Hello all,
Not sure of forum rules - so I figure I'd post this and mods can move/delete if it's not the right place.
I have an Agilent U8001A power supply, which has a broken control knob. It allows me to decrement a parameter (voltage/current) but increment is very jumpy. I opened it up and probed the quadrature encoder outputs. Sure enough, one of them was noisy (transitions were not clean). I managed to get the part off the board, but there was little to identify it. After some searching on Digikey, I found the part: it's a Bourns PEC16-4015F-N0024. I'm going to replace it with a PEC16-4215F-N0024, which is the same thing but with detents (I dislike encoders without detents). Wow, can't believe Agilent used such a cheapie encoder on this supply!
Hope this helps someone else who has similar issues.