Author Topic: EEVblog #512 - Rigol DP832 Bad Design Investigation  (Read 321933 times)

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Offline Stonent

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #250 on: September 02, 2013, 06:00:29 am »
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.

I've seen more of those than I'd care to count. It was the ones with AMD cpus with Nvidia chipsets. Pretty much any of their laptops made with that combo during that time had it.  Also Dell D630 and E6400 laptops had overheating Nvidia chips.
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Offline Stonent

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #251 on: September 02, 2013, 06:01:56 am »
"Dave Nader"  :-+

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Offline riconette

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #252 on: September 02, 2013, 06:03:21 am »
… isn't the unit shunting enough heat away from the regulator with the current air flow?

the airflow, the amount of air, the heatsink size and the amount of heat to be transported away from the lm317. so… which parameter you'd like to change for better performance?
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Offline FrankBuss

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #253 on: September 02, 2013, 06:04:19 am »
People seem to be advocating (including the actual rigol fix) to install a larger heatsink but isn't the unit shunting enough heat away from the regulator with the current air flow?
No, Dave demonstrated that it heats up to 109°C, even with the air flow from the fan and closed case, see minute 13:46 in the video. The voltage regulator and capacitors will age very fast at this temperature. If the regulator dies, it can even short the 12V input to the output and destroy the digital electronics, and it could catch fire, if the fuse is not tripping.
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Offline Stonent

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #254 on: September 02, 2013, 06:11:50 am »
I'd be curious if you could either put a capacitor to smooth the ripple when it starts overheating to see what happens, or find a way to reproduce that rippling current with function generator feeding into a transistor. So not really overheat it but simulate the effect on the 5V rail to trigger the logic to reboot it again.

Did you also ask them about the reversed color on the + and - ?
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Offline Zbig

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #255 on: September 02, 2013, 09:29:02 am »
the airflow, the amount of air, the heatsink size and the amount of heat to be transported away from the lm317. so… which parameter you'd like to change for better performance?

There's nothing that can be done, I'm afraid:

- You were made as well as we could make you.
- But not to last
- The light that burns twice as bright burns half as long. And you have burned so very very brightly, Rigol


Sorry, but I just couldn't help myself after realizing that's a "Blade Runner" owl as your avatar!  ;)
 

Offline riconette

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #256 on: September 02, 2013, 10:29:56 am »
There's nothing that can be done, I'm afraid:

- You were made as well as we could make you.
- But not to last
- The light that burns twice as bright burns half as long. And you have burned so very very brightly, Rigol


Sorry, but I just couldn't help myself after realizing that's a "Blade Runner" owl as your avatar!  ;)

you're welcome :)
now its time to squish home heads and poke some eyes!
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Offline riconette

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #257 on: September 02, 2013, 12:29:24 pm »
I had a reply from my supplier:

Quote
this topic is already past. The 2nd series with the transformer, there was DP832 and thus problems with the voltage regulator, because the supplier had supplied the wrong transformer. This problem is already fixed and the affected devices have been replaced or changed the transformer. So was immediately known and has been fixed.

(translated from German)

seems we both have the same supplier.
on the other hand… rigol may have been aware of the problem, but they sold the defective units anyways. so i'm going to check which revision the upper board has when my unit arrives.
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Offline gilbjd

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #258 on: September 02, 2013, 02:04:28 pm »
I doubt whether there are DP832 power supplies with Rev 3 boards in the supply chain yet. Correct me if I'm wrong.

I bought my DP832A on 20 August this year. Its serial number starts DP8B1529XXXXX (29th week of 2013) and its factory calibration date was 8 August 2013. It clearly has a Rev 2 board as the 2 electrolytic capacitors, the LM317 and its heat sink are visible through the ventilation holes in the Rev 2 positions. The heat sink runs at just over 100 degrees Celsius as judged by sticking a thermocouple through the ventilation holes.
 

Offline FrankBuss

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #259 on: September 02, 2013, 03:14:47 pm »
For what it's worth I am in the UK but bought the PSU from Germany. Out mains seems to be about 240V still, and Germany is probably still 220V, but Europe is supposed to be harmonized on 230V. So any 230V transformer they ship to Europe could be producing +/- 0.4V on a 9V tap, but that should be okay.
I've just measured it: 226.7V here in Cologne with my HM8012 (0.4% accuracy for the 500V AC range, true RMS).
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Offline madires

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #260 on: September 02, 2013, 03:27:48 pm »
For what it's worth I am in the UK but bought the PSU from Germany. Out mains seems to be about 240V still, and Germany is probably still 220V, but Europe is supposed to be harmonized on 230V. So any 230V transformer they ship to Europe could be producing +/- 0.4V on a 9V tap, but that should be okay.
I've just measured it: 226.7V here in Cologne with my HM8012 (0.4% accuracy for the 500V AC range, true RMS).

Had anything from 225 up to 235V over the last years. Some seconds ago it was 227V (north of Frankfurt/Main).
 

Offline gilbjd

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #261 on: September 02, 2013, 03:37:44 pm »
I bought my DP832A on 20 August this year. Its serial number starts DP8B1529XXXXX (29th week of 2013) and its factory calibration date was 8 August 2013. It clearly has a Rev 2 board as the 2 electrolytic capacitors, the LM317 and its heat sink are visible through the ventilation holes in the Rev 2 positions. The heat sink runs at just over 100 degrees Celsius as judged by sticking a thermocouple through the ventilation holes.

Interesting. You are 230V 50Hz, same as Europe. That implies that the problem isn't fixed. I will try to do a better thermocouple reading on my unit.

We're 240V 50Hz here in Australia. Where I live the mains is usually around 245V RMS.
 

Offline Zbig

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #262 on: September 02, 2013, 04:01:50 pm »
I don't think the difference in mains voltage is enough to account for the overheating. What we really need to know is if European units have a different transformer to Australian units, and what supply voltage the 7805 is supposed to be on.

The mains voltage selector on the back would suggest they don't.
 

Offline Zbig

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #263 on: September 02, 2013, 04:15:43 pm »
Which in turn reminded me to provide a hint for the Rigol (well, any dual-voltage PSU for that matter) owners. When I got my Siglent SPD3303S it turned out the distributor remembered to switch the primary to proper voltage (230V) on the back but forgot about the fuse. Siglent specifies 6.3A for 120V and 3.15A for 230V operation respectively, which of course makes perfect sense, but the dealer forgot to switch the fuses so I was on 6.3A one for some time. I was positively surprised to find that there's a convenient spare fuse storage space in the IEC socket/fuse socket combo which contained the 3.15A fuse for me to switch. So check yours, 230V guys, just to be on the safe side.
« Last Edit: September 02, 2013, 04:19:49 pm by Zbig »
 

Offline Tepe

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #264 on: September 02, 2013, 04:27:59 pm »
For what it's worth I am in the UK but bought the PSU from Germany. Out mains seems to be about 240V still, and Germany is probably still 220V, but Europe is supposed to be harmonized on 230V. So any 230V transformer they ship to Europe could be producing +/- 0.4V on a 9V tap, but that should be okay.
I've just measured it: 226.7V here in Cologne with my HM8012 (0.4% accuracy for the 500V AC range, true RMS).
I just measured 240.3 V here (north of Germany).
 

Offline nigel53

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #265 on: September 02, 2013, 05:04:43 pm »
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.

I'm surprised that this idea hasn't had any more discussion.  It's potentially the cleanest and easiest DIY solution to this problem.  If the center area of the transformer is open, you might only need 10 to 15 turns of wire to make a buck winding to drop the voltage to the proper level.  You might even be able to thread the new wire in without disconnecting all the other windings.

Has anyone checked this out?

Ed

If you have access around the core, looking at the mounting in Dave's video, I doubt it. You then need the specification for the toroidal fitted (Max temp. rise above ambient, max ambient temp etc.) to even spec. the added winding correctly for temperature, will it pass the insulation tests as per original? I wouldn't class this as the easiest DIY solution, any modifications involving any items connected to the mains supply are fraught with potential hazards

That's a surprisingly cautious attitude on this forum!  :)  You can't tell from the pictures if there's room or not.  Someone would have to undue the mounting nut and look.  Temperature rise is a non-issue.  We're only talking about a few watts on a transformer that's rated for 400 or 500 watts.

Insulation testing is also a non-issue.  The transformer has all the necessary insulation.  The extra winding will be outside everything else and so, protected by the existing transformer insulation.  Even though it will be connected in series with one of the existing windings, that winding already has the necessary ratings.

Ed

Adding another winding of a few watts is not the point! You are adding a winding around an item that could be specified for a typical temp. rise above ambient of 50 deg C, this thing could run at 100 deg C.
The extra winding would indeed be outside everything else, including the existing transformer insulation; were talking about insulation to chassis, not just to the mains input.
 

Offline SeanB

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #266 on: September 02, 2013, 06:06:51 pm »
If I bought one I would put a bigger heatsink on it, and as well change the little 100uF 35V capacitor on the output of the 317 to a 470uF 16v unit. Add a 6V8 1W zener across it as well as a sacrificial device in case of failure of the 317, as there is a 2A PCB mount fuse there ( thanks for including that and not skimping Rigol, very useful to actually not rely on the big mains fuse for protection only) that will blow as the zener dies a horrible death as well, saving the digital board.

As well I would bend those fins of the heatsink further to allow airflow along it, and turn them to restrict airflow less.
 

Offline Kjelt

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #267 on: September 02, 2013, 07:05:14 pm »
If Rigol has fixed this issue they can better rename the v2 to  DP833 or higher since no-one is gonna buy this hot number anymore .
 

Offline plesa

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #268 on: September 02, 2013, 07:46:06 pm »
I quite impressed how many of members who purchased this crappy power supply is going to repair it by yourself.
I really do not understand why not to return unit to Rigol distributor, this will make the pressure on them.
 

Offline bitwelder

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #269 on: September 02, 2013, 07:52:47 pm »
I don't think the difference in mains voltage is enough to account for the overheating. What we really need to know is if European units have a different transformer to Australian units, and what supply voltage the 7805 is supposed to be on.
Would it make sense to compare the weight of the PSUs (for those who don't want to break the warranty seals)? It seems there are at least two transformers used with with this unit, a 400VA and a 500VA. I would guess that the units with a 500VA transformer are sensibly heavier.
 

Offline ElectroIrradiator

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #270 on: September 02, 2013, 08:03:21 pm »
I quite impressed how many of members who purchased this crappy power supply is going to repair it by yourself.
I really do not understand why not to return unit to Rigol distributor, this will make the pressure on them.
Quote from this page on cognitive dissonance:

"(...) A more common example of cognitive dissonance occurs in the purchasing decisions we make on a regular basis. Most people want to hold the belief that they make good choices. When a product or item we purchase turns out badly, it conflicts with our previously existing belief about our decision-making abilities. (...)"

Also see irate comments directed at anyone trying to discuss the bigger issues behind these minor technical problems.
 

Offline c4757p

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #271 on: September 02, 2013, 08:08:10 pm »
Not necessarily cognitive dissonance. If I bought a power supply that had a problem, I'd probably want to fix it myself just because I can do it faster. Who wants to wait for warranty repair on something like a power supply? It's not like it's some whiz-bang Agilent scope, there's nothing in there I can't repair by myself.

And even if it's faulty, there's a lot of stuff in there that's not faulty. I would still consider it worth the $400 even if I had to take an hour to fix a regulator.
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Offline Corporate666

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #272 on: September 02, 2013, 08:24:12 pm »
I quite impressed how many of members who purchased this crappy power supply is going to repair it by yourself.
I really do not understand why not to return unit to Rigol distributor, this will make the pressure on them.
Quote from this page on cognitive dissonance:

"(...) A more common example of cognitive dissonance occurs in the purchasing decisions we make on a regular basis. Most people want to hold the belief that they make good choices. When a product or item we purchase turns out badly, it conflicts with our previously existing belief about our decision-making abilities. (...)"

Also see irate comments directed at anyone trying to discuss the bigger issues behind these minor technical problems.

I think people get frustrated because of assumptions like in this post.

For example, what are the "biggest issues" behind these problems?  Rigol designed a PSU with an idiotic bug that should never have left the QC room.  But how is that symptomatic of bigger underlying issues?  The PSU works as advertised and performs within spec.  That's what I expect of a PSU.

As for people not returning them, it's a rash assumption to say it's because people want to believe they are good.  In my case, the power supply still works and performs the job I bought it to do.  It's not actually defective.  It's just that we disagree (with Rigol) with the way in which the PSU was designed.  I don't think Rigol (or their distributors) would accept the units back on the basis that we don't like how something was designed, at least not without a restocking fee.

In my case, I bought from TE and their return policy is 7 days with a restocking fee for non-defective units.  Good luck arguing the case that a PSU which performs as sold is defective because one does not agree with a design decision that may cause it to fail earlier than we would like.  That's not going to happen.  And even if they did take it back, what do we ask for in exchange?  A refund?  A different PSU?  A version 3 of the DP832?  Until and unless Rigol acknowledges this as a warranty issue, no resellers are going to preferentially sell customers Rev3 models.

There's not even any indication that if any units fail, they will be fixed/replaced with the Rev3 model.

Isn't the smart choice, at this moment, to wait to hear an official response from Rigol, and then users can choose to either A) wait until it breaks and send it for repair B) Preventatively fix it themselves or C) "encourage" it to fail within the warranty period, after the Ver.2 units are gone so they will get it repaired/replaced with a Ver.3 unit instead?



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Offline ElectroIrradiator

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #273 on: September 02, 2013, 08:37:54 pm »
Not necessarily cognitive dissonance. If I bought a power supply that had a problem, I'd probably want to fix it myself just because I can do it faster. Who wants to wait for warranty repair on something like a power supply? It's not like it's some whiz-bang Agilent scope, there's nothing in there I can't repair by myself.

And even if it's faulty, there's a lot of stuff in there that's not faulty. I would still consider it worth the $400 even if I had to take an hour to fix a regulator.

I don't entirely disagree. However, I at least (this crowd is a bit unusual here) don't have the ability at home to fix or perhaps even just diagnose potential issues with BGA solder connections, or if for instance the transformer was found to be fundamentally flawed. Many people won't be able to get warranty repairs nor replacements, once they have opened a product. In this case it seems we are lucky in that a fix to a few problems are easily DIYable, but you cannot rely on this always being the case.

Which to me would suggest people are better off in the long run to tell the manufacturer to fix their stuff, so it performs as advertized. Even if it takes longer.

I think people get frustrated because of assumptions like in this post.

For example, what are the "biggest issues" behind these problems?  Rigol designed a PSU with an idiotic bug that should never have left the QC room.  But how is that symptomatic of bigger underlying issues?  The PSU works as advertised and performs within spec.  That's what I expect of a PSU.

The bigger issue is the one I and others have raised on various occasions recently (and got thoroughly told off for doing so): People need to focus on basic performance of the test equipment they buy first, bells and whistles secondly. Otherwise the manufacturers will focus on making more (inexpensive) bells and whistles, instead of focusing on basic performance (which can be costly to implement correctly).

The reason why I in particular mentioned this some days ago, is that I have seen a scenario very similar to this one play out before, almost 30 years ago. To me what happens here feels a bit like a deja vu slow motion train wreck.

I had decided to let the subject rest for a bit, in the hope that I might be wrong. But there you go...

As for people not returning them, it's a rash assumption to say it's because people want to believe they are good.  In my case, the power supply still works and performs the job I bought it to do.  It's not actually defective.  It's just that we disagree (with Rigol) with the way in which the PSU was designed.  I don't think Rigol (or their distributors) would accept the units back on the basis that we don't like how something was designed, at least not without a restocking fee.

In my case, I bought from TE and their return policy is 7 days with a restocking fee for non-defective units.  Good luck arguing the case that a PSU which performs as sold is defective because one does not agree with a design decision that may cause it to fail earlier than we would like.  That's not going to happen.  And even if they did take it back, what do we ask for in exchange?  A refund?  A different PSU?  A version 3 of the DP832?  Until and unless Rigol acknowledges this as a warranty issue, no resellers are going to preferentially sell customers Rev3 models.

There's not even any indication that if any units fail, they will be fixed/replaced with the Rev3 model.

Isn't the smart choice, at this moment, to wait to hear an official response from Rigol, and then users can choose to either A) wait until it breaks and send it for repair B) Preventatively fix it themselves or C) "encourage" it to fail within the warranty period, after the Ver.2 units are gone so they will get it repaired/replaced with a Ver.3 unit instead?

I would agree, that in the current situation the smart move for any buyers would be to do nothing right now, while we wait for Rigol's next move.
 

Offline c4757p

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Re: EEVblog #512 - Rigol DP832 Bad Design Investigation
« Reply #274 on: September 02, 2013, 08:51:20 pm »
Not necessarily cognitive dissonance. If I bought a power supply that had a problem, I'd probably want to fix it myself just because I can do it faster. Who wants to wait for warranty repair on something like a power supply? It's not like it's some whiz-bang Agilent scope, there's nothing in there I can't repair by myself.

And even if it's faulty, there's a lot of stuff in there that's not faulty. I would still consider it worth the $400 even if I had to take an hour to fix a regulator.

I don't entirely disagree. However, I at least (this crowd is a bit unusual here) don't have the ability at home to fix or perhaps even just diagnose potential issues with BGA solder connections, or if for instance the transformer was found to be fundamentally flawed. Many people won't be able to get warranty repairs nor replacements, once they have opened a product. In this case it seems we are lucky in that a fix to a few problems are easily DIYable, but you cannot rely on this always being the case.

I agree about the BGA part. No matter how much I try I cannot properly remove and solder a BGA chip. |O But does this even have any BGAs? (I don't remember from the teardown.) They're probably the least likely part to fail in something like this, so even though I'd be up the creek without a paddle if I voided my warranty and one of those broke, I doubt it would.

I'd probably cuss a lot about having to fix the transformer, but I'd do it. Another unlikely problem. (Yes, I see it's part of the problem here, but I'd probably just replace the 317 with a bodge board containing an LM2575.)
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