EEVblog #511 - Rigol DP832 Power Supply Teardown

[EEVblog]

What's inside the Rigol DP832 precision lab power supply. Is it identical to the DP832A
Photos: http://www.flickr.com/photos/eevblog/sets/72157635251122253/

[Hydrawerk]

Thank you for the teardown. I wonder why Rigol deletes markings on the ICs. They want the machine to be unrepairable! Does any other manufacturer do that?? I do not remember it from any Agilent scope for example...

[tinhead]

unrepairable!

no, they simply stupid. It make no sense to delete marking but leave JTAG.

That 8051, hehe, no Dave, this is KSZ8051 (Ethernet PHY) and not 8051-core based what so ever

[m12lrpv]

Thank you for the teardown. I wonder why Rigol deletes markings on the ICs. They want the machine to be unrepairable! Does any other manufacturer do that?? I do not remember it from any Agilent scope for example...

Perhaps those IC's form part of the difference with the "A" model

[marshallh]

Rigol is one of the few chinese OEMs... they don't want their design copied by cloners looking for an easy target.
It won't stop someone who's dedicated, but I'd say its not completely pointless.
It's a different mindset.

[Dread]

Rigol is one of the few chinese OEMs... they don't want their design copied by cloners looking for an easy target.

Ironic isn't it!

[Citizen]

I don't know, maybe it is just me, but teardowns getting less interesting. Every? new TT is just like one before. To be honest I was googling my own stuff while listening to Dave with one ear...
 Perhaps it is just because those teardowns are only interesting for people, who are going to buy this unit, but for others its is just another PSU. They look pretty same inside, don't they?
Routine : here is a transformer, here is a boring chip, here are caps. Nothing special for me, we saw it many times already.
The main idea of TT was to show how does interesting, unusual equipment works inside.How different, complicated problems are getting solved  by professional engineers, so  we can learn something from it. The last few TT were just dry lists of facts.
I even laughed to myself this time: "wow, even me could do this teardown , just name what you see , no special knowladge recquired"

But then again, just my humble opinion.

[m12lrpv]

Not as uninteresting as your trolling

[george graves]

But then again, just my humble opinion.

Ha!  Well, the other side of the coin is that if you're about to buy what he's tearing down(or something like it), you might watch it 2-3 times!

I know I've watched some videos more then once before making a purchase.  I think Dave is doing a great job mixing it up with test equipment and consumer stuff.

[Dread]

Yeah but as Dave says some people like it.
I would prefer tear downs of simpler devices so that the actual circuit design can be looked at it in greater detail.  You can learn so much more with just basic designs, they add to your knowledge and are useful for making your own stuff.

[RupertGo]

Well, I love linear electronics teardowns almost as much as I love RF, so I loved this one. Particularly because so much of the design was old school - although why was there no relay output isolation (which may also help with the power on excursions)? And what were the triacs doing? Crowbars? (Been a long time since I thought about that).

One point, though: the reason toroidal transformers are more efficient and radiate far less (E)MI is because of their geometry - there's nowhere for the flux to escape from, unlike the Ts and Cs and beeswax laminated core brigade. There's a lot of cool maths involved which I don't understand without far too much effort, but if anyone wants to va-va-voom with the vectors the Wikipedia page looks promising. http://en.wikipedia.org/wiki/Toroidal_inductors_and_transformers

[synapsis]

Is someone making a Dave English -> Amurrican English dictionary? I'm not quite sure what to make of "It's the duck's guts." Is that a good thing?

[tinhead]

http://www.urbandictionary.com/define.php?term=duck's%20guts

[FrankBuss]

I don't know, maybe it is just me, but teardowns getting less interesting. Every? new TT is just like one before. To be honest I was googling my own stuff while listening to Dave with one ear...

Maybe you should have listen with two ears?

Perhaps it is just because those teardowns are only interesting for people, who are going to buy this unit, but for others its is just another PSU. They look pretty same inside, don't they?
Routine : here is a transformer, here is a boring chip, here are caps. Nothing special for me, we saw it many times already.

Well, the toroidal transformer was interesting and all the constructions are different inside.

The main idea of TT was to show how does interesting, unusual equipment works inside.How different, complicated problems are getting solved  by professional engineers, so  we can learn something from it. The last few TT were just dry lists of facts.
 again, just my humble opinion.

IMHO Dave explained quite a lot, at least for beginners like me. Interesting facts about the transformer and why and where you use it, explaining the signal paths and how the boards are interconnected, explaining the power path, highlighting details which someone could use for their own designs, like covering mains voltage on the small PCB, and complaining about not so good solutions, like soldering nuts instead of using proper washers etc.

[Citizen]

Yeah but as Dave says some people like it.
I would prefer tear downs of simpler devices so that the actual circuit design can be looked at it in greater detail.  You can learn so much more with just basic designs, they add to your knowledge and are useful for making your own stuff.

I also prefer test gear,because it  normaly has more strict requierements like precision and stability. Thus you can learn how to solve this problems wisely.But PSU is just trivial and we had it alrwady many times.

[FrankBuss]

I also prefer test gear,because it  normaly has more strict requierements like precision and stability. Thus you can learn how to solve this problems wisely.But PSU is just trivial and we had it alrwady many times.

One solution would be that you don't watch PSU teardowns, if you don't like PSU teardowns.

[EEVblog]

That 8051, hehe, no Dave, this is KSZ8051 (Ethernet PHY) and not 8051-core based what so ever

Oops, yeah, that's what I get for using stuff instead of checking. 

[BravoV]

But then again, just my humble opinion.

Good , hopefully you stay humble and humbly understand and agree that your taste do NOT represent majority of the viewers. 

[jasonbrent]

... and here I am to talk about the color screen again... :-) If these are the same, that means that it's likely possible to turn a non A into an A via software and then get a full color display (yes, I realize that some like the vertical layout per channel vs. the angular layout...).

(not watched the video yet...)

-jbl

[jancumps]

I don't know, maybe it is just me...

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

[EEVblog]

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

It seems all he does is complain, so I'll no longer respond to his comments directly.
Of course, he conveniently forgets the fact that my previous teardown video (the UPS) combined whiteboard stuff with the teardown which made it quite popular. But no, that doesn't fit with his opinion that my teardowns are just the same and useless, so he ignores those ones.
This one was obviously for those who wanted to see inside the Rigol supply, and nothing more. I never claimed it be anything more.

[BravoV]

I don't know, maybe it is just me...

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

Do you mean envy as like from a competing party ?

Meh .. just look at the "attitude" at his videos, always proclaims it proudly ...  "I dubbed the video with the song I personally love so much, and it is the best song in the world, if you don't like it, screw you and you all (the audiences  ) are tasteless, go away !".

Definitely not even the same league as Dave's, let alone a competing video blogger. Its just merely an act from a very lonely individual, and very likely an attention whore too. 

[warp_foo]

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

It seems all he does is complain, so I'll no longer respond to his comments directly.
Of course, he conveniently forgets the fact that my previous teardown video (the UPS) combined whiteboard stuff with the teardown which made it quite popular. But no, that doesn't fit with his opinion that my teardowns are just the same and useless, so he ignores those ones.
This one was obviously for those who wanted to see inside the Rigol supply, and nothing more. I never claimed it be anything more.

Thanks for the look into a PS I purchased. I appreciate the effort, and I hope to see you/support you down the path you've chosen.

newb

[free_electron]

.But PSU is just trivial and we had it alrwady many times.

Really . Psu's are trivial ? You obvisously have never torn down something like a 3631 with its charge balancing adc and demuxed dac and analog optocouplers, or a 6032 resonant power supply, or a 6632 machine with down programmer or a battery emulator supply. Or a big hinking 6624a...

There is tons of shit to be learned from those beasts.

This rigol may be less i teresting but i still like to see what componets they used, how the postioned their parts on the board, what connectors are used, and other little details for construction. There is always some tidbit to be learned or something to see that may give you idea's.

[pickle9000]

I totally enjoy the teardowns, I tend to think of the people behind the design and manufacture. Look at the Siglent and Rigol rust thing. Did they know? Did they care? If they did know what would be the point at which you have to fix it? What would you do to fix it is there a chemical to stop it, and on and on. Those are real life questions and the answers will make and brake personnel and companies.   

[ElectroIrradiator]

My Mk. I eyeball claims the analog regulator schematic superficially appear similar to the standard ones use in many Agilent PSUs, which is probably not a bad thing. TL072+LM393? That plus the 3A output current limit is probably the reason for the 1000uF caps across the output rails, many Agilent supplies have those as well (with similar potentially negative effects, as mentioned by Dave).

The MCU on the top board looks like it has part of a Cypress logo in the upper LH corner, but I have no clue as to which one it might be.

If somebody else makes a tear down, then it might be interesting to get the physical dimensions of the toroid transformer, without mounting hardware and connecting wires. It looks quite large and the dimensions should give us an idea about the VA rating, which should be around 350-450VA or so.

----
Edit: Dave provided the answer to my question in a different thread. The transformer is 110 mm (dia) x 105 mm (height).

[Oracle]

Rust in a factory new equipment gear is wrong considering the amount of money you give... but maybe is not rigol fault: maybe the equipment was previously stored in a humid place by the local distributor.

[Dread]

It seems all he does is complain, so I'll no longer respond to his comments directly.
Of course, he conveniently forgets the fact that my previous teardown video (the UPS) combined whiteboard stuff with the teardown which made it quite popular. But no, that doesn't fit with his opinion that my teardowns are just the same and useless, so he ignores those ones.
This one was obviously for those who wanted to see inside the Rigol supply, and nothing more. I never claimed it be anything more.

Now that video was excellent. It had broad appeal and was an educational treat.  IMO the best teardown videos will almost always be the simple ones that can be presented in a complete dissection that demonstrates exactly whats going on in sub sections that one can use in other designs. The APC proprietary hybrid design was well worth the admission fee

[andete]

Thanks Dave for this excellent informative tear-down!

I'm just wondering, are the large output caps really a problem in practice? Would it be interesting to test?

[dougg]

Is someone making a Dave English -> Amurrican English dictionary? I'm not quite sure what to make of "It's the duck's guts." Is that a good thing?

Dave has some int-teres-ting pronunciations, even to Australian ears. Perhaps he spent some time in the land of the long white cloud ... And expressions like "in like Flynn" (referring to the long dead actor Errol Flynn's love life) are not common currency, at least not when I drove a cab in Sydney when I was a EE student. But it breaks both ways, the first time I read "dove under the table" in Canada I thought about pigeons ...

I make do with an Agilent U8001A PS which is fine for my purposes, apart from a damn loud fan. It gets around power on voltage spikes by having an output relay that is disconnected at power up until an activate button is pressed on the front panel; and I can check the voltage and current settings before pressing the activate. Perhaps Dave could test the 832's constant current performance give that large capacitor across its output.


PS Flynn was born in Hobart, Tasmania so that is the Australian connection. He died in 1959 (before Dave was born?) after a Hollywood career more noted for its off-screen exploits.

[rs20]

I've asked Rigol support, but had worse than useless (i.e., clearly completely wrong answers), so I'm going to ask this where I should have asked the whole time: eevblog forum!

Would it be safe to parallel channels two and three together, and set channel two to 30V? Clearly the channel three, maxing out at 5V, can't source any current, so it's a pointless thing to do (I'll get back to this), but what I'm wondering is would channel three actually sink current or get damaged? I see what might be considered protection diodes http://www.flickr.com/photos/eevblog/9607810872/#in/set-72157635251122253, but they appear to be parallel to the load, presumably preventing the output from being reverse biased. <aside> Also, the current shunts are on the ground side, which is a little bit funky. Does that mean that the supposedly common negative terminals have 40 milliohms between them? I just went to check, and indeed, pumping one amp through one negative terminal and out the other gives you a drop of 38mV. </aside>

The reason I'm asking is I want a supply that supplies 1 volt @ 9 amps, and then seamlessly transitions to providing 30 volts @ 6 amps.

[Christe4nM]

Thanks for doing the teardown Dave. I agree with free_electron and others that there's always things you can learn. I for one like to look at board layout, choices they've made at system level etc.

Two questions for those that like to share their knowledge:

1) If I remember correctly I thought that the E-I laminated transformers were preferred in PSUs as they provide better isolation (less unwanted coupling) between primary and secondaries compared to toroidal.

2) Can anyone explain why they need a full applications processor in this thing, alike the Agilent DMM? From my (inexperienced) point of view that seems way overkill for either instrument. Although I get that running 'real-time' datalogging, USB, Ethernet and the color screen may require a fast processor, it seems to me that the current top end microcontrollers (for example the Cortex-M3/M4) are capable enough? Am I overlooking something that I don't know about?

[Rufus]

I'm just wondering, are the large output caps really a problem in practice? Would it be interesting to test?

Yes they are a problem especially if you don't expect them to be that large. A current limit is often set to try to provide some protection for a circuit. For example you could set a 10mA current limit to test an LED and if the voltage is set too high you could kill the LED with the energy stored in the output capacitors regardless of the 10mA current limit.

[EEVblog]

I've asked Rigol support, but had worse than useless (i.e., clearly completely wrong answers), so I'm going to ask this where I should have asked the whole time: eevblog forum!

Would it be safe to parallel channels two and three together, and set channel two to 30V? Clearly the channel three, maxing out at 5V, can't source any current, so it's a pointless thing to do (I'll get back to this), but what I'm wondering is would channel three actually sink current or get damaged?

Get damaged most likely.
For a PSU to "sink" current is has to be a 4 quadrant type, which very few bench supplies are. This one certainly isn't just a regular output series pass transistor.

[RobB]

Any thoughts on the complexity of this PSU.
I am of the opinion that PSU's are among the most used and abused bits of equipment and therefore most likely to be damaged in service. I'd hate to have to trouble shoot this thing, too many proprietry components like the flex cable, unidentified components etc. I appreciate this is a precision PSU with lots of nice user features but I'd trade that for something more mundane but repairable.
Finally in the words of Niel Young. Rust never sleeps. Some cold galv paint on those raw cut edges should help.

[Citizen]

I don't know, maybe it is just me...

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

I only stated it for this video, here and on youtube, because there are two dieferent communities.
It is not obligitary rant, it is my opinion. I am not envy, why should i? Maybe you mean my tutorials?Cmon, i am not blogger, and i  not planning to be one at all.

This community reminds my a temple, where everyone worship the perfect Dave.
 Really look how agressive  users get to my  actually constructive oppinion:

Good , hopefully you stay humble and humbly understand and agree that your taste do NOT represent majority of the viewers

Meh .. just look at the "attitude" at his videos, always proclaims it proudly.Definitely not even the same league as Dave's

--ROFL, sure i am no match for  great Dave!:))
And there some angry fanatics on the youtube. I dont like this kind of cumminity.

 But to me Dave's videos are getting  less educative and more entertaining, this happens to many TV-show, even to Discovery Channel. Before you could  learn lots  from his videos: how to solder, desolder, measure, repair,layout, design, test, program, more detailed  mailbags, more unusual equipment for TT. For me the last interesting   and educative video was the JTAG FF.

I think i will just leave eevblog if anything will change. Sure not a big deal for Dave, since he has  thousands of  others  followers. But consider,  few monthes ago i was looking Dave videos with much more interests, and always gave him positive feedbacks. So something has changed since then.

[rs20]

I've asked Rigol support, but had worse than useless (i.e., clearly completely wrong answers), so I'm going to ask this where I should have asked the whole time: eevblog forum!

Would it be safe to parallel channels two and three together, and set channel two to 30V? Clearly the channel three, maxing out at 5V, can't source any current, so it's a pointless thing to do (I'll get back to this), but what I'm wondering is would channel three actually sink current or get damaged?

Get damaged most likely.
For a PSU to "sink" current is has to be a 4 quadrant type, which very few bench supplies are. This one certainly isn't just a regular output series pass transistor.

Thanks for responding, Dave! To clarify, I wasn't wanting it to sink current, was just hoping/expecting it would have a diode protecting its output and not get damanged. On your advice, I won't take that chance -- I'll get myself a schmicko Schottky and connect it from CH3+ to CH2+ and take my power from there. Cheers!

[anotherlin]

2) Can anyone explain why they need a full applications processor in this thing, alike the Agilent DMM? From my (inexperienced) point of view that seems way overkill for either instrument. Although I get that running 'real-time' datalogging, USB, Ethernet and the color screen may require a fast processor, it seems to me that the current top end microcontrollers (for example the Cortex-M3/M4) are capable enough? Am I overlooking something that I don't know about?

Yes, there wouldn't be any problem to do all the mentionned stuff  needed using a high-end microcontroller.
But my guess, developing the software is much easier with a bigger faster processor, and this "full application" processor is not much more expensive compared to a high-end microcontroller.

[jancumps]

... and maybe they needed it to drive the flashy display of the model A, and for the optional add-ons.

[baljemmett]

But to me Dave's videos are getting  less educative and more entertaining,

"But it's all right now, I learned my lesson well,
You can't please everybody, so you got to please yourself."

... or perhaps you'd rather Dave went back to driving a truck?

[anotherlin]

My Mk. I eyeball claims the analog regulator schematic superficially appear similar to the standard ones use in many Agilent PSUs, which is probably not a bad thing. TL072+LM393? That plus the 3A output current limit is probably the reason for the 1000uF caps across the output rails, many Agilent supplies have those as well (with similar potentially negative effects, as mentioned by Dave).

Agilent's PSUs are basically textbook: triac or SCR pre-regulator + series-pass transistor regulator with feedback control using opamps.
Except using a switch moded pre-regulator, or not having one, there's not much other way to design a linear supply (using a shunt style regulator maybe).
It's no suprise Rigol's PSUs look "superficially similar".

[Citizen]

But to me Dave's videos are getting  less educative and more entertaining,

"But it's all right now, I learned my lesson well,
You can't please everybody, so you got to please yourself."

... or perhaps you'd rather Dave went back to driving a truck?

But the educative content was the reason why many ppl,including me, joined EEVBLOG  few years ago. This is maybe the answer , why I started to give Dave criticism and neg. votes for last few monthes. But sure if you want to run a blog for living, you should consider the majority, and change yourself to hold the most viewers.
This happens everywhere: Discovery Channels was once very interesting and educative, but now it is switched to reality shows like Jungle/Alaska/Bering Sea Gold ,
same with BBC.

[Cdngreybeard]

The rigolna.com DP800 site has two application notes that discuss active loads and series parallel connections.

The notes confirm that the DP800 series are first quadrant supplies and that for the DP832 series channel 1 and channel 2 or 3 may be connected in series or parallel.   

The notes are an interesting read.  Check them out.

[free_electron]

Just watched the video. Here is the interesting bits my trained eye spotted

- they use flat flex from front panel to top board , then simple loose-wire connectors from top board to bottom board.... Anyone care to guess why ? Citizen maybe ? (I know why)
- milled slot around the reference diode for temperature stabilisation(thermally induced mechanical stress)
-guarded trace from the opamp to the cpu, thats more than 16 bit there ...
-that cpu is a Silicon Labs device , judging by the font of the stuff they didnt scrape off. It would match the guarded trace. Silabs has some cpus with 24 bit a/d ...
-mosfet as pass regulator element
- the big caps don't need 'goop' to tack em down as those use snap-in pins.
-look at the routing between the main cpu and its ram.. Lots of curly wurly stuff. This is ddr3 !
-noticed the text 'batteryv' close to the cpu.... This thing can have battery backup apparently... I wonder if this board may also be used in other instruments... Like their signal generators.

Stuff i learned from the video:

- there is now apprently special triac driver ics in sureface mount. Need to look that up. Last time i used a triac was 20 years ago. And probably will not use one in the foreseeable future but still the driver is nice to know. I am aware of the moc3061 zero cross optocoupler l and how to drive a triac using a small pulse transformer. Wonder what this driver ic does...

-the flatflex gave me an idea for a project i am working on (the flatflex is that white semi-rigid cable from the front panel to the top board. This is essentially a plastic tape with slats of flat copper adhered to it. Almost a flexible pcb. )

- toroids are not necesarily flat pancakes... This toroid is much taller than its diameter ... Never seen one with that aspect ratio.

So in this 'another psu' video there is plenty to be learned ! You just have to know where to look !
If i walk away learning 1 thing from a video or article, that's time well spent ! Plenty of educational value ! And i learned two things from this video (triac driver, toroid aspect). That says enough....

[BravoV]

..<snip>...

I dont like this kind of cumminity. community

..<snip>...

I think i will just leave eevblog if anything will change.

..<snip>...

Anyone care to guess why ? Citizen maybe ?

..<snip>...

If i walk away learning 1 thing from a video or article, that's time well spent ! Plenty of educational value ! And i learned two things from this video (triac driver, toroid aspect). That says enough....

Save your breath, he is leaving and that is his last post here.

[mrflibble]

Save your breath, he is leaving and that is his last post here.

Maybe to join a self-help forum, with a focus on accepting criticism without getting defensive? 

[Blaffetuur]

Thanks Dave for this excellent informative tear-down!

I'm just wondering, are the large output caps really a problem in practice? Would it be interesting to test?

would like to see a video about that !

[Mikey]

Great teardown, only thing I dont like about it, is that the device is one that I will never get my hands on

The cheap end models that are total crap compared to this is more useful, I have already used some to find what equipment to get.

[mrflibble]

Just watched it, and there was a good bit of inspiration & assorted tidbits in there. Thanks for a nice teardown Dave. 

[ElectroIrradiator]

My Mk. I eyeball claims the analog regulator schematic superficially appear similar to the standard ones use in many Agilent PSUs, which is probably not a bad thing. TL072+LM393? That plus the 3A output current limit is probably the reason for the 1000uF caps across the output rails, many Agilent supplies have those as well (with similar potentially negative effects, as mentioned by Dave).

Agilent's PSUs are basically textbook: triac or SCR pre-regulator + series-pass transistor regulator with feedback control using opamps.
Except using a switch moded pre-regulator, or not having one, there's not much other way to design a linear supply (using a shunt style regulator maybe).
It's no suprise Rigol's PSUs look "superficially similar".

 

I'm talking about the actual schematic for the series regulator, built with discrete components, not the overall method of building a linear PSU. Have a look at the schematic and PCB layout for, say, the triple rail Agilent E3631A.

For instance the Triacs are not used as pre-regulators, nor are using SCRs an option here. The Triacs are used as bipolar switches to select taps on the transformer secondaries, to limit power dissipation in the series pass device at low output voltages. In the E3631A they are triggered using optically coupled Diacs, which I suspect may be the SMDs close to the Triacs.

[Rexus]

Another great video Dave, keep them coming!

One of the questions I had was does the PS have to be so deep, couldn't they have made it shorter - well it does look like the toroidal and heat sinks pretty much determine the length, a problem for my bench sadly.

[warp_foo]

Is someone making a Dave English -> Amurrican English dictionary? I'm not quite sure what to make of "It's the duck's guts." Is that a good thing?

Dave has some int-teres-ting pronunciations, even to Australian ears. Perhaps he spent some time in the land of the long white cloud ... And expressions like "in like Flynn" (referring to the long dead actor Errol Flynn's love life) are not common currency, at least not when I drove a cab in Sydney when I was a EE student. But it breaks both ways, the first time I read "dove under the table" in Canada I thought about pigeons ...

I make do with an Agilent U8001A PS which is fine for my purposes, apart from a damn loud fan. It gets around power on voltage spikes by having an output relay that is disconnected at power up until an activate button is pressed on the front panel; and I can check the voltage and current settings before pressing the activate. Perhaps Dave could test the 832's constant current performance give that large capacitor across its output.


PS Flynn was born in Hobart, Tasmania so that is the Australian connection. He died in 1959 (before Dave was born?) after a Hollywood career more noted for its off-screen exploits.

I always thought he was trying to say In Like Flint, or an Aus variant...

http://en.wikipedia.org/wiki/In_Like_Flint

[Dread]

I think Citizen did have one valid point, the older videos are more educational (First 250) but they are also spaced much further apart, so basicaly Dave is making more video's but the educational one's come along at the same rate as before, with teardowns, mailbags and dumpster diving used inbetween to bring up the monthly total.   Fair enough deal for me, I would rather watch a mailbag episode than watch nothing at all. 

[senso]

I learned some thing new, like the routing around the voltage reference, never saw anything like that, so another thing to remenber/good to know, it seems a bit odd that it only uses one pass mosfet per rail.

[anotherlin]

I'm talking about the actual schematic for the series regulator, built with discrete components, not the overall method of building a linear PSU. Have a look at the schematic and PCB layout for, say, the triple rail Agilent E3631A.

For instance the Triacs are not used as pre-regulators, nor are using SCRs an option here. The Triacs are used as bipolar switches to select taps on the transformer secondaries, to limit power dissipation in the series pass device at low output voltages. In the E3631A they are triggered using optically coupled Diacs, which I suspect may be the SMDs close to the Triacs.

Ok, I've managed to find the schematic (p130 of service manual) of the E3631A. In this particular case, the transformer wiring is center tapped and the triacs seems to be some form of pre-regulator (feedback sensing voltage right after pass transistor). I wasn't able to find the schematic for the Rigol for comparison. Just because it uses LM393 and TL072 doesn't mean it's a "direct" copy of an Agilent schematic. Those are very common chips, TL072 are just found everywhere. Using a dual opamp (one for voltage feedback and one for current) is basically the usual way to design a pass transistor regulator.

On the contrary, I would rather think that the Agilent's and Rigol's share same ("classic") building method, but not schematic.

[EEVblog]

45min video of probing the DP832 coming up...
So much FAIL 

[jancumps]

yeah

[dr.diesel]

So much FAIL 

I'd like to hear Rigol's response, I'm sure this video won't make it on their webpage!

[Harvs]

- milled slot around the reference diode for temperature stabilisation(thermally induced mechanical stress)
-guarded trace from the opamp to the cpu, thats more than 16 bit there ...

As we don't have a proper part number for the reference (or at least I cant find what #R3A is.) What sort of class of reference and ADC would be required to build something with specs like this? E.g. could you point to an AD or LT device that might be similar league?

[ElectroIrradiator]

On the contrary, I would rather think that the Agilent's and Rigol's share same ("classic") building method, but not schematic.

From your last post I suspect we have a case of misunderstanding between us, rather than disagreeing as such. This may be due to my (ab)use of the Queen's English...?

45min video of probing the DP832 coming up...
So much FAIL 

Ouch.

[JackOfVA]

As a general comment ... I've viewed every one of Dave's videos, going back into the archives to the  first ones, over the last months and have yet to find one that didn't hold my interest enough to watch it from start to finish.

And there's nothing like a good "Dave Rant" (Trade Mark registered with IP Australia?) to enliven a video. If something is a piece of crap, Dave will say so, and that honesty is a rare quality in today's "can't we all get along" environment.

[kony]

Voltage reference datasheet: http://www.analog.com/static/imported-files/data_sheets/ADR380_381.pdf.
I just wonder, if the routed slot around is meant to reduce mechanical stress or more likely to thermally insulate the reference as much as possible from surrounding PCB. This is common for temperature sensors in SMT packages (with routed slot or at least copper keepout and raster of holes for exactly same purpose as above) used for sensing ambient temperature, but I have never seen something like that done with voltage reference. But I must admit I rather like this idea.
FR-4 is a bad heat conductor, but not as bad as air is. Correct me, if I'm wrong.

[Blaffetuur]

The only thing some people want is Dave raging about some product, but if something is good people don't appreciate it.

[Harvs]

Voltage reference datasheet: http://www.analog.com/static/imported-files/data_sheets/ADR380_381.pdf.

Thanks!  Can I ask how you found it? I used every google trick I knew and it drew blank...

[EEVblog]

The only thing some people want is Dave raging about some product, but if something is good people don't appreciate it.

Yep, or worse, they accuse me of selling out, being bought off etc. 

[alm]

Clearly. Now you've finally been unmasked as mindlessly promoting a product with a flawed thermal design. Was the check from Rigol late that you had to resort to blackmail? Or did an Agilent power supply accompanied by an even bigger check just arrive?

[kizzap]

Clearly. Now you've finally been unmasked as mindlessly promoting a product with a flawed thermal design. Was the check from Rigol late that you had to resort to blackmail? Or did an Agilent power supply accompanied by an even bigger check just arrive?

  Really? do you have naught better to do then bring people down? If Dave was being paid off for product reviews, we wouldn't be seeing issues like this come up at all. Get a fucking grip.

The only thing some people want is Dave raging about some product, but if something is good people don't appreciate it.

I very much appreciate when Dave reviews something and finds it is really good. for my first 'scope I bought a Rigol DS2072, partially because of the work of cybernet on this forum, but more because Dave took the time to review it, and also reviewed some of the other 'scopes that I was looking at, and pointed out the pros and cons of all the products.

-kizzap

[marshallh]

I think he was using some heavy sarcasm there

[EEVblog]

Really? do you have naught better to do then bring people down? If Dave was being paid off for product reviews, we wouldn't be seeing issues like this come up at all. Get a fucking grip.

I think he was joking 

[kizzap]

I think he was using some heavy sarcasm there

I think he was joking 

If he was, he got me. 

[TerminalJack505]

I'm pretty sure he was just giving a sarcastic rejoinder for those that were arguing Dave went too easy on the Rigol PSU and that he was a corporate shill.

I know that when I saw Dave's rant I had to wonder what those people would say.

[EEVblog]

I'm pretty sure he was just giving a sarcastic rejoinder for those that were arguing Dave went too easy on the Rigol PSU and that he was a corporate shill.

Of course, the truth is it's been an elaborate paid setup all along 
I praise Rigol and appear like the shill, then I purposefully bag Rigol to recover my reputation and embarrass the conspiracy theory nutters. Then Rigol come to the rescue in record time with a pre-cooked solution with the worlds best customer service, and everyone praises Rigol as the best company ever and their stock soars.
You're all being played like a fiddle 

But the real masterminds are of course the New World Order run by the big mega banks who have infiltrated the entire youtube partner system.
Why do you think I'm in the garbage room so often, it's for those clandestine cash drops in the dumpster 

[Deepak]

...with the worlds best customer service

You know, you almost had me up until this point.

[riconette]

Of course, the truth is it's been an elaborate paid setup all along 

thats the answer you schould have given that… oh what was his name? twat. 

[alm]

Why do you think I'm in the garbage room so often, it's for those clandestine cash drops in the dumpster 

So what you said in this video was true all along? You were actually telling the thruth?

[rs20]

So one thing that I noticed in the episode is that the current sense resistors appear to be on the negative rails. So I did a few tests, which I've got here in both video and text form (take your pick):



Text: So I did some tests and:
A. There's a 40 milliohm resistance if you pass current into Ch2– and out of Ch3– (which are, in theory, common/supposedly shorted out), which corresponds exactly to the theory that current has to pass through both 20 milliohm resistors to get from one to the other.
B. However, if you short-circuit Channel 3 and test for a voltage drop across Ch2–/Ch3–, it fails to materialise. If there was a 20 m? resistor between Ch3– and """true ground""" , then you'd expect to be """true ground""", and therefore Ch2–, to be 60mV lower than Ch3– at 3A. Instead, it's 0mV different.
C. Ch2– and Ch3– appear to be identical; it doesn't matter where you sink current that is sourced by Ch2+ or Ch3+, the current measurement is always spot on. So what are those resistors doing!?

I'm tearing my hair out, I can't figure out a circuit schematic that exhibits this combination of behaviours. Probably missing something obvious though!

[fridrik]

Isn't the regulation just handled on the low side on both channels, that means that the negative terminals on both channels are circuit ground. Then on each channel you would have the current sense resistor and mosfet in series with circuit gnd connected to the input circuitry (triac prereg). That however does not explain the 37 mOhm resistance you measure between the negative terminals, is it possible that it can be accounted for by just the leads internal to the supply, and the ~40mOhm is just a coincidence?

[unnecessarynitpicker]

It looks like the two sense wires are joined together in the connector in the right of the picture, but the other two supply wires do seem to go through those  20 milliohm resistors before going ?.

The grey and black wires seem to be coming from the two common terminals..

[GiskardReventlov]

Just getting around to watching past episodes.  I didn't see the siglent video but I thought it was funny to hear "yeah there's rust on this but not as bad as siglent's".  New lab equipment that has rust is really cheezy.  Who wants to buy a brand new car that's already rusting?

Lack of attention to detail in one area makes one wonder where else they've cut corners. I'm glad you mentioned it though because I'm sure they're watching.

The display is too small for me, they should have an option so that you can make one channel consume all the screen area. (maybe there is and I missed it?)  They could also just have a bigger screen by moving the channel buttons down (as Dave suggested).  Does anyone know if they've resolved all the issues that were discovered?

[mcinque]

I didn't see the siglent video but I thought it was funny to hear "yeah there's rust on this but not as bad as siglent's"

could you please link the video at the minute when Dave said it?

[GiskardReventlov]

could you please link the video at the minute when Dave said it?

It's in the teardown video, don't remember where.

[giubin]

What's the point, Citizen. You carefully put this comment both on the blog andd youtube comments.
For a few video's already.
The obligatory Citizen rant.
Blogger envy?

It seems all he does is complain, so I'll no longer respond to his comments directly.
Of course, he conveniently forgets the fact that my previous teardown video (the UPS) combined whiteboard stuff with the teardown which made it quite popular. But no, that doesn't fit with his opinion that my teardowns are just the same and useless, so he ignores those ones.
This one was obviously for those who wanted to see inside the Rigol supply, and nothing more. I never claimed it be anything more.

Thanks for your videos. You work hard and help us a lot. You help me choosing the right stuff and I learn always something. I like this Power supply.