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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 !

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!

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.

Thanks Dave! I'm looking for a PS and you just saved me a lot of money.

Fantastic rant Dave

They are seriously cheap, simple, and foolproof. Unless you don't calculate the dissipation properly.

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.

awesome find Dave =)

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).

Dave you rock!Amazing catch!

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.

Great rant Dave.

Dave your videos are awesome... Thanks a ton.. Geeky stuff is awesome... Wish there were more channels like this

Others have confirmed the temperature readings, so same current is implied.

Lesson learned: Don't start tracking down faults on stuff. You'll end up finding a huge heap of problems on the way.

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

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...

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.

Love the rant btw! :)

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.

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????

I love your videos - they are really useful > thank you.

Oh, yeah, didn't notice, thanks!

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.

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.

I'd really like you to keep us updated on what happens :D That's a real bad design flaw...

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.

Almost certain they didn't do it deliberately. If they did, they wouldn't already have the fixed board in the pipeline

Connect it to a pan and boil water!

Before that was the Korad blowing up!

Great video... Would love to see it running with a proper heatsink.

What do you mean exactly? It was shot over 2 days as mentioned in the video. No post editing voiceover or reshoots.

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.

Yeah, but doesn't explain why the reset fault goes away when cooling the reg with external fan.

Also the 5V regulator input terminal can be cut to insert the resistor or diodes in series to avoid modification on the original PCB,

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?

That was an awesome video.

Just earlier today I was looking on ebay for this supply, think I'll take my money elsewhere. Thanks Dave!

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.

Nice video. Thumbs up.

Have you noticed if things aren't perfect Dave rants on and on. but that's because he takes a lot of pride in his work and wants to do things right.

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 :)

I like Dave, he wants things done right. anyway I learned a lot here, not an engineer just a repair tech.

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.

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 :)

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?

Doesn't matter. Even a genuine one would be operating outside it's max recommended die temperature range.

Unfortunately, all the big name manufacturers are making those crappy thin tabbed TO220's now! ST and ON both are doing it. We use the tab for mechanical support and can't do it now. They call the new package "single gauge" and the old thicker tab "dual gauge" tabs in the datasheet, btw. I bet this saved the manufacturer a lot of money since most of the cost is the copper in that tab.

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

Excellent video Dave, I rekon Rigol owes us a response video.

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 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.

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%.

Not really. If they don't like it they generally just don't talk to me again!

Should have split the voltage drop across two lm317's with seperate heatsinks. You don't drop all the way from 12 to 5 if you are going to be drawing any reasonable amount of current. Thankfully though, LM317's are self regulating and will turn themselves off before they burn themselves, but still.

You're right I didn't notice it, but the transformer is set to right tap so that's not the point...

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.

I'll be on the lookout soon for Rigol PSUs listed as not working-for repair:)

Could it be that perhaps the load might be drawing more current than it is supposed to?

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.

hey can you install a larger sync? or are you going to install a larger regulator to handle the current?

Why would I replace the heatsink? Why would I want to impromptu fix a brand new unit that has a long term design fault? The unit worked with the lid on, no need to fix anything right now. I waited to see what Rigol had to say about it and it turns out they are replacing all units. Replacing the heatsink would have been a stupid and pointless, if I even had a suitable size and shape heatsink in stock to begin with.

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.

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.

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.

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)

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 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?

Somehow it's getting common to use 7805 or just LM317 as a 5V rail regulators, but why on earth do you need to give it like ~12V, I saw even ~20V in some TV, the poor thing just unsolder itself from board. In few words they just look in data, ahh 1A current that's enough for us, but totally forget to make up simple math over it.

It will not only be the DP832 that is affected, the 832A will have the same problem if they are sharing the same board.

The angry Dave is back. I was getting worried about you being so polite in your past videos. :)

111C sitting right on a couple caps. Brilliant Rigol!

As an interim fix why not pre regulate the 12V down to say 9V with a 7809 or similar and spread the thermal load across two devices. The best solution would be to find a lower voltage secondary tap. Even the output supply taps seem rather generous 54V to get 30V out, A lot of wasted power right there, at least a few trips to the moon by Dave's standard. This vid has restored my faith in Dave. I was thinking he was a bit of a Rigol fanboy. Guess that theory is blown.

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!

Agilent supplies have always been the ducks guts if price is no object.

From Rigol HQ. Do you mind if you use 43:44 in our testimonials?

I agree, putting a bigger heat sink, maybe, but why waste good electricity on heat, maybe just a super small transformer to just reduce a couple of volts off the regulator. I do not think any part should go over 140 degrees Fahrenheit.

I would check that as it makes the most sense.

Several remarks here : -Rigol means "Laugh Out" in French -Why not watercooling that thing with a bucket full of ice cubes and an aquarium pump ;-) -Why do I give a F... designing my power supplies for proper thermal management if Rigol don't even care... -I think the CEO will be glad about this "million dollar" video !! They now have a price on your head Dave !! -I hope for the head designer that Rigol is not a Chinese company, otherwise he'd be recycled into spring rolls pretty soon !

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)

With the guts hanging out, the LM317 is probably not in the path of the cooling fan.

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.

Don't get why they wouldn't just use a 7805? The extra few cents they could have saved not needing the 2 voltage set resistors could have been put into a decent heatsink.

Yes, I was testing best case. I should have tested worst case.

Yeah, who would have thought. A lousy bridge rectified 5V regulator. Bread and butter stuff.

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)?

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?

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?

40:00 wearing the right shirt for today Dave

Huh. My guess is they tested it only using 120V mains, and that regulator is powered from the main transformer. So you're getting about twice the voltage they had it regulating from, and 5W rather than 1W. Seeing the thin tab, I also wonder if the regulator was replaced with one rated for lower current - say a 300mA one instead of 1A. That would cause it to heat up more easily. Still, with the oscilloscope measurements I expect something is really finicky down in the load also. Not encouraging.

A thought when it comes to possible hardware fixes for the the panel 5V rail: Remove bridge, mount it on standing PCB mounted to the holes. Put a couple of series diodes (say, 2 or 3 of them) on the + side to take down the voltage to the input of the '317, so it doesn't have to work up such a bad sweat (9-ish V instead of 12-ish V). Kludge? Yes. Hack? Yes. But a kludge/hack that can work - I've had to use that trick when designing a simple +- 5 and 12V supply to keep the thermals in check.

Dave... You kick ass! :D

No, you'd get the same 12V.