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Old 12th July 2013, 07:03 PM   #1
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Default LME49810 Problems

Hello,
I bought a finished module with lme49810. The rectangle behavior is not optimal. In Figure 1 corresponds to 1 cm 1 volt, frequency is 1000 Hz Figure 2 is 1cm 2 volts. The connected load is 8 ohms.
The amplitude of a sinus signal increse between 2 kHz and 20 kHz. An increase in the Compensating capacitor does nothing. Does anyone have an idea what I can try to do?

Best regards Gerd
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Old 12th July 2013, 09:13 PM   #2
nattawa is offline nattawa  Canada
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I could be wrong but it appears to me like the probes compensation is way off.
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Old 13th July 2013, 07:09 AM   #3
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Thank you, ist an old Oszilloskop. I will check the Oszilloskop. I have a idea, the curves look like the discharge of a capacitor. I'll check the dc servo
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Old 13th July 2013, 07:53 AM   #4
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IF your oscilloscope is not the problem......
check that the value of the 1M resistor on the DC servo +ve input pin 3 is actually 1M .
Have you connected anything to the FB point on the connector that might be causing the problem.
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Old 13th July 2013, 08:05 AM   #5
AndrewT is offline AndrewT  Scotland
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Check the input signal. Your generator may require a 50r load to generate the correct squarewave shape.
If possible, display both input and output signals to allow comparison and to see how/what has changed on passing through the amplifier.
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Last edited by AndrewT; 13th July 2013 at 08:10 AM.
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Old 13th July 2013, 08:26 AM   #6
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Quote:
Originally Posted by nattawa View Post
I could be wrong but it appears to me like the probes compensation is way off.
My first thought entirely. I would check the input waveform as well for comparison.
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Old 13th July 2013, 12:09 PM   #7
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The oscilloscope is ok, it is a Hameg 20Mhz 2 spots from 1990. I have checked it with the Component Tester. But the Wobbelfunktionsgenerator is not ok. I would never have believed it. But as soon as I connect the generator to the amplifier input, the shape of the rectangle changed. The amplitude of a sine-shaped signal changes depending on frequency. I will install a fast buffer in the frequency generator. Thank you for your help. It would never come of itself. I always think too complicated.

Gerd
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Old 14th July 2013, 07:12 PM   #8
AndrewT is offline AndrewT  Scotland
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compare signals.
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