Question: Let me begin with the disclaimer: I am a mathematician and not an electrical engineer. That being said, surely I am missing something simple. For classroom demonstrations in dynamical systems, I have been constructing analogue computers from op-amp circuits. Some of the circuits are of my own design, and some are copied from other scientists. All of them have been successful except for this one, by Cuomo & Oppenheim, 1993, Physics Review Journal:

![Cuomo & Oppenheim - MIT 1993](https://i.stack.imgur.com/YDNsV.png)

This circuit is designed to mimic the Lorenz Equations (rather, a re-scaled version thereof). The [x] are analog multipliers (AD633JN), and I am using NTE858M op amps. I have checked my work and I am convinced that I have built correctly. I have also verified the accuracy of the schematic, and I cannot find any discrepancy between the circuit and the corresponding dynamical system. The only output is a millivolts noise. 

Why does this implementation fail?

Here is a link to the author's paper for more detailed information:

<http://www.rle.mit.edu/dspg/documents/CircuitImplementation_000.pdf>

Answer: 
Here's is my thoughts I think that implementation might fail is because in the paper you reference, the author's use the device AD632AD multiplier while you are using the AD633JN multiplier. A quick glance through the datasheet and we can see that the AD632AD multiplier performance total error has maximum of +/-1 while the AD633JN has a multiplier performance total error has maximum of +/-2. Also the AD632 multiplier under the multiplier perfomance has a maximum Output Offset Voltage of +/-30mV while the AD633 has a maximum Output Offset Voltage of +/-50mV. It think that those differences between might be worth looking into because given the nature of chaotic system it might just be enough to modified the circuit behavior.
Please pardon it may be obvious but it seems that if you are using an oscilloscope to view the outputs be careful that you are operating in XY mode instead of just viewing each signal with respect to time.