Hanks
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Hanks Two FG-100 DDS Generators were purchased. One had distorted waveforms, even worse than shown above, at over 1KHz while the 2nd. had clean waveforms right up to 100KHz. I compared the 2 PCB assemblies and you can see that the good one had been resoldered after manufacture. The design of this unit is excellent, the manufacture looks good, but when tested, it is obvious that the SMT assembly temperature was too low or the belt moved too fast thru the flow oven. This is typical of the ROHS no-lead solder that requires higher heat to solder than the lead-based solder. So the solder looks good but it has not adhered to the solder pads of the components. By simply resoldering the parts manually on the top of the PCB assembly, everything works OK. I am referring only to the 2 Op-Amps (LM358 or TL022) and resistor/capacitor parts on the output stage. With both the good and bad DDS, the outputs of the microcontroller chip thru the resistor networks, were excellent waveforms. If you want to see photos, contact: us@soundeffx.com