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kbmcnich
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Hello all, I'm new to this forum. I have a scenario that I don't quite understand with my oscilloscope, a tektronix 2246. I'm using it to see the waveform of a square wave frequency generator circuit. The circuit basically has two stages: The first is a 555 timer astable oscillator circuit that is used to generate a square wave from approximately +7V to ground. It is powered by a regular 9V battery. This output then goes into an inverting amplifier circuit, using an LM675 op-amp to output a wave from approximately -23V to ground. This circuit uses a dual power supply; the +9V from the 9V battery and a regulated 24V DC power supply, hooked up "backwards" to get -24V for the -VEE pin of the op-amp. When leave the -24V supply disconnected, and attach the probe common to my circuit ground, and the probe itself to my 555 output, I get a beautiful square wave at the exact frequency and voltages it should be. When I connect the -24V supply, and attach the probe common to my circuit ground, sparks fly. Literally. A huge spark emits from the connection point, so I instinctively pull the clip away from the point of contact. Does anyone have any idea what could be going on here? Using a much higher capacitor value to slow the wave down and read it with a multimeter, I find that the wave is in fact going from about 0.6V to -23.4V, so the wave is working properly, I just would really like to see it on the scope. Any help or suggestions would be much appreciated.
Thanks
Thanks