Rigol DP832 smoked

[gsezz]

Hi,
I smoked both 30V Channels of my DP382. I needed more than 60V to anodize some titanium, so I connected both channels in series with yet another power supply. But dumb me didn't check the current limit on the other one, and pulled to much through the Rigol.
The big SR360 Diodes on both channels were fried. Afer replacing them, everything seemed fine again. Current and voltage limits are working correctly, once shorted out. But I get sparks on the terminals of channel 2, when I short them out.

Any suggestions?

[bd139]

I'm surprised it failed. I've seen TTI power supplies doing this for a decade with no problems at all and running into full short all the time.

Added DP832 to my personal hardware shitlist.

If you see sparks that's probably the output capacitors discharging. Totally normal. All my supplies do that.

[Damianos]

I'm surprised it failed. I've seen TTI power supplies doing this for a decade with no problems at all and running into full short all the time.
...

It was not shorted but a high current "pushed" thru it!

[bd139]

Should still survive it.

[2N3055]

Should still survive it.

It shouldn't..

He connected another (unspecified) power supply in series, pulled god knows how much current, and most of all maybe over 100V all together with all 3 PSU in series...  And who knows  how much reverse voltage into outputs.

These types of PSU (including all of Keysight and all other brands) are not meant to be used that way, and in manual it strictly says so.

[Jeroen3]

I can't find it in the manual.
It does say:

Note: Make sure that all the channels in series connection are working in constant voltage mode. If one of the channels is working in constant current mode, the other channels will enter critical state in which their outputs are unpredictable.

Other lab supplies I have specify maximum voltage of the circuitry above ground. I recall one being 60V.

[gsezz]

I guess one could be of the opinion that there should be a fuse in the output path. But I'm not the guy who blames a manufacturer for his own mistake. Rigol soulnd't have to plan for an idiot who pushed about 60A thru a 3A rated device. I wasn't to concerned abput the voltage, since I only needed 2-4V more to get the color right. I've done it before, without any issue, but this time I just forgot to set the current limit on the second supply.


Should't the capacitors be discharged thru a resistor? Channel one has a big 5.1k resistor acros the terminals, directly behind the shunt. There are also two resistors of same type on the channel 2 board, but since the traces are covered by a big heatsink, I can't tell how they are conectet. There is no conectvity between any bigger resistor and the ch2 terminals.

[JxR]

The Rigol DP832 has a max of 240VDC above ground, with a limit of 3A connected in series.  Connecting multiple power supplies in series should be fine, just so the maximums are observed (and the specifications are accurate).  As the owner stated though, the other power supply did not have its current limit set appropriately.  So, I can only assume the 'other' power supply was sourcing more than 3A.  60A would definitely be a problem

Regardless, sounds like the damage was already identified and repaired.  The diodes did their job, and the owner has a working DP832 again.

[rstofer]

If there are bleed resistors across the output capacitors, perhaps one of them is fried.  It wouldn't keep the PS from functioning but perhaps the capacitors wouldn't be discharged.  I don't know if there is a resistor or not.

[gsezz]

I managed to remove the heatsink and found the right resistor. It's also 5.1k directly across the terminals, behind the shunt. I measured it out of circuit and it's fine. Now I'm really confused.

[2N3055]

If you put outputs at say 30 V, and current limit at 10mA, when you short the output it should spark. You are discharging large output capacitor. If it doesn't spark,  capacitor is damaged.. Of course when disabling channel it should discharge..

[gsezz]

It sparks on any voltage and current setting, even 0.5V. I've never seen this on any Lab Supply before, only on cheap fixed voltage supplys.

edit. Nope, sorry, it only sparks at higher voltages. I don't know what I did earlier, when it sparked at 0.5V. I might have set the wrong channel to 0.5V, I don't know. I rarely operate it above 12V, that propably why I've never seen the Rigol spark before.
So, I think my supply is fine. ..I hope.

Thank you guys.

[2N3055]

It sparks on any voltage and current setting, even 0.5V. I've never seen this on any Lab Supply before, only on cheap fixed voltage supplys.

That is funny... Do you have oscilloscope?

[bd139]

Should still survive it.

It shouldn't..

He connected another (unspecified) power supply in series, pulled god knows how much current, and most of all maybe over 100V all together with all 3 PSU in series...  And who knows  how much reverse voltage into outputs.

These types of PSU (including all of Keysight and all other brands) are not meant to be used that way, and in manual it strictly says so.

Fair point - misread original post. I stand corrected!

[JDubU]

See attached Rigol app note about connection of active loads.

[JxR]

This should also be viewed:

"Two or more isolated channels of one power supply or multiple power supplies can be connected to provide higher voltage or current".
https://rigol.desk.com/customer/en/portal/articles/2283507-increasing-voltage-or-current-by-using-multiple-power-supplies-

There is nothing inherently wrong with connecting multiple power supplies in series, and it is fully supported.  You just have to observe the maximum ratings (and use the minimum of those between the two different units).  It already sounds like the owner realizes the their error (not limiting the other power supply to 3A). Of course, read what the article says and don't put the supplies in a circuit that is going to put them into CC mode. 

Safest bet is to look for a specific power supply that can provide the current levels you need for the size of your titanium piece, and voltage levels for the color you want.  If the piece is very small, you may even be able to get the look you want by connecting 10-12 9V batteries in series if you don't plan on anodizing titanium often.