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.

Awesome, I love hearing that!

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.

:) 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.

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).

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.

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.

I watch every video all the way through, & love 'em! keep up the great work :)

Great rant Dave.

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...

Fantastic rant Dave

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

Oh, yeah, didn't notice, thanks!

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 =)

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

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

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

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.

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

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

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????

Dave you rock!Amazing catch!

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

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.

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.

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.

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

Connect it to a pan and boil water!

Summary : Rigol tried to get away by running a STMicro LM317 Pass transistor at ridiculously high 5W the transistor junction getting hot much over the part maximum operating temperature. As per Steve's word, nobody in their right mind (with integrity) would design this. This is not a mistake it's a sweep it under the rug and sell it strategy. This regulator powers the digital section and is next to supply bypass cap that will dry up because of the excessive heat, all DP832 will fail in the field. How could this even get pass a design review meeting. This is a huge design oversight, Steve believes they had to know it and sweep it under the rug by running the fan loud all the time but the supply will still overheat and reset itself. Note to Dave : Even my 1985 Marshall tube guitar amplifier which has a digital DSP section is using a 5V tap on the power transformer to supply the digital section, none of this cheap rigol cutting corners with a bypass transistor dissipating 5W to scale the voltage down to 5V ! Rigol must do a recall and fix ALL the units they sold. As for me i will avoid this brand once you know they do these cheap tricks somewhere they will do other one across their products.

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.

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

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?

Love the rant btw! :)

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?

What about voltage ripple from switching regulator? Is is going to be OK in this precise device?

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

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

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.

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

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

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

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

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.

I would check that as it makes the most sense.

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.

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

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.

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.

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

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?

how about a lower voltage tap on the transformer?

Silly question, but cant you just drop in a more efficient DC to DC convertor that doesnt generate as much heat?

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.

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?

You know what? I think it was designed that way on purpose, so it will fail and most people, and specially big companies using this, will just buy another one. Designed obsolescence. You see it in the computer world all the time (that's my background), power supplies with obviously underspeced CAPS, super high speed HD's with little to no heat sinking (I'm looking at you HP and your 2.5" SAS drives), and the list goes on...

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.

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.

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)

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

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 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?

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

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.

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%.

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.

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

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

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 ;)

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 :)

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!

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

Thanks Dave. I'm considering the DP832A and am wondering whether this issue is present or has been fixed.

Is it likely Rigol will address the lm317 issue?

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.

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.

Does that mean that higher end model that shares the hardware also has this issue?

Before that was the Korad blowing up!

The (incorrect) assumption is that the overheating LM317 is causing the 5V digital supply voltage to drop below some threshold and this caused the DP832 processor to reset. I have been able to replicate this exact scenario with my DP832A after upgrading to the latest 1.14 firmware version. Replacing the LM317 with a switching regulator does not fix the reset issue and neither does using an external 5V supply. Yes, I know the LM317 is getting quite hot, but this is not the cause of the resets - sorry Dave ;-) Unplugging the flat ribbon cable from the top power board cause the software to report an error with the analog interface, but reboots also stops completely. The problem seems to be related to the firmware version coupled with an (as yet unknown) issue between the main control board and the top power board. The processor either detects an out of range condition while monitoring the analog board and resets (unlikely) or the comms between the two boards stalls and a watchdog kicks in, causing the main processor to restart. This is most likely a protection mechanism to prevent serious damage to the PSU or attached equipment. I bought my DP832A some time ago from the South African Rigol agent (now bankrupt), so I don't think Rigol is going to replace it for me. Shipping the unit back from South Africa is also not practical, so my only option is to fix this bugger. Has anyone managed to solve this issue on their own?

Oh dear god that's horrific.

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)

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?

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

Why did they use LM317 ???

will they still exchange yours because you voided the warranty by opening it?

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.

What if this was made on purpose? Just to break down couple of months after warranty ends?

Even after you took the beast apart?

It passed the Cost Accountants Review Hearing, the hell with the engineers, (smile)

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.

Let's get a bigger radiator and problem solved ? Yes but there is still more power dissipating on regulator than is needed for all front panel electronics 0,7 *5 = 3,5 W compared to 5 W they have to waste in that circuit. Very efficient solution Congratulations RIGOL...

Was the supply design in a country with a 110v ?