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- čas přidán 28. 08. 2013
- Dave started out wanting to investigate the power-on spike on the Rigol DP832 Lab Power Supply, but ended up hunting down a reset bug that uncovered a bad thermal design mistake in the supply.
Watch Dave hunt it down step by step, and almost get duped by some marginal oscilloscope triggering.
How will Rigol respond to this?
UPDATE: Rigol have already fixed this issue: www.eevblog.com/forum/blog/eev...
Followup video is here: • EEVblog #549 - Rigol D...
Forum: www.eevblog.com/forum/blog/eev...
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I did a project with a Chinese/Hong Kong company a while back. During initial discussion I mentioned how important power supply design was to the project. Later on, I ended up in the factory in Hong Kong in the factory. The air conditioning was running full blast and everyone wore coats to keep warm. There was the product power supply under the blast from one of the air ducts. I did the usual check for hot stuff and found one of the switcher transistors was so hot, my finger slid right off. It vaporized the grease on my finger! When I questioned the designer, his comment was it had been working fine for two weeks, what's your problem? Further subtle hints were met with similar success. A month later, the sample they sent to England caught fire, along with the computer it was attached to. I so often see power supplies with the circuit board brown from overheating and it is so unnecessary.
Regards,
Jim
For absolut maximum performance, design with absolut maximum ratings !
LOL! (I hope that was a joke...)
@@power-max well not for rigol it seems
I always like watching Daves videos and listening to his rants. I don't see his long videos as a "waste of time", as you clearly do. I see this as entertainment. I don't watch TV anymore, I watch this kind of stuff.
Thanks for the video. I watched your video yesterday and I identified a potential overheat LDO issue in our design today. That's why I really like your channel. It solves real life problems.
Awesome, I love hearing that!
I watch every video all the way through, & love 'em! keep up the great work :)
Welcome back Dave! Its nice to see you getting back to your normal self with an outrageous rant at Rigol. Glad your feeling better. Great video, thumbs up!
Thank God for techs like you. I'm retired military and worked on the repair and caibration of test equipment.The manufactures have tried to send junk to the system. We wrote it up and recommended its return, I was thinking of purchasing this type product from Teleequipment.I'm glad I didn't (although I have purchased equipment there that was OK).
I watched you unbox this Rigol and from what I have seen with the problems you have had, this is a pretty good indicator to stay away from Rigol products.
:) nice video.
I had that heat problem with my first homemade circut. I solved the problem with a bit bigger heatsink and two diodes in front of the lm317 to spead the heat dissipation over 3 components.
Others have confirmed the temperature readings, so same current is implied.
What do you mean exactly? It was shot over 2 days as mentioned in the video. No post editing voiceover or reshoots.
Well I can assure you I have tried several times to watch Mike videos, but seriously, Dave work is so much clearer and pleasurable to watch. Also Shariar vblog is absolutely top notch. I will give Mike another try don't worry, once I get the courage to do so. I tried the Ipod nano video and just had to quit after 5 minutes as it all sounded as some background noise to me... As for the Disney Channel, since they purchased Ghibli and Ardman studios, they certainly have so interesting stuff too...
Thanks Dave! I'm looking for a PS and you just saved me a lot of money.
Thankyou for this video Dave,
I purchased one of these power supplies with the upgraded resolution - Very unhappy to see this. I am getting 127 Degrees with all three channels running and very good air flow.
We are using this in a development environment that cant have failures like this. Any recommendations as to what power supply we should use with a similar spec?
WOW! and I was just about to buy one of these PS. Good thing I waited. I'll wait and see how and when RIGOL responds to this particular issue.
hey can you install a larger sync? or are you going to install a larger regulator to handle the current?
Two years down the track; and I'm wondering what the overall outcome of this was? Did Rigol do a board revision on this? Anyone know? Cheers! *Edit* Scratch that. Just watched #549 with the update about the new board with bigger heatsink.
See EEVblog #549.
After Dave found the design fault, the Rigol design guys were fired. Joking.😂
Hi Dave,
I've bought this PS and I really like it but except the lm317 issue, I've seen something else worrying.
When I connect scope probe to one of the rails of the supply (without connecting ground of the scope to anything). I see sine wave about 50 - 100 V p-p. I have put a 10 kohm resistor to power supply earth. The voltage dropped to 2 V p-p. Is this bad design or I have nothing to worry about?
awesome find Dave =)
I'd really like you to keep us updated on what happens :D
That's a real bad design flaw...
I was in Hong Kong working on a project. my part was not the ps but when I was shown the prototype I touched things. everything was OK until my finger slid off a to220. it was so hot it vaporized the grease on my finger letting my finger glide over the tab on the vapour cloud. The room temp was around 68f and air conditioning was blowing like a hurricane. tried to explain to designer this was not good with no luck. they put the case together and shipped it to England where it caught fire and burned up the computer it was attached to. some people don't get it.
It's about time you post this again. Seems like that happens about once a year.
@@xiretza3793 lolz
Fantastic rant Dave
Dave, can you put a LED on an output, current limited to 20mA and then turn off the output and back on again? I want to see if the current limiting happens fast enough to protect the output. I once had one that smoked stuff like that.
Dave, tnx for all your great videos! I noticed the heat sink on the power supply was not even close to the el-cheapo stamped one that you are getting the specs off of. Back in my day if the part was too hot to touch than MORE heat sink !!!
I noticed engineers now days save a few pennies by not providing enough heat dissipation and basically just copy n paste from the data book.
Any ways, love your videos and keep em coming !
73 N8AUM Vidas
Dave you rock!Amazing catch!
From Rigol HQ.
Do you mind if you use 43:44 in our testimonials?
Great rant Dave.
Love the rant btw! :)
I love your videos - they are really useful > thank you.
Dave your videos are awesome... Thanks a ton.. Geeky stuff is awesome... Wish there were more channels like this
The minimum input voltage for a 5V lineal regulator is approx. 8 volts. A smart fix would be to put 1N4007 diodes in series to reduce from 12V to 8 volts at the input of the regulator. With a nominal current of 0.7 A this gives a total dissipation of approx 2 watts versus 5 watts on factory design. Another option is to use a ceramic resistor in series at the reg input. Regards.
Oh, yeah, didn't notice, thanks!
What about voltage ripple from switching regulator? Is is going to be OK in this precise device?
Great video...
Would love to see it running with a proper heatsink.
Lesson learned: Don't start tracking down faults on stuff. You'll end up finding a huge heap of problems on the way.
It comes direct from the tap on the transformer, so it is what they designed it to be. 12V average with my mains input, and maybe 1V of ripple.
Did Rigol send you a new Keysight or Fluke anonymously hoping you'd use it instead? (smile) That takes balls and knowledge, finding the fault and blaming it on a poor design, far beyond the abilities of most technicians. Great video.
Just earlier today I was looking on ebay for this supply, think I'll take my money elsewhere.
Thanks Dave!
0x200th video! Great rant. Its bizarre how such precision complicated piece of equipment is let down by one of the simplest components in the entire box.
A second thought that occured to me: Have you checked whether the bridge rectifier bridge operates as it should? I remember doing a repair job where the bridge had gone nonlinear, devices downstream were running hot and 50Hz all over the place. Which is no fun when the box is an RF generator.
Thanks Dave. I'm considering the DP832A and am wondering whether this issue is present or has been fixed.
Hi, he put out a video just 2 hours after you posted this comment. It's a followup on this that shows their fix, so yes, this has been fixed.
Yea I watched that. It sounds like things are much better now.
hey friends, i have seen my friend's FLuke 12 and liked it, but now cannot find anything similar that is still in sale, can anyone help? i am looking for a compact autorange voltage and continiuity meter only
Isn't the power dissipated in the big heatsink going to be bigger when you set the output voltage to 23V instead of 30V (lowest voltage on the highest transformer tap)?
I suspect that the bounce on the 5v rail is just a symptom of the processor resetting itself. Is there a thermistor on the main heatsink? It might be watchdogging due to the lack of airflow.
What does "LXI" mean, as I see on the power supply? I have an old 80's Sears 13" TV, that says "LXI" on it, with the same exact styled X. I'm guessing obviously coincidence, but it's funny to see an old familiar logo.
LXI Consortium - LAN Extensions for Instrumentation. Didn't exist in the 80s, I'm certain :)
Would switching to a switching regulator be a reasonable fix, or do they need their digital power to be cleaner than a switching regulator can provide and thus are stuck with a linear reg?
I like Dave, he wants things done right. anyway I learned a lot here, not an engineer just a repair tech.
Could it be that perhaps the load might be drawing more current than it is supposed to?
Also the 5V regulator input terminal can be cut to insert the resistor or diodes in series to avoid modification on the original PCB,
Would it be possible to mod this yourself?
As you know what the circuit is demanding from the component Rigol chose; could you either fit a better suited one that would output less heat for the same voltage or perhaps more likely attach a custom heatsink that would offload the heat more thoroughly so it wouldn't automatically switch off?
Yeah, but doesn't explain why the reset fault goes away when cooling the reg with external fan.
Hi, please help me!
I ordered this power, but after this video, put it on hold. The seller will investigate if it has the new PCB version. If its the old I'll give up anyway.
I think about a agilent 3646a I found by usd600.
The agilent one is older, but looks 3 out of 5.
At This moment both fulfill my needs in terms of channels, voltage and current, but rigol's versatility, price and the fact that it is new, attracted me.
What would you recommend to me?!
Thanks
Rob
i am probably wrong here but i would think that if the regulator got too hot before it actually dropped out to protect itself, wouldn't it surge slightly? perhaps the main board is detecting that?
Hey great videos like. I want some information. I just bought a av receiver model yamaha rx-v475 from ebay . the receiver use 120v as power. in my country my voltage is 220-240v.. can u give me what power converter (in terms of watt amps for me to buy for this receiver.
I've used LM317's very often over the years. It's my goto regulator for any project under 1.5 amps or so. Five watts is well inside it's design parameters however, I can think of no possible reason that a designer could possibly over look the thermal consideration of venting 5 watts. I find it hard to believe that this is a design mistake!!!! I smell money. I do wonder????
Is it likely Rigol will address the lm317 issue?
750mA seems really high for the 5V rail. Can other users measure their 5V current to make sure that your unit isn't drawing more-than-designed current?
Thanks for your vids Dave!
I'll be on the lookout soon for Rigol PSUs listed as not working-for repair:)
Oh, I wonder if one of the little DC/DC converters like Recom R-78C-1.0 or similar would help as a quick workaround. It will dissipate around 0.6 W I think, Looking at the datasheet it has an efficiency of up to 89%.
will they still exchange yours because you voided the warranty by opening it?
Did they fix the issue by now?
Silly question, but cant you just drop in a more efficient DC to DC convertor that doesnt generate as much heat?
Any chance something using the 5v rail is shorting? Maybe check to see if any other components are heating up? I would guess something might if its delivering that much power. Did you ever try the upside down spray air can test? Pretty cool way of finding warm components. (no pun intended)
also i like the length of your videos and i have no problem skipping ahead if i need to. but when i have time to kill and want to learn something i watch your videos :)
They are seriously cheap, simple, and foolproof. Unless you don't calculate the dissipation properly.
Hi Dave the "funny wave you see" at 37:53
They show the false peak in Vgs due to opposite side body diode reverse recovery (just before the Vgs plateau stage)
Dave, depending on how much the unregulated voltage drops under load, the full power output may not be the worst case for the pass transistor. The worst case should be at the lowest output voltage before the first tap switch happens, at maybe 80 to 90% full current, I'd guess.
Does that mean that higher end model that shares the hardware also has this issue?
how about a lower voltage tap on the transformer?
Damn... and I really liked the look of that supply!
Put my order on hold until I see the outcome and then spent the afternoon double-checking all my own linear regulator thermals in case I've made any daft mistakes! LOL
Thanks Dave! Can I send you a bill for the increased coffee consumption?
The angry Dave is back. I was getting worried about you being so polite in your past videos. :)
Excellent video Dave, I rekon Rigol owes us a response video.
Connect it to a pan and boil water!
If the Rigol comes with the new fixed board then it should be ok. Spend more for the Agilent? - your call. It's a good supply, but only single display.
You're right I didn't notice it, but the transformer is set to right tap so that's not the point...
Even after you took the beast apart?
Before that was the Korad blowing up!
111C sitting right on a couple caps. Brilliant Rigol!
I would check that as it makes the most sense.
Does that mean that if it were plugged into 120VAC, the regulator would be getting around 6V input? (I don't know how different mains voltages are handled.) If so, the regulator wouldn't overheat here in Canada. But it also means they couldn't fix the problem by lowering the voltage of that transformer tap because then it would be too low to work on 120V mains.
The fix is easy. Use a switching 7805 replacement regulator like V7805-1500. The first time I used them they were a product of Power Trends, later bought out by TI. It was designed to be a drop in replacement for a linear 7805 (LM317) but with more efficiency and a output current of 1.5 Amps instead of the 1 Amp rating of the 7805. Simply pop out the 7805 with its heat sink solder the new part in and you're off and running.
I was thinking about for example read-back voltages will jump around etc. I dont know - It came to my mind becasue they used linear regulator for a reason....but it is possible that it was just cheaper.
It passed the Cost Accountants Review Hearing, the hell with the engineers, (smile)
Was the supply design in a country with a 110v ?
That was an awesome video.
I got hardly any feedback at all on the bookmarks last time. Most people don't even read the description let alone expand the description to use the bookmarks.
Because is takes significant time, and I have to do it different ways for youtube and the blog site. And when I get virtually no positive feedback from people using it, why bother?
What if this was made on purpose? Just to break down couple of months after warranty ends?
Dropout voltage is about 2V at that current , so it's not designed for 6V input and there's a more complicated design failure than simply doubling the input voltage.
Yes there is a 90% switcher in parallel with the linear one, but you need to pay the fee to activate it!! Ahh the days when we will see designs like that ;)
I almost wanted to buy this unit ! The features looked great, specs are awesome, price is good for an expensive hobbyist kit. Meh, thanks for the investigation ! I'll guess I'll find something else or wait for Rigol to fix this.
I generally don't bother with his videos unless they're 30 min+
Different strokes I suppose. Keep doing what makes you happy Dave, that's seems to have worked so far.
is rigol making aircos too
40:00 wearing the right shirt for today Dave
Sure is nice to have such a hug community to perform design evaluation, isn't it?
Haha, thanks, yes I am cool calm and collected most of the time :) although if that snake would have had fangs i am sure it would have been a different story! I have had some recent experiences with comments relating to time domain stuff I have been doing recently that would make be rant on a bit - that might be fun :)
By the way dave described the architecture I believe the ADC is local to each PSU channel section so that would not have an impact. In general design terms, any sensitive noise devices such as ADC's would have guarding and filtering on the supplies (resistor can cap or indictor and cap). Cant be sure without looking in more detail but thats typically how its done - mind you if they can't even get an LM317 in spec who knows...terrible design flaw for a company wanting to compete with HP!. Gerry
Why did they use LM317 ???
Nice video. Thumbs up.