HELP me choose a lab power supply

[cyberlevi]

Hello,

I am a student looking to get my first (preferably linear) bench power supply for a home electronics lab. I will mostly be repairing consumer electronics, and I might occasionally build some simple projects.

My budget is ~120 euro, and my priority is safety. Some units I am interested in are:

Korad KA3005PS
Stamos S-LS-103

Let me know if I should provide more information. Thank you!

UPDATE: I decided to pull the trigger on the Korad KA3005PS! It won't be in stock until the 5th of February, but I can wait.

[Konkedout]

See if you can confirm that these models use shaft encoder and DAC control instead of a cheap (carbon?) old fashioned potentiometer.  A high quality (cermet or wirewound?) old fashioned potentiometer is OK...

I have never seen your brands but that does not mean much.

I have a couple of cheap Chinese bench supplies.  One of them is a linear and goes up to 50V @ 3A.  My ears tell me that it switches transformer taps as the output voltage is adjusted.  It is good but:
1) Noisy potentiometer.  Sometimes I am able to set the voltage and see it wandering around in my oscilloscope trace.
2) The adjustable current limit will not permit operation in constant current mode.  Rather, the output shuts down when current hits the limit.  Operation in constant current would be useful but I can understand that might lead to overheating in the linear regulator.

The other unit is a switcher which goes up to 30V @ 20A.  Its main problem is switcher noise.  I figured out that this is common mode noise.  I have mostly remedied this with a large hand wound toroidal common mode choke hanging on the front panel.  The core by itself is a few $$ US and I used I think AWG 12 wire used for wiring a house.  I am looking for a photo but I can take a new one if you are interested.

[forrestc]

My experience is that most low-cost bench power supplies are almost identical.   Personally, I'd probably end up with the Korad of the two you suggested, just because they've been around for a while (plus the Amazon reviews for the KA3005P are excellent).

If this is just for powering up devices, pretty much any option should be fine, as the device will have its own internal power supply, which will filter out almost any sins your bench supply produces. But if you're doing precision analog work where power supply noise affects the output, then you might want to be more picky.

As far as direct experience: the only "cheap variable power supply" that I've bought recently is the OWON SPM6103.  It was purchased for a small rework bench where I need a basic DMM and a single power supply.  Haven't used it a lot, but it seems to work fine for the application, which is just powering on a board now and again to make sure I've not created a short during rework and making sure that the on-board power supplies are outputting a couple of voltages.   But... this decision was more about not having much space for a bench DMM and a power supply and wanting something tiny that does both instead of quality.  I don't care about accuracy in this application as the boards have a wide input voltage tolerance and the power supply tests are more "are they there or are they not" than any precision calibration needs.   I also needed 48V output which limits the power supply choices.

Beyond that I can't give you any specific personal recommendations as my "real" bench power supplies are well outside your price range (MX180TP and LHP 60-18).  I only mention these so I can mention that sometimes having multiple outputs are a good thing - I regularly have 2 or 3 channels on these running as I sometimes need to power different parts of the circuit (or multiple devices).  The LHP 60-18 is so I can have a *LOT* of 48V current available and the MX180TP is more of my precision power supply.

[thm_w]

See if you can confirm that these models use shaft encoder and DAC control instead of a cheap (carbon?) old fashioned potentiometer.  A high quality (cermet or wirewound?) old fashioned potentiometer is OK...

They both use encoders.
korad looks to have better current resolution which is nice for low power.

[ataradov]

Go for Korad. It is an excellent power supply and the other one has idiotic layout of the binding posts. 

[Smokey]

You will want more than one channel pretty quickly.  I'm still a DP832 kind of guy. 
I guess you could just buy 3 KA3005PS too.

[Old Printer]

Where you live has a lot to do with it and what the used market is like. In the US many quality vintage supply’s by HP and other quality companies are available at good prices. I have several of the old HP 62XXA series on my bench. Analog readouts, single channel and built like a tank. Service manuals free online. I have Paid anywhere from $50 to $90 each shipped. I also have a few BK Precision 2 channel supplies that were going for under well $100 shipped. Again, very well made with service manuals easily available, but analog readouts. Worth looking into in my opinion. Good hunting!

[ahsrabrifat]

 In terms of safety, both options look good from the given specs. However, Korad KA3005P has a better reputation and better reviews. If budget is not a problem, I think you should buy Korad KA3005P.

[Smokey]

Define what you mean by "safety"....
Safe for you as a human, or safe for whatever widget you have plugged into it?

[cyberlevi]

See if you can confirm that these models use shaft encoder and DAC control instead of a cheap (carbon?) old fashioned potentiometer.  A high quality (cermet or wirewound?) old fashioned potentiometer is OK...
The other unit is a switcher which goes up to 30V @ 20A.  Its main problem is switcher noise.  I figured out that this is common mode noise.  I have mostly remedied this with a large hand wound toroidal common mode choke hanging on the front panel.  The core by itself is a few $$ US and I used I think AWG 12 wire used for wiring a house.  I am looking for a photo but I can take a new one if you are interested.

Both of them use encoders. And I do strongly prefer a linear supply.

As far as direct experience: the only "cheap variable power supply" that I've bought recently is the OWON SPM6103.

There were some OWON models that looked good to me but they were way out of my price range. The cheaper ones I found had mixed reviews.

korad looks to have better current resolution which is nice for low power.

I am heavily leaning towards the Korad. However, the main advantage of the Stamos is that it's from a local store, which means I will probably have easier time with the warranty, in the case I have to use it.

Go for Korad. It is an excellent power supply and the other one has idiotic layout of the binding posts. 

I actually just noticed the weird posts layout on the Stamos.

Where you live has a lot to do with it and what the used market is like. In the US many quality vintage supply’s by HP and other quality companies are available at good prices. I have several of the old HP 62XXA series on my bench. Analog readouts, single channel and built like a tank. Service manuals free online. I have Paid anywhere from $50 to $90 each shipped. I also have a few BK Precision 2 channel supplies that were going for under well $100 shipped. Again, very well made with service manuals easily available, but analog readouts. Worth looking into in my opinion. Good hunting!

Unfortunately, in Bulgaria the second hand market doesn't offer much, and I am forced to buy new.

In terms of safety, both options look good from the given specs. However, Korad KA3005P has a better reputation and better reviews. If budget is not a problem, I think you should buy Korad KA3005P.

I suspect that the Stamos might be made in the exact same factory as the Korad. Not 100% sure though.

Define what you mean by "safety"....
Safe for you as a human, or safe for whatever widget you have plugged into it?

Honestly, I am hoping for both. If only one is possible, I will take human safety any day.

[Aldo22]

I'm pretty sure this is not what you had in mind, but I want to mention it because I now use almost exclusively this device for electronics.
It is a FNIRSI DPS-150.
You need some kind of power source for it. No matter what, a USB PD charger is ideal, but you can also connect a battery pack to the DC input.
It is amazingly accurate and well behaved.
You can see a few measurements in the attachment.
I had my doubts at first, but now I love it.
Well, I might not run my electric cooler 24/7 with it, but for electronics...
I just wanted to say that such a thing exists.

[BillyO]

I'd go with the Korad.  Good products, good company.

I have the Korad KA3305P and long after the warranty expired (4 years after) the com port on the main board got blown out in a lighting storm.  I contacted Korad to inquire about a replacement and they shipped me a new one and charged me only for the shipping.

Service like that is hard to beat.

[BillyO]

It is a FNIRSI DPS-150.

I have one of these but it's still in the box.  What are the noise levels like on it?

[Aldo22]

It is a FNIRSI DPS-150.

I have one of these but it's still in the box.  What are the noise levels like on it?

Hi!
There is some high frequency noise, but nowhere near as bad as with my Longwei PDS-3010G.
Most of it disappears on the oscilloscope if you turn on the 20MHz bandwidth limitation.
Unfortunately, I don't know how to measure HF noise on an oscilloscope in a comparable way.
I can measure ripple to some extent with my scope, but noise? That changes with every setting.
You measure Vpp rather than Vrms, right?

[tooki]

I have the original KA3005P and it’s very nice. The -PS version you linked is even better, with better resolution and a watts display.

I think they’re fantastic value for money, and there’s now years and years of experience with them, proving them to be reliable.

[bborisov567]

I would also recommend the Korad. If you can find some of the Mastech HY3005 clones you can also save some money. The Korad is probably based on the same schematic as them. You can also modify an ATX power supply to be adjustable but the process is far from safe due to dangerous voltages.

[RoGeorge]

I am a student looking to get my first (preferably linear) bench power supply

By their front panel, they are probably the same power supply with a different display.
Enclosure looks small, probably a SMPS power supply, not linear, but I didn't check.

Another option, for a student a DIY linear power supply would be a great project to try. 
Doesn't have to be a DIY 10A power supply.  10A is too much for an electronics lab anyways.  Other things are more important.  For example, would be nice to have a +/- voltage (double) power supply for opamps, or for other circuits that may require two voltages, or another important feature would be to have a big enough radiator, so it can work without a fan.  Fans are usually noisy, and after a while they fail.

Meanwhile, while you finish building your own linear power supply, you can still power other circuits from an USB cable, or from various wall adapters/chargers you may find around.  Or, if you don't want to deal with mains voltage at all, use rechargeable batteries.

I would keep the money to buy other high tech tools that can not be DIY.  Or just wait a little longer until you'll have enough money to buy a linear power supply with 2 or more outputs.  A single output is usually not enough for a home lab.  You'll probably never need 10A at home, but you'll need 2 or more different voltages for sure.

If you look for higher cost lab PSU, there are some models that can also act as both a power supply or an electronic load.

[tooki]

By their front panel, they are probably the same power supply with a different display.
Enclosure looks small, probably a SMPS power supply, not linear, but I didn't check.

My guess is the 10A one is inspired by the Korad, but it’s definitely not the same thing.

The Korad is a 5A linear supply. The 10A is necessarily a SMPS (I don’t think you could fit those specs inside as a linear supply; the Korad is already quite dense), and the serif font used on the controls suggest a very hasty design.

I definitely think one should start with a linear supply, since the last thing a beginner needs is cheap SMPS noise introducing problems they don’t know how to fix.

[BillyO]

You measure Vpp rather than Vrms, right?

It's doesn't really matter if you measure Vrms or Vpp as long as you quote it correctly and keep in mind what potential effect you are measuring the noise for.

Certain noise is very hard to measure with normal probes.  For instance, common mode noise will often show up using regular scope probes.  Normally common mode noise (same on both + and - ) is not going to affect the powered device, but it will radiate noise thought the environment and can be passed on to other connected devices which, if they are ground referenced or sensitive RF equipment, can be adversely affected by that noise.  Differential mode noise may need a differential probe to detect it if there is common mode noise present too.

Also, with a device like this  there may be noise added from the power source.  So to measure the noise it alone creates you'd need a noise free power source such as batteries or a clean linear supply.

[BillyO]

The 10A is necessarily a SMPS (I don’t think you could fit those specs inside as a linear supply

According to this German Amazon ad the Stamos is a linear supply. https://www.amazon.de/-/en/Soldering-Laboratory-Adjustable-S-LS-30-Indicators/dp/B07LBXQC6G?th=1

It also apparently weighs 4.6kg - Is that hefty enough to have a 300VA transformer in it?

My Korad KA3305P has a 375VA transformer in it and I can assure you it weighs a LOT more at 9.1k! 

[RoGeorge]

Same here, my Rigol DP832 has 3 outputs, all summed together giving a total of 195W DC, linear power supply.  Weight is 9.75kg.  Dimensions are 239mm x 157mm x 418mm, much bigger than the proposed PSU models.
https://int.rigol.com/Images/DP800_Datasheet_EN_tcm7-3038.pdf

[tooki]

The 10A is necessarily a SMPS (I don’t think you could fit those specs inside as a linear supply

According to this German Amazon ad the Stamos is a linear supply. https://www.amazon.de/-/en/Soldering-Laboratory-Adjustable-S-LS-30-Indicators/dp/B07LBXQC6G?th=1

That’s a different model which appears to be a rebadged Korad KA3005P.

It also apparently weighs 4.6kg - Is that hefty enough to have a 300VA transformer in it?

My Korad KA3305P has a 375VA transformer in it and I can assure you it weighs a LOT more at 9.1k! 

So those 4.6kg are for the 150W model. A 300W model would thus be a lot more, closer to your KA3305P.

So I think you see why I suspect the 300W Stamos is practically guaranteed to be a switcher!

Edit: I just checked the Stamos’ product listing and it has the manual PDF — and it lists the weight as 2kg. So there is absolutely no doubt it’s a switcher.

[BillyO]

So I think you see why I suspect the 300W Stamos is practically guaranteed to be a switcher!

Yes, I do.

Edit: I just checked the Stamos’ product listing and it has the manual PDF — and it lists the weight as 2kg. So there is absolutely no doubt it’s a switcher.

Good research!

[cyberlevi]

I am the midst of my exam session right now, so my brain is pretty much fried, but I will try to respond to everyone.

The Korad KA3005PS is definitely a linear power supply, and I did email Eleshop to confirm it. The Stamos is listed as a linear power supply, but judging by the weight, yeah, it looks like a switching one.

I did consider getting a Riden module and using a laptop charger with a breakout board to build a power supply that way. But I don't feel all that comfortable with it, and it will cost me about the same. I suppose batteries are an option, but I'd rather just get a regular lab supply. Honestly, I just don't like messing with AC at all, so I'd rather skip building my own power supply for now, even the safer options. My experience is very limited, and is mostly with very low-voltage circuits. I want something that just works for now.

I did consider options like the FNIRSI DPS-150, but I don't really like the controls. Also, I am not sure if it can be safely used for voltage injection.

I already have some tools and equipment for my home lab. It's all affordable stuff, but I think I have most of my potential needs covered.

It looks like everyone agrees that the Korad KA3005PS is a great choice. I will sleep on it, and update my post when I make the decision.

Thank you to everyone who took the time to respond!