For what you need 500mA on that PSU to power USB devices?
If you look at Dave's video you can see there is actually plenty of ripple after the LM317; the ripple seemed to increase with temperature.
Sure, you can stick a larger TO220 and heatsink to the whole thing but any added consumer (like USB) will force the part some more and result in high inefficiency. I would still stick a switched preregulator before the LM317.
The LM317 doesn't have particularly good ripple rejection though, so you've still got the wideband noise problem that a cheap switcher will give.I believe the datasheet says something about 70db rejection and that should be pretty good.
It's not about power consumption nor ripple: the LM317 now takes raw rectified input anyway so a switching preregulator will probably reduce the ripple.
That additional 3-7 watts count towards the thermal characteristic of the entire unit causing the fan to rev a lot of the time and reduce unit life by a few percents. Plus, the bigger heatsink is not free so that money is better spent on something more efficient.
The power supply should not reboot if the USB port is loaded. Like a computer. What do you think of a computer which will crash when a USB port is loaded/overloaded?
For those cellphone chargers: I've also seen measurement devices in the 4-5 digit price sector with USB ports specified for max. 100mA. This was written in the spec. and in the manual. For thumb drives and mice/keyboards this is totally ok. If you need more ports than the typically 1-2 you get, there is always the possibility to use an active usb hub.
It's ok when an USB port limits the current to 100mA. But surely the poor LM317 in the Rigol doesn't withstand additional 100mA.
If I had one of these, then I'd be looking at fitting a discrete linear pre-regulator (any npn TO-220 device with suitable specs) onto the main heatsink, leaving the LM317 as is, but handling less volt drop.
If I had one of these, then I'd be looking at fitting a discrete linear pre-regulator (any npn TO-220 device with suitable specs) onto the main heatsink, leaving the LM317 as is, but handling less volt drop.Then you can just move the LM317 to the main heatsink. Much easier. You will have the isolation issues with both solutions. But it's not really a problem.
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.
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
Yes; it is pretty clear to me! That's my opinion, in your world is there no room for people to have opinions that differ from yours?
I am not attacking you at all - but I call it like I see it, and when I see bullshit, I call it bullshit.
I don't know what you mean "tracking your posts"? I just remember that you and that Citizen guy seemed to have a beef with the supply (and/or Dave) and have been grinding out that beef in the threads on it. You overstate every negative aspect of the unit and downplay every positive aspect to fit your conclusion that it's shit and Agilent is better. You don't even own one of these PSU's and have never used one but you are arguing with folks that own both, and you seemed to get very offended when people criticized Agilent.
One of my other hobbies is racing cars, and the same thing happens on all the car forums. The Mustang guys spend eons arguing with the Corvette guys that their car is better. The Corvette guys argue the same to the Viper guys. The Viper guys argue the same to the Ferrari guys. And the Ferrari guys argue the same to the McLaren guys.
There are some who just appreciate all the cars (or power supplies), and when those folks see someone waging a war against a product, it's pretty clear. As it is in this case. You don't like this PSU - we get it, so don't buy one. But feel free to keep telling us all how it's total shit and only an Agilent is worth buying and every feature the Agilent lacks is unnecessary and every feature the Rigol has is unnecessary
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
Unfortunately once again you don't get it. I don't have any particular love of Agilent as a matter of fact I jokingly rubbed Dave when I said he uses that Agilent meter instead of the Fluke when he's taking certain measurements, why don't you go back and read my original post again.
The point you keep missing is that I am just saying to people to first make sure that anything you buy is a piece of gear that does it's core function precisely and accurately and then look at Ergonomics and build. If that checks out then look at all the bells and whistles because none of the other stuff matters if it's not precise, reliable and comfortable to use.
And BTW I am also into Racing, in this case Rally Car racing. I use to sponsor a rally car and am very familiar with the wars, especially the ones between the Mitsubishi drivers and the Toyota drivers. That's also a good example of this problem because the Mitsubishi EVO 8 & 10 guys keep pointing out how great their Cars are and how much HP they have. The EVO Guys always start out the rally with the best run times but by the third run they always keep blowing up the engines and losing the rally to the Toyota's. (And yes the car I sponsored was a Mitsubishi VIII)
BTW If you think this hobby is expensive try paying $7000 USD for a set of shock absorbers.
105c caps right next to a device that reaches 111c, smells like planned obsolescence (and boiled electrolyte) to me!
Absolutely! I'd consider placing electrolytic caps directly besides a heatsink (>30-40 °C) in a lab grade device a show stopper. It's built to fail.
Meanwhile, i am wondering about something toally different....
Why put in an lm317 where a 7805 would have done ....