Advice on purchasing reliable, general-purpose bench power supply for classroom - Page 1
Forum section: electronics / testgear

author: library1771
author_rank: Newbie
timestamp: September 17, 2025, 11:19:21 pm
content: My classroom started out as the computer lab and has gradually evolved into the school makerspace and repair shop. I keep getting handed random broken equipment without power supplies, or with what ends up being the incorrect one, and I would like to get a bench power supply for testing. I have never owned one of my own, and I've heard good things about the RD60 series, but I know that Rigol is a highly recommended brand as well. I am a tinkerer at heart and so getting an RD6006 or similar has an appeal since I can mess around with firmware and what not. But I also want to be able to rely on my test equipment and I am getting to the point where people are also counting on my lab being up and running for repairs and such. Not just me noodling around with electronics and DIYing power supplies out of buck converters anymore. Do you all have recommendations for a reliable, general purpose power supply that we can use for testing and repairing computers, A/V equipment, and the like?

author: tautech
author_rank: Super Contributor
timestamp: September 17, 2025, 11:37:31 pm
content: Welcome to the forum.Budget ?One thing to look out for if you have multi channel PSU's in your sights is channel isolation, that being all channels are totally independent and without common negatives.

author: Smokey
author_rank: Super Contributor
timestamp: September 17, 2025, 11:48:18 pm
content: dp832.Get the educational discount at TEquipment.Riden is a cheap toy.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 18, 2025, 12:05:35 am
content: Siglent SPD3303X-E and get it on a discount from Saelig.com.

author: Smokey
author_rank: Super Contributor
timestamp: September 18, 2025, 12:50:03 am
content: Quote from: KungFuJosh on September 18, 2025, 12:05:35 am?? The Siglent is more expensive, and doesn't have an actual programmable third channel.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 18, 2025, 01:04:28 am
content: It's also better. So is Saelig.The Rigol interface is terrible. Let's go back to rotary phones while we're at it.

author: library1771
author_rank: Newbie
timestamp: September 18, 2025, 01:06:26 am
content: @tautech I do not have a budget per se since I am submitting this to the school or the PTA for approval based on the fact that it is going to be used to benefit the school at large, and they have historically favored me getting the right tool versus just the cheapest thing that'll do the job. Obviously I want to be responsible with the school's resources though, and I don't want to splash out on something that I won't really use, or on something that is so nice I am afraid to let students use it. But I have never been given a budget for this sort of thing.@KungFuJosh and @Smokey thanks for the recommendations on those sites. I am bookmarking both while I do more research.Would looking at used equipment be worthwhile in the sense of getting more for the same amount of money? I am not sure how quickly power supply tech advances, but it seems like a fairly stable field.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 18, 2025, 01:37:57 am
content: If you can potentially afford a higher budget, look at the series above the SPD3000X, the SPD4000A.The only thing I don't like about the SPD3000X series is that the posts are not the standard 19mm spacing. The SPD4000A is standard spacing, and has some other nice options as well.Tequipment is the only TE company I hate. I've had nothing but bad experiences there. Tequipment tried to rip me off multiple times.Saelig was the exact opposite; I've had nothing but good experiences there. Saelig made sure I was well taken care of even months after the sale. The two companies are nothing alike.

author: J-R
author_rank: Super Contributor
timestamp: September 18, 2025, 03:45:15 am
content: While there is a slight price difference, for this purpose I don't see any good reason to get the DP832 series since the DP932 exists. All three channels on the DP932 are fully isolated, it has a touch screen which speeds up daily tasks (and it's larger), and it has a 100ms ARB function.There was recently some back and forth with regard to the Rigol DP832/DP932 vs. Siglent SPD3303X:https://www.eevblog.com/forum/beginners/psu-buying-again-more-korads-or-a-rigol-dp832/The SPD4323X is quite an upgrade over the SPD3303X. Defpom has some extensive videos of the SPD4306X (same family as the SPD4323X):https://youtu.be/hk8xJ2Xatx4https://youtu.be/25uQlBI0REg

author: Fixpoint
author_rank: Regular Contributor
timestamp: September 18, 2025, 12:31:42 pm
content: I want to mention the R&S NGE103B, which is specifically made for schools and universities. It works very well.

author: paulca
author_rank: Super Contributor
timestamp: September 18, 2025, 12:43:39 pm
content: A big part of the choice and the price is in deciding if you need it to be "always available" or "fixed next day" if not.The cheap end < $1000 it's likely support is a phone number if you are lucky and for repairs its up to you to ship it and pay for it.$1000 and up you start to get manufacturer direct support, further up distributed service centres, further still, collect and swap out repairs, next day replacement etc.If you were to be teaching a course, on the hook from the school for X classes per week, the later might be wiser.If you just want it as "internal lab" equipment and having a student blow a channel on it is not going to impact you greatly, then go cheap.

author: library1771
author_rank: Newbie
timestamp: September 18, 2025, 04:19:00 pm
content: @paulca at this point we are definitely not relying on it for classes, although that might come in the future. So it would be inconvenient if it blew, but not impacting education. And I'd rather have two "cheap" ones than one expensive one since it would let more students access the equipment, but I don't have enough experience to know exactly where the line is between "cheap" and "throw it away".

author: Sorama
author_rank: Frequent Contributor
timestamp: September 18, 2025, 04:33:20 pm
content: Then buy some Korad stuff.2 for the price of 1.

author: KungFuJosh
author_rank: Super Contributor
timestamp: September 18, 2025, 06:16:17 pm
content: Buy 10 of the Korad stuff for what they cost. You could get a bunch of single channel PSUs.

author: nctnico
author_rank: Super Contributor
timestamp: September 18, 2025, 07:34:32 pm
content: Quote from: Sorama on September 18, 2025, 04:33:20 pmI second this suggestion. Something like the Korad KA3005PS.

author: ledtester
author_rank: Super Contributor
timestamp: September 18, 2025, 08:07:04 pm
content: The older linear power supplies are by no means obsolete - especially for hobbyist use. People are still buying and using linear power supplies that were built in the last century. And being simpler they are very servicable.You can get a classic triple-output HY3005/3003 for about $100 on ebay and you'll have two channels which can be put in series or parallel. Some examples:https://www.ebay.com/itm/336166437818https://www.ebay.com/itm/136461464790I would also look on Facebook Marketplace to see what's available - you might be surprised.

author: MathWizard
author_rank: Super Contributor
timestamp: September 19, 2025, 07:30:05 am
content: My main PSU is a Siglent 3303X, and it works great for the low power stuff I do, and I think they have a 3yr warranty, maybe it's more being a PSU.Depending on shipping costs, I'd also say to check ebay. I just got a 1990's era non-digital 3CH PSU from there. There's a lot of similar clones of good designs. And I made my own schematic right away. And all the parts are cheap and easily available, (besides the transformer), and probably already in anyone's parts bin. And none of the circuits are over complicated. So tracking down and fixing the problem should be pretty quick.And as a PSU with just a LM336 as a Vref, it drifts very little (at lower powers anyways) and works great. And has CV-CC modes, Series and parallel modes, and a 3rd 5V channel.

author: paulca
author_rank: Super Contributor
timestamp: September 19, 2025, 08:26:59 am
content: I think the recommendation for the Korads is a good one. I have one in the Tenma brand, 30V, 5A and it's 8 years old, has yellowed a little but works perfectly. Not the quietest but it's still a lot more quiet than a cheap switch more PSU. I only recently replaced it as my primary bench supply last month!They have no thrills or fancy, but they do the job perfectly fine.

author: adam4521
author_rank: Regular Contributor
timestamp: September 19, 2025, 09:49:43 pm
content: I've got a Korad dual output, in the Tenma brand. Also no problems, although the controls that have 5 voltage presets but only 4 recall buttons I find a bit weird (why?).Out of interest I checked out an actual school/physics lab psu:https://www.philipharris.co.uk/product/fe00057619It has a variable AC output, as well as DC. Could be useful for 'curriculum' stuff with lamps and rectifiers. But how do they do it? Do they have an inverter in there as well as SMPS?

author: themadhippy
author_rank: Super Contributor
timestamp: September 19, 2025, 10:24:30 pm
content: Quotedouble check there happy with second hand, going by , all be it limit experience over here, second hand electrical kit is a noQuotecould be variac

author: adam4521
author_rank: Regular Contributor
timestamp: September 20, 2025, 01:26:01 pm
content: QuoteThat doesn't feel likely -- you'd also need two windings to get isolation from mains. The spec is offering 5A shared across the AC and DC outputs, with 0.1V increments on each output...

author: nctnico
author_rank: Super Contributor
timestamp: September 20, 2025, 01:57:03 pm
content: Quote from: adam4521 on September 19, 2025, 09:49:43 pmAC can be generated easely and efficiently using a class-D audio amplifier.

author: Smokey
author_rank: Super Contributor
timestamp: September 20, 2025, 11:00:33 pm
content: Quote from: nctnico on September 20, 2025, 01:57:03 pmThis entirely depends on what the load is. Run a classD amplifier into a resistive load and see what comes out.

author: ledtester
author_rank: Super Contributor
timestamp: September 21, 2025, 01:58:14 am
content: Quote from: adam4521 on September 19, 2025, 09:49:43 pmI don't think this is suitable for the OP. It only goes to 12V and doesn't have a settable current limit.It certainly doesn't appear to be a linear supply. About the quality of the output they don't provide any numbers, only:QuoteThe 5A current limit is also curious. What are they trying to say here?QuoteAre they saying the 5A limit applies to the combined AC and DC current?

author: tooki
author_rank: Super Contributor
timestamp: September 21, 2025, 11:40:17 am
content: Quote from: Smokey on September 20, 2025, 11:00:33 pmWouldn’t that depend entirely on the design of the amp? Yes, in cheap ones we use filterless designs that rely on the inductance of the speaker driver itself, but other designs use full LC filters to output an actual analog wave.Besides, why would you need an AC source for a resistive load? It’s the nonresistive loads where we need AC supplies.

author: temperance
author_rank: Super Contributor
timestamp: September 21, 2025, 12:37:20 pm
content: Maybe you want something like this:https://www.kemo-electronic.de/en/House/Garden/FG025-Pasture-Fence-Device-High-Voltage-Device-for-Electric-Fences.php

author: themadhippy
author_rank: Super Contributor
timestamp: September 21, 2025, 12:45:20 pm
content: Quotein a teaching environment how else do you get to see the difference between AC and DC on diffrent types of loads

author: adam4521
author_rank: Regular Contributor
timestamp: September 21, 2025, 04:23:59 pm
content: Quote from: ledtester on September 21, 2025, 01:58:14 amNo, it's a switcher.QuoteYes, I think the protection limit applies to the combination.For the OP, I agree that adjustable current limit and maybe more than one channel are likely to be more useful for electronics. The spec sheet is certainly vague and hand-wavey in a number of areas. I posted that example because I'd not seen adjustable AC output in a PSU before, and was curious about it.

author: nctnico
author_rank: Super Contributor
timestamp: September 21, 2025, 04:35:52 pm
content: Quote from: adam4521 on September 21, 2025, 04:23:59 pmYup, and if that is your only PSU, it is better to avoid switchers. Switching PSUs tend to push quite a bit of noise out which may hamper doing sensitive measurements.

author: library1771
author_rank: Newbie
timestamp: September 22, 2025, 12:31:56 am
content: Just got an update from the PTC, it looks like my overall budget is between $2,000 and $3,000, split between scopes, PSUs, and digital microscopes.

author: armandine2
author_rank: Frequent Contributor
timestamp: September 22, 2025, 09:04:00 am
content: ...that will focus your purchasing decisions - per student would be better

author: thephil
author_rank: Regular Contributor
timestamp: September 22, 2025, 09:28:23 am
content: There are many very nice PSUs out there – Siglent and Rigol have been mentioned already. I have a Uni-T UDP3305S that I like a lot.But: If you don't need all the bells and whistles like on-device programming, color-display, graphing mode etc., getting a KORAD would be my recommendation (just as some others already said). They are cheap and not bad at all and that will allow you to potentially get more than one and/or have more money for scopes and microscopes.And I second the recommendation not to get a switch-mode supply as your only lab-PSU.

author: paulca
author_rank: Super Contributor
timestamp: September 22, 2025, 10:10:51 am
content: Switch modes have purposes. You can usually find far more powerful PSUs for lesser money if you go switched. The transformer is probably half the value in copper of a good linear supply. That increases dramatically with current.Of course they make circuit analysis with the scope noisy etc. High frequency pulses, etc. etc. So not for delicate or even educational measurements. Nothing worse than trying to work out what noise your circuit is making and what is coming from the PSU. Give your class a signal generator running off a switch mode supply and a scope and you will end up having to explain why there is a big spike and false triggers on the scope.What they are good for is things like battery charging, where 12V, 24V, even 48V with a good few amps, even 10s of amps can come in handy. Probably not many class rooms need to charge kWh sized batteries though.Battery charging and running DC power equipment that wants a few amps. Like laptops.My RDTech 5020 buck PSU and it's Mean Well 48V 10A DC brick find themselves being used to charge car batteries and the like. The Korad has also been used to charge the car battery. 5 amps is enough, ideal even for a slower charge. 100Ah ~ 24 hours.

author: Sorama
author_rank: Frequent Contributor
timestamp: September 22, 2025, 01:15:40 pm
content: Let's not forget the intent of TS.Having a repair shop myself, switched PS would be just fine.You don't even use a classic lab PS for repairing PC's but a working ATX PS, for laptops it may be different)(Although I only have linear PS myself because I am an old m*therf*cker)