Rigol DP832 smoked - Page 1
Forum section: electronics / testgear

author: gsezz
author_rank: Newbie
timestamp: May 28, 2019, 10:16:47 am
content: 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?

author: bd139
author_rank: Super Contributor
timestamp: May 28, 2019, 10:43:47 am
content: 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.

author: Damianos
author_rank: Frequent Contributor
timestamp: May 28, 2019, 11:14:16 am
content: Quote from: bd139 on May 28, 2019, 10:43:47 amIt was not shorted but a high current "pushed" thru it!

author: bd139
author_rank: Super Contributor
timestamp: May 28, 2019, 11:33:07 am
content: Should still survive it.

author: 2N3055
author_rank: Super Contributor
timestamp: May 28, 2019, 11:55:04 am
content: Quote from: bd139 on May 28, 2019, 11:33:07 amIt 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.

author: Jeroen3
author_rank: Super Contributor
timestamp: May 28, 2019, 01:15:49 pm
content: I can't find it in the manual.It does say:QuoteOther lab supplies I have specify maximum voltage of the circuitry above ground. I recall one being 60V.

author: gsezz
author_rank: Newbie
timestamp: May 28, 2019, 01:47:14 pm
content: 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.

author: JxR
author_rank: Unknown
timestamp: May 28, 2019, 01:53:04 pm
content: 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 problemRegardless, sounds like the damage was already identified and repaired. The diodes did their job, and the owner has a working DP832 again.

author: rstofer
author_rank: Super Contributor
timestamp: May 28, 2019, 01:56:41 pm
content: 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.

author: gsezz
author_rank: Newbie
timestamp: May 28, 2019, 02:11:35 pm
content: 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.

author: 2N3055
author_rank: Super Contributor
timestamp: May 28, 2019, 02:21:31 pm
content: 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..

author: gsezz
author_rank: Newbie
timestamp: May 28, 2019, 02:31:54 pm
content: 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.

author: 2N3055
author_rank: Super Contributor
timestamp: May 28, 2019, 02:36:23 pm
content: Quote from: gsezz on May 28, 2019, 02:31:54 pmThat is funny... Do you have oscilloscope?

author: bd139
author_rank: Super Contributor
timestamp: May 28, 2019, 02:59:39 pm
content: Quote from: 2N3055 on May 28, 2019, 11:55:04 amFair point - misread original post. I stand corrected!

author: JDubU
author_rank: Frequent Contributor
timestamp: May 28, 2019, 04:22:19 pm
content: See attached Rigol app note about connection of active loads.

author: JxR
author_rank: Unknown
timestamp: May 29, 2019, 12:00:53 am
content: This should also be viewed:"Two or more isolated channels of one power supply ormultiple power suppliescan 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.