New Rigol DP832A strange behaviour - broken

[Johnny_1206]

Hi,
i just received my new DP832A and i noticed something strange when i first turned it on.
Channel 1 seems to work just fine but Channel 2 and 3 are behaving very weird.

When i turn on Channel 2 with nothing connected (only my multi meter with very high impedance) it immediately goes into unregulated mode.
No matter what voltage or current limit I set, it will stay in UR-mode.
What's even stranger is, that i measure about 9V with my multi meter when channel 2 is set to 0V and i can even draw current from it.
I can run a dc motor with .5A at 9V while the channel is set to 0V.
With Channel 2 enabled and set to 5V it actually outputs about 13V (measured wit the multi meter) while displaying 4.2V.

At Channel 3 i get about the same behavior. Set to 3V it actually outputs nearly 12V (measured with the multi meter).
Without a motor connected it displays 2.8V and 0A and driving a motor it displays 1.7V and .6A.

To better explain the behavior i made this video: https://youtu.be/RRI4vehPx_A

So i assume it to be broken! How can this happen?
It can't have passed any post production testing this way!

[TurboTom]

Since channel 2 and 3 share the same ground, they also very likely share the same internal auxiliary voltage supplies. I'ld guess there's something wrong with those. I'm quite certain the PSU left the manufactuerer tested and working. The damage can have happend during transport, especially considering the workload on the carriers during this season, I suppose they're in a permanent hurry and probably applying a little less care than during other times of the year.

Since it's a newly purchased instrument, externally undamaged, return it to the distributor for a refund / replacement. Otherwise, i.e. when working normally, the DP832(A) is a very nice PSU.

...and welcome to the forum! 

[TurboTom]

...
The 832 seems to be a great PSU besides the fact that quite a few had issues with it in the past. Dave himself has blown it up at a task it actually is designed for, I think.

Yes that's correct, he published several clips about his observations and the repair. But you should keep in mind that he reviewed a rather early specimen, the manufacturer has since revised boards and components to address these "infant" problems.

The only problem that (AFAIK) still persists in a small quantity of PSUs is the tendency to reset itself once every new moon... But one of our fellow members analyzed this problem and suggested a solution for it. So far, I didn't apply that since as yet, I didn't observe the problem with my two PSUs of the DP800 series.

I agree with you though that Rigol probably doesn't run real "burn-in-testing" on their PSUs. I assume that after calibration, they run a performance test and that's basically it. What I'ld consider adequate, looking at the price of these instruments...

[bson]

Just to add to the record here, I just saw similar behavior on mine.  Ch3 was set to 5V 1A and whenever turned on even without any load on any channel would immediately bounce around in CC mode, 1-3V and about 1A (!).  Ch2 did the same but with different limits set.  Ch1 was fine, so I figured Ch2-3 had a problem I'd look at later and I continued on using Ch1.

Then, today as I got around to taking a look at it Ch2-3 behave just fine and I can't reproduce the problem.  There is an initial current spike on the first power-on, presumably to charge the output cap?  I wonder if there's a problem with this cap...