Last month I was using a DRS4 evaluation board to digitise the signal from the charged particles in piM1 beam line at PSI. The beam in piM1 is a mixture of pions with a small percentage of protons. Pions are close to minimum ionising and were producing the signals on the order of 250 mV (Landau distributed). The protons at this momentum (250 MeV) are not minimum ionising and produced much higher signals ( I could not exactly measure them because they were of scale for the DRS4 board). The pulses were on the order of 0.5 usec long. At low rate (~1kHz) the board was able to handle them, but when I turned the rate of particles to about ~300 kHz, the channel went flat. My question is whether the evaluation board has some type of input protection that would be possible to replace? Or does that mean that I have burned the input of the DRS4 board itself? Other channels behaving normal.