Need a Bench variable power supply? - Page 1
Forum section: electronics / beginners

author: ronyd
author_rank: Newbie
timestamp: October 07, 2022, 12:36:46 pm
content: Looking to purchase new or used variable 0-30vdc power supply for my electronic drumming projects.Seems like any sold Amazon (mostly chinese makers) < $140 or so all have the same issues with fine voltage and current adjustments, and/or just not reliable after months of use. And the reviews vary for the same supply. Who says it's great and other not so. Just don't trust the reviews.Is there any supplies out there < $100 that are reliable and have good control over adjustments to voltage and current?Or do i just have to bite the bullet and spend $300+.

author: Grandchuck
author_rank: Super Contributor
timestamp: October 07, 2022, 01:09:08 pm
content: Older, used supplies are usually more repairable. If you have the skills and the wherewithal, a used unit could be your best option.If so, try to find one that was made by a notable company and one that information is available for.

author: ronyd
author_rank: Newbie
timestamp: October 07, 2022, 01:21:08 pm
content: yeah i hear ya.I bought a Tektronic oscope used in perfect condition for $200 with a function generator.

author: MikeK
author_rank: Super Contributor
timestamp: October 07, 2022, 01:44:46 pm
content: Lots of satisfied users of the Korad supply. They had issues early on, but it has gone through several revisions. It's linear, not switch-mode, and hard to beat for the price.

author: mag_therm
author_rank: Frequent Contributor
timestamp: October 07, 2022, 01:49:12 pm
content: Hewlett Packard made a range of similar, linear power supplies from 1960's to 1980's.I have two of HP 6253A each rated 2 * 24 V 3 A from BMI Surplus. Some resto was needed when I got them about 12 years ago.They are old, large, heavy, inefficient, but reliable in my experience. I & V reg both go down to zero. and with coarse/fine trim pots.And the dual supplies work well either in series or parallel.

author: radiolistener
author_rank: Super Contributor
timestamp: October 07, 2022, 02:13:40 pm
content: KORAD KA3005D, it provides up to 31 V / 5.1 Amp

author: MikeK
author_rank: Super Contributor
timestamp: October 07, 2022, 03:46:34 pm
content: You should be able to get this very cheap:https://www.ebay.com/itm/254871206331Yes, his asking price is overblown, and I've already told him so. He now knows that a similar new one is about $90 on Amazon. If you point out "Hey, this seems to be the same as the Mastech supply...I could give you $20 for it", you could probably get it.* I think he's getting a lot of his stuff for free or very cheap and he looks up prices but doesn't really know what things are worth. If you're interested...Pick a price, let me know, and I'll offer him less so that your offer is more attractive. I don't need yet another bench supply (unless it's a fancy precision one). By the way, I've already bought other things from him (two multimeters) so he is legit.* A better approach might be to first mention that the *NEW* Mastech HY3003D is *MUCH* cheaper. When he asks if you're interested in it you could say that what you'd be willing to offer is much less. Then, if he bites on that, offer your lowball.Mike

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 07, 2022, 04:46:01 pm
content: So if you buy the cheapest stuff you can find you get crapped on, and internet reviews are not reliable.What else is new.

author: MarkF
author_rank: Super Contributor
timestamp: October 07, 2022, 05:27:24 pm
content: I like these little low powerHewlett Packard HP 6216A Variable DC Power Supplies.Although this one is over priced. I usually was able to get them for $50 with shipping included.

author: austfox
author_rank: Regular Contributor
timestamp: October 07, 2022, 10:18:38 pm
content: You could always build your own. Silicon Chip has just published a 30V 2A design in their current issue:https://www.siliconchip.com.au/Issue/2022/October/30V+2A+Bench+Supply%2C+Part+1

author: Gyro
author_rank: Super Contributor
timestamp: October 07, 2022, 10:28:18 pm
content: That one looks like an LM317 with external current boost transistor. Maybe not an ideal starting point (but should work if the current limit can be made reliable).

author: Excavatoree
author_rank: Frequent Contributor
timestamp: October 07, 2022, 11:20:11 pm
content: I have one of these, and it's a good supply, if you only need 1.5 amperes. The pots are 10 turns, and it performs well. I'll admit that I paid 40 dollars (edit: each) for two or three of these at my surplus dealer, years ago, and thought it was a good deal.https://www.ebay.com/itm/361975454012?hash=item54476b193c:g:QtEAAOSwZKBZEimW&amdata=enc%3AAQAHAAAAoM769xSakKFhlE4HkvVoqal4qqXAjrEzOy9KYqSaYB%2FzSQx3sdD3%2Bx4oqkqSQ60BiQ3rh1RxM5DMzZaELwowaZb5Uwoh3gmz121YYI31NJ5L408HQEZUlB%2FTnWBlZTpvryga8xEAptAxW687PXlDoW7iQiq2Ec%2BHvR7zpVy%2Foc%2BwKWYQb6EcDahPf3LhYzQnoNAA391KnlnMCoy0mapXSDU%3D%7Ctkp%3ABk9SR6z17cv2YA

author: brucehoult
author_rank: Super Contributor
timestamp: October 08, 2022, 01:37:55 am
content: Dumb question, and I'm looking at buying my first adjustable voltage and current power supply myself ... but why do you (or I) need 30 V?Virtually everything I do is 3.3 or 5 V. I can see needing 12 V occasionally. But 30 ??I've been using Apple / Samsung / RPi 4 USB 5V power supplies which generally can give all the current I need, but not enough to let out magic smoke. The Samsung and Pi 4 ones are 15W/3A, Apple is 18W or 20W. They're all pretty cheap if I blow up a power supply :-) And decent quality as far as I can tell.But I'm thinking about dropping some money on a bench supply that can limit the current to less, and not itself get blown up.I'm tending towards this Jaycar labelled one at the moment. Dave didn't hate one of its ancestors a few years ago:https://www.jaycar.co.nz/0-to-30vdc-0-to-5a-regulated-power-supply/p/MP3840

author: MarkF
author_rank: Super Contributor
timestamp: October 08, 2022, 02:33:43 am
content: Quote from: brucehoult on October 08, 2022, 01:37:55 amIf you're going to drop that kind of money, consider the Siglent SPD1305X (30V/5A) or the SPD1168X (16V/8A).

author: ledtester
author_rank: Super Contributor
timestamp: October 08, 2022, 02:42:17 am
content: Quote from: brucehoult on October 08, 2022, 01:37:55 amfwiw, it looks like it is also sold as a "Tekpower TP3005T":https://www.amazon.com/Tekpower-TP3005T-Variable-Linear-Alligator/dp/B00ZBCLJSY/

author: brucehoult
author_rank: Super Contributor
timestamp: October 08, 2022, 02:49:02 am
content: Quote from: MarkF on October 08, 2022, 02:33:43 amUS$265 plus tax plus shipping from overseas?The Jaycar I pointed to is US$125 plus tax, available off the shelf in my provincial New Zealand city.

author: brucehoult
author_rank: Super Contributor
timestamp: October 08, 2022, 02:53:02 am
content: Quote from: ledtester on October 08, 2022, 02:42:17 amYup. Looks the same. Looks cheaper at US$80, but Amazon says shipping is $53.22, making it just as expensive as I can get it off the shelf in a retail store in my provincial NZ city. Plus that would come with a US plug and from the specs 110 V only power needs not 240 V.

author: bdunham7
author_rank: Super Contributor
timestamp: October 08, 2022, 03:28:06 am
content: Quote from: ronyd on October 07, 2022, 12:36:46 pmHow much current do you need? Older linear supplies from BK Precision, HP, Tektronix, Power Designs and so on work pretty well and are repairable. Many of them are reverse polarity and backfeed protected so they won't blow up as easily as many modern versions. A dual-channel 20 or 24V supply can be used in a series configuration if you need the full 30V (or more).

author: Doctorandus_P
author_rank: Super Contributor
timestamp: October 08, 2022, 04:25:07 am
content: I quite agree with Bruceholt and others here.30V3A has been a "standard" for 30+ years but electronics has changed a lot in that time span.I'd much rather have a few small but relative accurate and noise free power supplies than a 30V 3A one.The smaller power supplies such as 15V 1A can get 90% of the jobs done, and for the other 10% the 30V 3A often is also under powered.But of course this also depends a lot on the sort of projects you are interested in.Quite a shame the L200 has gotten out of fashion. It is (was) a 5-legged LM317 with some extra circuitry for current limiting. And by amplifying the voltage over the shunt resistor, it was very easy to make an adjustable current limit with it.

author: Peacefool
author_rank: Newbie
timestamp: October 08, 2022, 04:58:58 am
content: You have a nice Tek oscilloscope... I'd get a good old HP36xx lab power supply to go with it. Most are CV/CC linear power supplies, w/10 turn pots that blow away the load/line regulation and ripple & noise characteristics of any modern SMPS crap out there, and they're silent too (i.e. no fan) --see attached specs. I have two HP3616A and they've been solid like a rock. For modest current requirements you may want to check out this one now:www.ebay.com/itm/255751227479(I have no connection to the seller)

author: MarkF
author_rank: Super Contributor
timestamp: October 08, 2022, 11:59:17 am
content: Quote from: brucehoult on October 08, 2022, 02:49:02 amThe Jaycar link you pointed to lists it for $259. That's all the further I looked.Nowhere did you say you could get it for 1/2 price!

author: brucehoult
author_rank: Super Contributor
timestamp: October 08, 2022, 12:04:19 pm
content: Quote from: MarkF on October 08, 2022, 11:59:17 amjaycar.co.NZNZD is worth 0.56 USD at the moment. Also NZ advertised prices include 15% sales tax while US one's don't. Also, it's in a retail store local to me, so no freight or import duties etc.

author: MarkF
author_rank: Super Contributor
timestamp: October 08, 2022, 12:21:56 pm
content: Quote from: brucehoult on October 08, 2022, 12:04:19 pmARE YOU REALLY GOING TO ARGUE THIS!!!YES!JAYCAR.CO.NZ

author: brucehoult
author_rank: Super Contributor
timestamp: October 08, 2022, 12:27:42 pm
content: Very good. You can screenshot.NZ web sites have prices in NZD, and include 15% tax. NZ$259 incl tax is NZ$225 pre-tax which is US$126.42 at this second.

author: rdl
author_rank: Super Contributor
timestamp: October 08, 2022, 03:06:20 pm
content: I have a couple of the E3610 power supplies and a couple of these:The CPS250 (in various color schemes) and the very similar BK Precision 1651 show up frequently on eBay for around $100 and are pretty much all a beginner needs. User manual and service manual are available.If you go for an HP 36xx try for a later model (three colors binding posts) or Agilent branding as any little problems will have been fixed.

author: MathWizard
author_rank: Super Contributor
timestamp: October 08, 2022, 05:42:09 pm
content: For cheap China types I think the KORAD KA3005D mentioned above is consider decent enough.Yeah if you don't ever want over 12V, then it would usually be better to get one rated near that.There's ton's of real basic/low part supplies that might just use a LM317 on a little heatsink/ I would not trust any of them for more than a few Watts of power.My 1st variable "PSU" was just a 12V SMPS feed into a LM317 circuit. It was ok for a few transistors on a breadboard.

author: John B
author_rank: Frequent Contributor
timestamp: October 09, 2022, 12:46:42 am
content: So what exactly is the deal with Korad nowadays? It is sold under a few names like Tenma and Multicomp Pro, also comes in 30V or 60V, 3A or 5A variants.What revisions have been done, is there a voltage spike at turn-on etc ?I would consider them to be equivalent with the quality of gear Jaycar sells, but not over priced like basically everything at Jaycar.