I have a 3205, and this morning when using it i observed that channel B produces a very weird noise signal of +/- 20 mv. Any measurements taken using channel B was invalid due to the noise signal, such as a square wave from a function generator. Strangely, the scope calibration signal from the 3205's internal signal generator was displayed OK.
I tried shorting the probe tip with the clip, yet i still see +/- 20mv of noise (no change). Unplugging the probe from channel B, and the noise goes away. It may be the probe, but i swapped channel A's probe with B and the noise was still there. Only channel B has this problem. Any help on this will be appreciated.