HED Faults - causes and prevention?

Good Morning/Afternoon/Evening,


I have seen several instruments obtainined a HED error/fault during sequencing or during the tuning process. These instruments have been in various cuontries with varying electrical output, but all protected by high spec. UPS systems.


Occasionally the HED fault disappears for a while and functions normally then reappears agian maybe a month or two down the line. The HED volts are fine and below 1500 V (with a limit of 2500 V).

What causes these faults to occur?


I have also seen HED faults occur and the only way to fix them is to replace the HED power supply located in the MS circuit board case. We have tried changing the horns first but the issue was still there until the power block was replaced.


Again what are the causes for this issue? As we don't know why this is happening so we don't know how to prevent it.

Parents Reply Children
  • Hi Ron,


    We have changed them ourselves with great success on 4-5 instruments. We still have the power supply blocks from the modules.

    On opening there are no obvious signs of damage (but most of the component is kept in an epoxy resin, assuming to prevent any arcing or dust on the high voltage components).


    Unfortunately Agilent only operate through 3rd party contractors in some of the countries we have the MSD's in.


    Can you think of any way these can get damaged through normal use?





Was this helpful?