HP8485A power sensor reads erratically

[alan.bain]

I've got a working HP 8485A power sensor and another one which I suspect is dead, but am curious as to the failure mode. Most of the dead one I have seen won't zero. This one zeros fine and can be calibrated but the reading is unstable. It's easiest to see on an analogue meter like the 435 the needle wobbles significantly (rendering it unusable of course).

Is this a known failure mode?  I'm aware they are basically unrepairable!

Alan

[Stray Electron]

  Are you sure that the problem isn't in the cable assembly?   The cable for my HP Power Meter is gimpy and sometimes works and sometimes doesn't.  And it acts the same with all of the sensors that I own.

  I don't use the meter much so I've never tried to located the bad spot in the cable or to fix it.

[alan.bain]

Good thought. I have two other cables so will try them.

Alan