Jason,
?? Are these hp 8924C units? A common problem with the 8924C is the on/off switch. Unlike most instruments, the 8924C turns off by a switch closure. After time on some units, the on / off switch doesn't provide a good closure so the unit turns on randomly. Lucky, the on/off switch is a DPDT and there are another set of unused contacts. I have jumper-ed the switch contacts on some so there are 2 contacts providing a closure to turn it off. If that doesn't work, the switch needs to be replaced. rick
