Author Topic: EEVblog #512 - Rigol DP832 Bad Design Investigation  (Read 267786 times)

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Offline envisionelec

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #150 on: August 30, 2013, 09:56:25 pm »
Hey Rigol - I'll gladly buy dozens of these power supplies....for YOUR cost!

:)
 

Offline tom66

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #151 on: August 30, 2013, 10:17:36 pm »
Why am I telling this story ? well the firmware update changes just one thing....it slowed the zoom motor and effectively lowered its current consumption. It appears that the battery in the SX280 is overloaded by video and Zoom functions operating at the same time and drops its p.d. as a result. Oooops !

Reminds me a little of the "infamous" HP dv6000 fix... these laptops are prone to having the lead-free solder on the GPU fail due to the laptop running hot. The HP "fix" makes the fan run at 100% all the time, which probably puts failures just outside of the warranty period and turns the laptops into miniature jet engines.
 

Offline centon1

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #152 on: August 30, 2013, 11:09:03 pm »
Dave I can't thank you enough for everything and especially these reviews. My DP832 was to ship this coming Tuesday Sept. 3rd.
I've canceled it.
 
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Offline EEVblog

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #153 on: August 30, 2013, 11:19:39 pm »
While I was not one of those "twelve year old trolls" and I have made No such accusations about Dave, I would point out that this Video certainly had a different feel about it than Dave’s normal video's and I am pretty sure it was partly meant to address those people directly!

As always, those who try and read intent into my videos fail miserably, every time.

 

Online xrunner

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #154 on: August 30, 2013, 11:24:09 pm »
I watched the whole video yesterday, now there is 11 pages of posts, so forgive me if this has been asked.

I was wondering why they just didn't mount the regulator on a much bigger heat sink? Seems like there is enough room. That doesn't excuse the shitty electrical design, but metal isn't real expensive and if they had settled on the electronic part already seems like an easy way to buy more thermal capacity.

But you guys are better at this than I am.  :-//
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Offline AlfBaz

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #155 on: August 31, 2013, 01:08:41 am »
I don't know much about these matters but given a precision power supply board that goes to the trouble of using guard traces and stress relief on the reference, why would you then want to go and place a switcher on the same board to produce nearly an amp?

Not only would they have to contend with noise on the supply board but those gulps of current are being drawn from the same transformer that's supplying the DC out. Seems to me that using a switcher here would almost defeat the purpose of designing a linear lab supply in the firs place

Edit: oh and using only that one pissy series pass element seems a bit dodgy as well
« Last Edit: August 31, 2013, 01:10:53 am by AlfBaz »
 

Offline wizzy

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #156 on: August 31, 2013, 01:17:57 am »
It's all to a price level.
Lots of companies have issues from time to time due to oversights and mistakes.. This is built to a very nice price level and they have worked towards fixing it. They provide a 3 year warranty, pretty good for this price level. There is too much risk of issues for them to be purposefully cooking the capacitors.

If you aren't content or don't understand what you are buying here then go spend $2000+ on a different brand, or grab the siglent.

I'll be putting an order in for one when I can be guaranteed the newer model board and I suspect that it will perform more than adequately for my purposes.
 

Offline TerminalJack505

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #157 on: August 31, 2013, 01:20:42 am »
I watched the whole video yesterday, now there is 11 pages of posts, so forgive me if this has been asked.

I was wondering why they just didn't mount the regulator on a much bigger heat sink? Seems like there is enough room. That doesn't excuse the shitty electrical design, but metal isn't real expensive and if they had settled on the electronic part already seems like an easy way to buy more thermal capacity.

But you guys are better at this than I am.  :-//

That's what they wound-up doing.  Somewhere in this or the other thread Dave posted a picture of a new board layout.  The heatsink is bigger and has been moved away a bit from the caps.

And, yes, it should take care of the problem so long as it's big enough.  I've been applying the thermal modeling information Dave taught in one of his videos.  I pretty much just guessed at some of the numbers but they're probably pretty close.  Making the heat sink's thermal resistance smaller has a dramatic effect.
 

Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #158 on: August 31, 2013, 02:37:48 am »
[While I was not one of those "twelve year old trolls" and I have made No such accusations about Dave, I would point out that this Video certainly had a different feel about it than Dave’s normal video's and I am pretty sure it was partly meant to address those people directly! You can read into that what you want, in any case I liked the teardown a lot.


I think you (or rather they, if you are not one of them) flatter yourself if they think Dave is adjusting the tone or content of his videos to address one or two outspoken trolls.

I have a much more reasonable explaination - occam's razor.  Dave really liked the power supply.  Dave really didn't like the power supply thermal issue.
« Last Edit: August 31, 2013, 02:40:13 am by Corporate666 »
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Offline Fsck

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #159 on: August 31, 2013, 03:23:18 am »
well, the rest of the PSU looks pretty good.
But that restarting thing is really crippling
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Offline mickpah

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #160 on: August 31, 2013, 04:05:29 am »

They will be replacing all Australian units, I don't know about other countries.

I would not call this a proper belt'n'braces fix, as I think the heatsink still isn't big enough, but it probably now puts it into the (just) acceptable category.
They have also apparently made a few other fixes.
this restores my confidence a bit, but I think I owe you a thanks Dave.
Call me cynical but I don't think there would have been any action without your BS call

I really don't think they sourced a heatsink, modified the board, and had it produced and tested in just two days..
no, not the fix, I can bodge a new heatsink or switching regulator myself- this is what I wanted to hear "They will be replacing all Australian units" interesting a sales slime somewhere else knee jerk reaction was to blame counterfeit part - without this sort of publicity it would have been swept under the carpet. "Dave Nader"  :-+
 

Offline SeanB

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #161 on: August 31, 2013, 04:59:12 am »
Probably there were a range of boards in stock with some being V2.0 and some V2.1 or later ,and as the cost of scrapping the existing V2.0 stock is high, and they will do the job for basic use with the likelyhood of failing in the warranty period being small ( few people will draw 500mA from the USB to drive a flash drive, at load it will run cooler with a high fan speed, most will be in a cool airconditioned environment) some bean counter calculated the chances of failure are small, and this would be within the allowed warranty return value. However now they have had it shown, so have to do something to either replace the boards, or to have a field modification kit to add a bigger heatsink or a small modification board to replace the whole power supply.

I hope as well they have fixed the swapped colours on the power leads to the front panel, it can be confusing to the authorised service centre people that have to repair them.
 

Offline Dread

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #162 on: August 31, 2013, 06:02:08 am »
[While I was not one of those "twelve year old trolls" and I have made No such accusations about Dave, I would point out that this Video certainly had a different feel about it than Dave’s normal video's and I am pretty sure it was partly meant to address those people directly! You can read into that what you want, in any case I liked the teardown a lot.


I think you (or rather they, if you are not one of them) flatter yourself if they think Dave is adjusting the tone or content of his videos to address one or two outspoken trolls.

I have a much more reasonable explaination - occam's razor.  Dave really liked the power supply.  Dave really didn't like the power supply thermal issue.

This power supply as noted by the numerous posts and the original video has so many issues that the thermal issue is just the icing on a rather nasty cake!  What Dave thought after the first video only Dave knows. I know that I was completely turned off by the terrible rotary knob design and its tracking, the ergonomics of the unit as a whole and the voltage display not showing the exact set voltage plus that nasty spike.  The list goes on but surmise to say it was pretty clear to me from the original video that the power supply even before the tear down was not that good, of course that's just my opinion.  I guess we will know for sure what Dave was thinking if he keeps the repaired revision as his main bench supply.
« Last Edit: August 31, 2013, 06:09:29 am by Dread »
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Offline EEVblog

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #163 on: August 31, 2013, 06:57:01 am »
What Dave thought after the first video only Dave knows.

I thought I said what I thought?
It seemed like a pretty decent supply for the money. I liked (mostly) the way it worked, I liked (mostly) the features, I liked (most of) the build quality. It had a couple of small issues, plus the small power on spike, but overall, no show stoppers. It wasn't bad, esp compared to the POS Atten it replaced. As always, YMMV.

 

Offline EEVblog

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #164 on: August 31, 2013, 06:59:22 am »
this is what I wanted to hear "They will be replacing all Australian units"

As I clarified, that statement was incorrect, due to a mis-communication.
 

Offline mickpah

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #165 on: August 31, 2013, 07:49:33 am »
this is what I wanted to hear "They will be replacing all Australian units"

As I clarified, that statement was incorrect, due to a mis-communication.
bugger missed that. wait patiently I guess, still has warranty, but would rather be preemptive , Mr Murphy says it will fail at the worst possible time otherwise
 

Offline eksund

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #166 on: August 31, 2013, 07:56:50 am »
I was in the mode of ordering the DP832 after Dave:s review. The price is right and the functionality is to my need.
Then I saw the follow up and decided to wait for answers.
I can´t buy a power supply who has a fault in its power supply.
I have now asked the dealer to verify that the units they have are of later edition.

I can´t wait for Dave to update with a video about the new boards performance.

Thanks!
 

Offline JoeO

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #167 on: August 31, 2013, 08:21:19 am »
Maybe the DP832 was released as a way to get rid of the dodgy DP832A boards.
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Today, only 26,000 remain.
 

Offline Harvs

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #168 on: August 31, 2013, 09:16:57 am »
As a complete aside to this linear reg issue, here's the bit I don't get.  You go to all this trouble to build a 0.05% spec PSU, then don't put separate sense terminals on it?  What's the point in having all that accuracy if you still need a separate meter to know what voltage your DUT is getting?
 

Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #169 on: August 31, 2013, 09:23:30 am »

This power supply as noted by the numerous posts and the original video has so many issues that the thermal issue is just the icing on a rather nasty cake!  What Dave thought after the first video only Dave knows. I know that I was completely turned off by the terrible rotary knob design and its tracking, the ergonomics of the unit as a whole and the voltage display not showing the exact set voltage plus that nasty spike.  The list goes on but surmise to say it was pretty clear to me from the original video that the power supply even before the tear down was not that good, of course that's just my opinion.  I guess we will know for sure what Dave was thinking if he keeps the repaired revision as his main bench supply.

You had your conclusion in mind before you ever saw the video, and before you ever knew the specs of this supply.  I noticed you have an irrational hatred of it and inflate every criticism to be the worst thing ever, and gloss over every benefit as useless.

Case in point... "terrible rotary design".  I don't know what is terrible about it?  It is better than the knob on my Agilents.  There is nothing wrong with it's tracking.  It works great.

Case in point... you say "as noted by many posts has numerous issues".  The comments from owners have been overwhelmingly positive. 

Case in point... you say "what Dave thought, only he knows".  No, we all know what he thought because he told us. 

Case in point... you say "pretty clear to me it was not that good". 

You have hated this power supply from day one... I have no idea why.  But it clearly has very little to do with this power supply itself.  The thermal problem IS a deal breaker, but your complaints predated that discovery by a long time.
« Last Edit: August 31, 2013, 09:39:36 am by Corporate666 »
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Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #170 on: August 31, 2013, 09:25:00 am »
this is what I wanted to hear "They will be replacing all Australian units"

As I clarified, that statement was incorrect, due to a mis-communication.

Do you know if Rigol are still looking into this (or at least your distributor is) and expecting to get back to you? 
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Offline nack

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #171 on: August 31, 2013, 09:30:30 am »
Let me comment on the voltage readback-lag a little. Some argue this needs to be fixed and is a flaw in the design. Although the voltage readback from the outputs is a little laggy when you rotate the adjustment wheel and change the set output voltage, if you actually measure the change of output voltage and watch the smeller indicator of the set-voltage you are adjusting, it pretty much adjusts instantly. At least as quick a my 87V display readback shows me.

So yeah, although the readback on the supply is annoyingly laggy, it's good to know the voltage adjustment responds quickly to user input, and corresponds nicely with the smaller voltage-set readout on the display.
 

Offline open loop

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #172 on: August 31, 2013, 10:12:06 am »
I think the main point of the video was "how did this get past design review!" Dave was going to have this power supply as a "keeper" in the lab as that this is a nice supply for the money. Ok it had some small issues but this would not have mattered to most users. The worst of which was the voltage power spike which I think he wanted to look into.

What really upset him was what we all now know, the 5v power circuit overheated which somehow caused a reset and closely placed smoothing caps to a very hot heat sink. In short poor design - something that is garanteed to get David ranting.

Rigol were obviously aware of this well before David's PSU was shipped because a fix was emailed back 5 minutes after David's question. And that fix would have taken a week or two at least to design and verify. So the key questions to my mind are,

1. How did this get past design review or the first, second round of product verification and testing?

This I have no answer for this as only Rigol can answer this, all of my guesses would be meaningless drivel.

2. Why was the product not pulled before first shipments?

The answer to this only Rigol can know but we can only guess and there are several reasons that come to mind, we only just noticed the problem (see question 1), or wanting to "save face" and not admit it publicly and deal with any issues with warranty as I would have imagined that they have a warranty fund provided by the bean counters.

3. Does the fix address the original problem?

Can't answer this until we see a news from Rigol and somebody independently verifies this. Again Rigol is key to this.

And finally

4. How is Rigol going to handle this with existing customer's?

This is key for Rigol and if they handle this well then this will put them at an advantage above their competitors. But as we have seen they have spent many thousands of man hours building a reputation and one silly design mistake can ruin all of that.

This is where the company needs say "I don't want to save some money, I want to save my reputation, I will do all this needed to make this right". They could learn something from the way Microchip responded to Dave's review of the PIC kit 3.

Imagine being the design engineer where you had several projects on the go and this was somehow missed. As I am sure David would verify that part of being the design engineer is to having to fix errors that you did not foresee or were not listened to during the design review. And this impacts on your current 6+ projects. This even worse when the damn thing is the field all over the world.

Anyway I get the feeling that Rigol is a relatively new company and this maybe the first time they have had such a serious issue. It will be interesting to see how this turns out.

BTW The hello kitty version of this PSU doesn't have the reset issue ;-)

 

Offline ali80

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #173 on: August 31, 2013, 10:14:25 am »
I think the maximum power dissipation in the pass transistor should occur at output voltage of 22v and not 30v, just before the tap changing by the triac.
and by the way, why using discrete taps like the old relay based designs while you can have a continuous tap by using the triac?
 

Offline Zbig

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #174 on: August 31, 2013, 10:58:27 am »
I think the maximum power dissipation in the pass transistor should occur at output voltage of 22v and not 30v, just before the tap changing by the triac.
and by the way, why using discrete taps like the old relay based designs while you can have a continuous tap by using the triac?

I think it would be much harder to get rid of the noise you get by regulating AC with a triac (basically, you're chopping off more or less of the middle section of the sine wave, while keeping its peaks). Plus, chances are there would be annoying audible noise (ever had a triac-based lights dimmer?)

EDIT:
Furthermore, I don't think that short, intermittent current pulses (which you'd get by regulating secondary's output with a triac) is an optimal way of loading the transformer.

EDIT 2:
Basically, if you chose to go that route, I think you'd be better off just designing a proper switching mode supply as essentially you've just offset all the benefits of a linear supply anyway.
« Last Edit: August 31, 2013, 11:36:03 am by Zbig »
 


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