I generate a 400Hz sinewave on channel 2 at 2mV p/p. The minimum. Then I turn on the 4th harmonic and H4 goes to 1.2v p/p and you can’t change the amplitude. In fact, sitting at the fundamental, if you go to any harmonic of 4 or greater the 4th harmonic comes on like this and the higher harmonic stays at zero V and can’t be adjusted. The only way you can turn of H4 is to go to H3 or lower. Firmware is 03.01.12 (latest available version)