 08:05 PM   #1
ehous is offline ehous  United States
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Default Help with Op Amp outamp

I am experimenting with a op amp in a existing pre amp circuit. The wave is pointed at the bottom and flat on top. I have a working circuit and tested it, it works fine. I also tested an op amp out of the circuit and it was the same pointed an flat. I have a 2 channel scope and the the input circuit is good. All of this leads me to believe my test power supply is the problem. Obviously, I am not experienced and any help will be appreciated.
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Old 19th April 2011, 09:07 PM   #2
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Working with Cranky Op-Amps
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Old 19th April 2011, 09:13 PM   #3
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Quote:
Originally Posted by ehous View Post
I am experimenting with a op amp in a existing pre amp circuit. The wave is pointed at the bottom and flat on top. I have a working circuit and tested it, it works fine. I also tested an op amp out of the circuit and it was the same pointed an flat. I have a 2 channel scope and the the input circuit is good. All of this leads me to believe my test power supply is the problem. Obviously, I am not experienced and any help will be appreciated.
Are you using a dual supply, like + and - voltage? Is the input signal coupled to the opamp through a capacitor or directly?
Can you scribble a circuit diagram of your amp?

jan didden
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Old 19th April 2011, 09:19 PM   #4
ehous is offline ehous  United States
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+15vdc / -15vdc, 470uf caps on the input legs of the op amp. Note: very confusing circuit for servo amp input. thanks again.
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File Type: pdf Schematic Design_ Acoustat Input 4.prj.pdf (14.5 KB, 30 views)
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Old 19th April 2011, 09:34 PM   #5
ehous is offline ehous  United States
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Ignor previous circuit, the attached is the one actually in use.
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File Type: pdf Schematic Design_ Acoustat Input 4.prj.pdf (27.1 KB, 31 views)
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Old 24th April 2011, 04:07 PM   #6
ehous is offline ehous  United States
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I was informed that by finding dc in the output meant there was a break in the feed back circuit. after tracing it back, a missing jumper was noted. With jumper installed, dc is at zero & the wave was smooth.
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