Author Topic: EEVblog #512 - Rigol DP832 Bad Design Investigation  (Read 321918 times)

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Offline sync

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #200 on: August 31, 2013, 07:39:50 pm »
Wow, you guys are great, I'm sure that if we all give it our best we can come with a way to kill it. Seems like that's what we're trying to do anyway....

I thing it's an important question for a lab power supply. Can it be killed? Under which circumstances? What's happen then? Does it output 50V without any current limitation? Look at the Korad review.

The Rigol has a terrible failure in it's thermal design. Why should i trust the design regarding this small pass transistor?
 

Offline lilshawn

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #201 on: August 31, 2013, 07:59:55 pm »
i'm not seeing a really big deal here...worse comes to worse, open 'er up and if you have the first revision board... put a big ass heatsink on it. relocate it if you have to. 20 minutes out of your life tops.
 

Online madires

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #202 on: August 31, 2013, 08:10:44 pm »
You could replace it with a switcher, but it wouldn't be a drop in job. It would be a re-layout of that part of the board. I'd probably use a switcher which had a switch frequency above 500kHz, which simplifies some parts of the EMC design.  I've had some luck using LM2734's, but their output current is limited to around 1 amp.

I'm using the LM2576 (52kHz, 3A) with an additional output ripple filter without any problems for several toys with "antennas" attached. EMI tests are done with a shortwave receiver :-) The EMI is so low it's really hard to detect any or distinguish it from background noise. But that would add about 5 bucks to the BOM.
 

Offline FatalError3141

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #203 on: August 31, 2013, 08:22:56 pm »
i'm not seeing a really big deal here...worse comes to worse, open 'er up and if you have the first revision board... put a big ass heatsink on it. relocate it if you have to. 20 minutes out of your life tops.

Yea, granted its not a large problem to fix. But you don't expect to buy a £400 Supply that you have to "fix" before using it. 

I found another issue with this supply, could someone else confirm it?  Turn the outputs off while in the storage menu and they will remain active  :wtf:
 

Offline brainwash

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #204 on: August 31, 2013, 10:39:50 pm »
Just watched the video and short of replacing the LM317 with a bigger regulator and/or bigger heatsink the better solution would be to replace it with a switched supply (those 2$ ones on ebay should work well after a thorough check) as a preregulator to 6.5-7V and the heatsinked LM317 after it. It's a 15 mins and 3$ job compared to sending the unit over or causing it to fail and having to wait for another.
At least that's what I would do.
 

Online tom66

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #205 on: August 31, 2013, 11:29:41 pm »
The LM317 doesn't have particularly good ripple rejection though, so you've still got the wideband noise problem that a cheap switcher will give.
 

Offline stormbr

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #206 on: September 01, 2013, 12:08:00 am »
Dave, can you say your serial number ?

My power supply not have problem with noise when reset the dp832.

s/n: DP8C1512XXXX

I live on brazil and the cost to send was 200 u$ and 200u$ of taxes, i not pay this again to send for warranty.

:S
« Last Edit: September 03, 2013, 01:40:24 am by stormbr »
 

Offline Dread

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #207 on: September 01, 2013, 02:53:01 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.

Corporate666 do you work for Rigol or are you the forums official attack dog when anybody has something negative to say?

First of all how could I have had a conclusion about the 832 before I even saw the first video?  I had never even heard of the DP832 until Dave did the first video!   Based on that video I made it very clear that I did not like the "DP832 Precision Power Supply" and stated my reasons why.  How do you then come to a conclusion that I have an "irrational hatred" of it when my initial reasons are not even under dispute?

Dave did not like the rotary encoder design or the numeric pad, I did not like the rotary encoder or Pad.

Dave did not seem pleased with the way the encoder responded, I did not like it at all.

Dave did not like that Nasty glitch, I did not like it either.

During the video it was clear that the set voltage versus the output voltage under no load did not correspond, I said I did not like that at all, is something wrong with that opinion.

The video showed one of the outputs having a small current draw when nothing was connected, that's another issue I did not like.

No sense voltage on a precision power supply, whats a person supposed to do, dedicate a precision meter to monitor the DUT?

And my main reason was that I did not like the ergonomics of the design and the incorporation of so many rarely used features because I knew it was just a selling point distraction that would mean less design money would be available for making a supply that was actually going to be precise and reliable.  The Teardown and the First video proved that to be correct.

Quote
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.

Yes it is terrible and for the reasons I stated above!
My agilent knob fits nicely between my two fingers and I can turn it very slowly and precise while looking at my other equipment, something that seems very difficult to do with that encoder.  It also tracks my movements perfectly and the display matches my every movement, the 832 does not do that.

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

Really!!  They sound either upset or worried and several have pointed out other issues. 

Quote
Case in point... you say "what Dave thought, only he knows".  No, we all know what he thought because he told us.
I assumed Dave opened the box for the first time while filming the video, he made many positive remarks and some negative remarks.  Most people don't make up their mind about anything that they see for the first time until they mull it over for a few hours, sometimes days. That's why snap purchases are typically regretted.  So it was logical to assume that Dave's opinion could be in Flux so I had no way of knowing what he thought the next day, his mind might have changed. That's why I simply stated only Dave knows.

Quote
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.

Yes; it is pretty clear to me!  That's my opinion, in your world is there no room for people to have opinions that differ from yours?

"You have no idea why I hate it":  I stated the reasons in every post |O

"The thermal problem is a deal breaker for you":  For some people they may not see it as a deal breaker at all, they may just stick a bigger heat sink on it or just keep the Lid on and sell it in 2 years.  Once again "Deal Breaker" is your opinion and it's not shared by everyone.  My opinion was formed from the first video because I have already been reemed up the arse buying equipment that had lots of dazzling features at the expense of being really bad at doing the core thing it was designed to do.

Whats the bloody point of having a Blinged out Linear Precision Power Supply if it's not Precise and it's not reliable?  :palm:

And all those "Benefits" you think I should be praising are bloody useless if it's primary functions don't work properly :-//

Corporate666 why don't you spend your time on the bloody rude people I see making posts on this forum instead of hammering people like me who are just trying to have a civil discussion.

You seem to be tracking my posts, so tell me how many times have I said a reviewed piece of equipment was a POS?  It would also be helpful to know if that's not allowed on the forum because it sure feels that way.
The Optimist says the glass is half full, the Pessimist says its half empty, an engineer only see's a glass that’s twice as big as it needs to be!
 

Offline teda

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #208 on: September 01, 2013, 03:20:25 am »
Dave will probably get an official fix from Rigol and if I paid 400$ for a piece of equipment I would want one too.

In a pinch instead of adding a bigger heat sink or adding a switcher regulator, another solution could be a 4 ohm / 5watt resister in series with the regulator input to bleed off some of the input voltage.
 

Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #209 on: September 01, 2013, 04:36:37 am »
Yes; it is pretty clear to me!  That's my opinion, in your world is there no room for people to have opinions that differ from yours?

I am not attacking you at all - but I call it like I see it, and when I see bullshit, I call it bullshit.

I don't know what you mean "tracking your posts"?  I just remember that you and that Citizen guy seemed to have a beef with the supply (and/or Dave) and have been grinding out that beef in the threads on it.  You overstate every negative aspect of the unit and downplay every positive aspect to fit your conclusion that it's shit and Agilent is better.  You don't even own one of these PSU's and have never used one but you are arguing with folks that own both, and you seemed to get very offended when people criticized Agilent.

One of my other hobbies is racing cars, and the same thing happens on all the car forums.  The Mustang guys spend eons arguing with the Corvette guys that their car is better.  The Corvette guys argue the same to the Viper guys.  The Viper guys argue the same to the Ferrari guys.  And the Ferrari guys argue the same to the McLaren guys.   

There are some who just appreciate all the cars (or power supplies), and when those folks see someone waging a war against a product, it's pretty clear.  As it is in this case.  You don't like this PSU - we get it, so don't buy one.  But feel free to keep telling us all how it's total shit and only an Agilent is worth buying and every feature the Agilent lacks is unnecessary and every feature the Rigol has is unnecessary  :-DD
It's not always the most popular person who gets the job done.
 

Offline mickpah

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #210 on: September 01, 2013, 05:00:20 am »
Yes; it is pretty clear to me!  That's my opinion, in your world is there no room for people to have opinions that differ from yours?

I am not attacking you at all - but I call it like I see it, and when I see bullshit, I call it bullshit.

I don't know what you mean "tracking your posts"?  I just remember that you and that Citizen guy seemed to have a beef with the supply (and/or Dave) and have been grinding out that beef in the threads on it.  You overstate every negative aspect of the unit and downplay every positive aspect to fit your conclusion that it's shit and Agilent is better.  You don't even own one of these PSU's and have never used one but you are arguing with folks that own both, and you seemed to get very offended when people criticized Agilent.

One of my other hobbies is racing cars, and the same thing happens on all the car forums.  The Mustang guys spend eons arguing with the Corvette guys that their car is better.  The Corvette guys argue the same to the Viper guys.  The Viper guys argue the same to the Ferrari guys.  And the Ferrari guys argue the same to the McLaren guys.   

There are some who just appreciate all the cars (or power supplies), and when those folks see someone waging a war against a product, it's pretty clear.  As it is in this case.  You don't like this PSU - we get it, so don't buy one.  But feel free to keep telling us all how it's total shit and only an Agilent is worth buying and every feature the Agilent lacks is unnecessary and every feature the Rigol has is unnecessary  :-DD

kind of agree and it nearly as annoying as this
 

Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #211 on: September 01, 2013, 05:07:41 am »
Yes; it is pretty clear to me!  That's my opinion, in your world is there no room for people to have opinions that differ from yours?

I am not attacking you at all - but I call it like I see it, and when I see bullshit, I call it bullshit.

I don't know what you mean "tracking your posts"?  I just remember that you and that Citizen guy seemed to have a beef with the supply (and/or Dave) and have been grinding out that beef in the threads on it.  You overstate every negative aspect of the unit and downplay every positive aspect to fit your conclusion that it's shit and Agilent is better.  You don't even own one of these PSU's and have never used one but you are arguing with folks that own both, and you seemed to get very offended when people criticized Agilent.

One of my other hobbies is racing cars, and the same thing happens on all the car forums.  The Mustang guys spend eons arguing with the Corvette guys that their car is better.  The Corvette guys argue the same to the Viper guys.  The Viper guys argue the same to the Ferrari guys.  And the Ferrari guys argue the same to the McLaren guys.   

There are some who just appreciate all the cars (or power supplies), and when those folks see someone waging a war against a product, it's pretty clear.  As it is in this case.  You don't like this PSU - we get it, so don't buy one.  But feel free to keep telling us all how it's total shit and only an Agilent is worth buying and every feature the Agilent lacks is unnecessary and every feature the Rigol has is unnecessary  :-DD

kind of agree and it nearly as annoying as this

 :-DD

I am soooo going to log into my computer remotely on Monday, crank the volume up and play that clip when I leave for work.  Everyone will hear it but won't want to go into my office and mess with my computer  :-DD
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Offline free_electron

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #212 on: September 01, 2013, 05:45:33 am »
in itself there is nothing wrong in useing that lm317. they just should have bolted on amuch larger heatsink. okay you are burning off 7 watts.. so what ? its a 300 watt+ power supply. who cares ...

agilent uses the same lm317 in their 363x supplies. but , they bolt them to the main pass transsitor heatsinks. and those things are huge , fan cooled and never heat beyond 50 degrees c , even under full supply dissipation

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Offline mickpah

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #213 on: September 01, 2013, 06:00:32 am »
yep, the LM317 gets too hot. I'm bored about now
Let replace it with this http://bursonaudio.com/DIY_Super_Regulator.html

the audiophools vouch for them so they must be good  >:D

that being said enough trolling for today from me.
 

Offline TMM

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #214 on: September 01, 2013, 07:12:38 am »
I can't see how Rigol can get out of replacing affected units. Back when the XBOX 360 was having overheating issues and MS were only offering an extended warranty the standard advice was to wrap your console in a towel to force it to overheat so you could make a claim.
The towel method was a dodgy way of reflowing the solder on the BGA lol which could actually fix it temporarily.

Every time I look at a piece of gear from China I look at how many bells and whistles they have added and I try to subtract that from what I figure the cost price is and then calculate out how much money they must have spent on the core engine of the device.

To me the Core is what really matters, what’s the point of having a Precision Lab Power supply with 100 bells and whistles if it’s output is not really precise or reliable?

When I saw the DP832 I knew the core engine had to be made on a very low budget, the rotary encoder knob was the first indication that money was very tight and it only got worst as I saw more.  I think if Dave was to look around further I think he would find that regulator is probably just one of many shortcuts they took to save money.  I would bet good money that almost every part in that unit from the regulators to the Caps are all picked from the lowest bidder and very little margin is built into the overal design.

BTW it was nice to see the Fluke 87V were it belonged, front and center.

Great Video Dave.
What about the DS2000 series scopes and DG4000 function gens which happen to be both cheap and well designed? There is hardly a corner cut in those products. Rigol usually pick brand name parts. So what if they pick an ST reg over Linear Tech? ST is still better than some unknown chinese reg.

I think the issue in the DP832 was a genuine design oversight, not the result of cost cutting. The person responsible for the powersupply board with the 5v reg may have only ever been intended it to supply something like 200mA and the team designing the digital board just asked what kind of regulator was on the board, got the answer of it being an LM317 and assumed that they were fine because their board only drew 700mA.
The surprise is that no one picked up on it before the product went out the door.

Regardless of the LM317 issue, upon seeing Dave's first review video of the DP832 i felt that Rigol had dropped the ball a bit. Particularly ergonomics which is one thing they usually do well. Clearly the design team that did the DP832 is not of the same calibre as the team(s) which have engineered other Rigol products such as the scopes and function gens.


« Last Edit: September 01, 2013, 07:16:04 am by TMM »
 

Offline Salas

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #215 on: September 01, 2013, 09:48:08 am »
Why a mosfet as a series pass element?

Alexander.

Safer-easier. No secondary breakdown.
 

Offline eternal_noob

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #216 on: September 01, 2013, 10:20:36 am »
Hi

A better fix for the voltage regulator would be to change the transformer winding, from the hunt for the problem there looks to be +8v a drop across the regulator, no reason to have so much voltage drop, 4 volts would give lots of margin while dropping the power dissipation in half. With the larger heat sink things would be be just right.

If you mean lowering the currently used transformer tap output, that would mean re-winding the transformer (basically, making a new one). Hardly an optimal solution. If you mean using another tap which is already there used for the main output, well, the point is to have the logic supply (and the interface ports) separate and galvanically isolated from the main outputs. Anyway, most fans are rated 12V and I strongly assume this one is 12V as well.

If a buck winding will fit on the transformer without any problems physically, it should do the trick. Plus an extension on the heat sink of course.
 

Offline eternal_noob

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #217 on: September 01, 2013, 10:26:08 am »
The LM317 doesn't have particularly good ripple rejection though, so you've still got the wideband noise problem that a cheap switcher will give.
I believe the datasheet says something about 70db rejection and that should be pretty good.
 

Offline Steffen

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #218 on: September 01, 2013, 10:35:35 am »
Is the USB host port powered by this LM317 too? Then load it with an additional 500mA.>:D

For what you need 500mA on that PSU to power USB devices? Is there any need to plug in a 2,5" HD to save few lousy KiB for some settings or configuration data? I think flash drives are more handy in this case - and even cheaper!
 

Offline dr.diesel

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #219 on: September 01, 2013, 10:41:39 am »
For what you need 500mA on that PSU to power USB devices?

To charge my cell phone.

Offline con-f-use

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #220 on: September 01, 2013, 11:49:04 am »
500mA is the USB specification on max. current draw so the PSU better provide it!
 

Offline salviador

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #221 on: September 01, 2013, 11:58:48 am »
who designed this product is an intern?
 :--
 

Offline salviador

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #222 on: September 01, 2013, 12:00:54 pm »
Dave, please, hack your 832 , how to resolve these bug?
« Last Edit: September 01, 2013, 12:06:37 pm by salviador »
 

Offline brainwash

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #223 on: September 01, 2013, 12:13:20 pm »
The LM317 doesn't have particularly good ripple rejection though, so you've still got the wideband noise problem that a cheap switcher will give.

If you look at Dave's video you can see there is actually plenty of ripple after the LM317; the ripple seemed to increase with temperature.

Sure, you can stick a larger TO220 and heatsink to the whole thing but any added consumer (like USB) will force the part some more and result in high inefficiency. I would still stick a switched preregulator before the LM317.

Rigol has agreed in the comments that there has been an oversight in the design. Admitting to the error or issuing a "fix" might result in a class lawsuit so they would likely try to avoid that and instead say something about "stability improvement modification".
 

Offline sync

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #224 on: September 01, 2013, 12:21:31 pm »
Is the USB host port powered by this LM317 too? Then load it with an additional 500mA.>:D

For what you need 500mA on that PSU to power USB devices? Is there any need to plug in a 2,5" HD to save few lousy KiB for some settings or configuration data? I think flash drives are more handy in this case - and even cheaper!

It's not about using a HD or not. The power supply should not reboot if the USB port is loaded. Like a computer. What do you think of a computer which will crash when a USB port is loaded/overloaded?
 


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