This issue will most likely become a moot point in the coming weeks as I was, moment ago, informed we are upgrading our HPLC system.

However, currently we are running a Waters 6000A pump system with a LDC spectromonitor III UV/Vis detector. All of this is controlled by a Waters automated gradient controller. We have an HP 3395 integrator for data logging. :(

When I start our pump, warm up the detector lamp, and turn on the controller I hit the plot command on the integrator in order to verify a decent baseline. While running the plot a consistent square wave is generated by the integrator. To return to normal the solution I've found is to turn off the controller and individually flush each pump. After which I can turn the controller on again and the plot shows a stable, flat baseline.

Any ideas of a possible cause or others experience similar issues with similar equipment? Anyone still using these?
Thanks All