HP 6543A, voltage set knob issue

[sairfan1]

Hi, I recently bought HP 6543A from ebay and received it yesterday,
its voltage knob is shaky though it works, i was worried if this is something i should inform seller or i can easily fix it.

thanks,

[Berni]

Its a known issue with the encoders used in these:
https://www.eevblog.com/forum/testgear/agilent-66332a-dynamic-dc-source-20v5a-repair-and-mods/msg950542/#msg950542

It probably happens if the knob gets too much of a knock from the side, but the way that the encoder is built, the top of it just falls off and they can usually be put back together.

[sairfan1]

what do you think in long run can it stop working? or its just a shaky knob but will work good.
thanks

[Berni]

No idea. I never tried to open the encoder up to see how its made inside (In fear of possibly not being able to put it back together), so i just attached the top back down to the body and called it fixed.

Im guessing trough continued knob wobbling the encoder might become even looser and stop working at some point.

These HP rack mount PSUs all tend to be very easy to take apart, so you don't have to worry about opening it up, service manual probably also shows you exactly how to get to the front panel PCB. If anything its worth cleaning out the dust inside.

[sairfan1]

I'm further trying to learn this unit,

What is CV (constant voltage) CC (constant current) and how do we switch between, just wanted to learn in what case we need these functions.
thanks,

[Berni]

Works the same as on every other lab power supply out there. The lower of the two limits is used. You might want to check Youtube for tutorials on how to use general purpose lab supplies if you don't know about these.

[sairfan1]

I checked youtube and general google unfortunately did not find resources how to use these power supplies (6543A) and what are the common functions to use.

[Berni]

I meant google how to use ANY lab power supply. This is basic functionality that all such power supplies have in some way.

The only more specific features on this particular HP supply are the "OCP" and "OV" buttons that provide over current and over voltage protection, this instantly disables the output if any of them are exceeded. How to use and test those is included in Chapter 5 "Front Panel Operation" of the user manual: https://literature.cdn.keysight.com/litweb/pdf/5959-3374.pdf?id=1000000421-1:epsg:man