I want a decent bench top power supply help please - Page 1
Forum section: electronics / beginners

author: taco
author_rank: Contributor
timestamp: January 06, 2015, 06:26:57 am
content: Hello,I saw a RSR hy3002-3 power supply, but I was wondering if someone could tell me some good kit ones that will last or a decent one for sale. I would rather spend a little more for one tharpt will last verses getting half of what I should look for to grow into.Thanks

author: JoeO
author_rank: Frequent Contributor
timestamp: January 06, 2015, 02:40:01 pm
content: What are you planning on doing with it?What voltages are you looking for? At what current?

author: rdl
author_rank: Super Contributor
timestamp: January 06, 2015, 03:53:06 pm
content: Look at the Korad KA3005P. If I was buying a new, basic bench power supply today, that's what I'd get.http://sra-solder.com/korad-ka3005p-programmable-precision-variable-adjustable-30v-5a-dc-linear-power-supply-digital-regulated-lab-grade/Another more basic unit is this one:http://www.mpja.com/0-18VDC-0-3-A-Variable-Benchtop-Power-Supply/productinfo/29600%20PS/

author: DrMag
author_rank: Regular Contributor
timestamp: January 06, 2015, 04:11:49 pm
content: You suggested kit ones; I own the first of these two, and it's lasted me a number of years. The second also looks promising.http://www.elexp.com/ProductDetails.aspx?item_no=01PS3040K&CatId=2d6558c8-938e-4373-927d-951d70d0a048http://www.amazon.com/Elenco-Triple-Output-Power-Supply/dp/B0002DT0GU

author: taco
author_rank: Contributor
timestamp: January 06, 2015, 11:25:06 pm
content: Thanks for the help. The Korad unit looks like what I'm looking for. I am just trying to begin to set up a work area for learning electronics. I have been able to half *** things enough to repair video games (everything from poker machines to slots) and decided maybe it's time to really start learning what I'm doing. i just got my first real multimeter (Fluke 87V) instead of my toasted harbor freight special. The power supply I was using was a converted ATX power supply.One question I have is that the model K3005P is the programmable model. What are the advantages of programmable vs the K3005D ?Thanks all

author: george graves
author_rank: Super Contributor
timestamp: January 07, 2015, 12:25:12 am
content: The P has a USB port, so you can control it via PC. It can be handy. And the price difference is usually just $10.The Korad is built down to a price - but it a very good first power supply. I have 2 of them. Surprisingly accurate. The fan sounds like crap (I plan on replacing it), and the "beep" sounds sickly.The mpja units can't store values, or allow you to set an exact value with a few button presses. You'll constantly driving yourself crazy trying to dial in a voltage. And the pots wear out, and then control of the thing is frustrating.

author: AG6QR
author_rank: Frequent Contributor
timestamp: January 07, 2015, 12:33:42 am
content: Quote from: DrMag on January 06, 2015, 04:11:49 pmI own the second one of those, the Elenco XP720. It is a reasonable value, does what it claims, with a solid, well constructed enclosure and heat sink, and an excellent instruction manual that's downloadable on the web. But it lacks a few features that are really useful in a bench power supply. It has no adjustable current limit or constant current mode. Its adjustable voltage rails won't go below 1.25V (it's a LM317/LM337 based standard design almost straight off the data sheet). It has no metering, neither voltage nor current.I bought mine as a cheap second supply, for when I want a couple more rails. The pos/neg rails are especially nice for op-amp prototyping. I upgraded mine by replacing the stock pots with 10-turn ones. It's fine for what it is, and the price is attractive, but I'm glad I have a different supply on my bench with adjustable current limiting and constant current mode.I'd recommend it only to those who understand and accept its limitations. It does what it says it'll do, but it doesn't do everything a good general purpose bench supply ought to do, IMO.Quote from: taco on January 06, 2015, 11:25:06 pmI don't own either Korad model, so I hope someone else chimes in on this point. But my understanding is that the programmable model can be controlled by a computer, while the non-programmable model requires you to push buttons and twirl knobs on the front panel to control it. The programmability might be useful for certain types of automated testing, or maybe for automated timed battery charging. If the computer you use to control the supply also has some sort of sensors, you could write code to adjust output voltage or current based on what your sensors are telling you, with all sorts of possibilities. Some will find that very useful, others not so much.

author: rdl
author_rank: Super Contributor
timestamp: January 07, 2015, 12:37:53 am
content: I only posted the link to the P model because it was the one Dave reviewed (which blew up). Don't worry, they fixed the problem.I think the average hobbyist type user could live without the remote PC control. It doesn't add much to the cost though, so it may be worth it if that sounds like it might be useful to you either now or later. I would assume it requires and may only work with Korad software, but I don't know for sure.Yeah, the MPJA power supply is pretty basic, but it's decent and inexpensive. The Korad is a ridiculously good value.

author: nixfu
author_rank: Unknown
timestamp: January 07, 2015, 12:45:52 am
content: I think that old used HP programmables are kick ass for the price you can get them for because there are so many surplus these days.I have a HP 6632 myself. I have several power supplies on the bench and its my favorite and my go-to.http://www.ebay.com/itm/HP-6632A-System-DC-Power-Supply-0-20VDC-0-5A-100W-HPIB-Programmable-Opt-20-/361175272786?pt=LH_DefaultDomain_0&hash=item5417b94d52

author: CrashBang
author_rank: Contributor
timestamp: January 07, 2015, 02:51:35 pm
content: Or you can be really braveand build your own. Check out the tutorials from:Martin Lortonhttps://www.youtube.com/user/mjlortonPeter Oakeshttps://www.youtube.com/user/TheBreadboardca

author: nanofrog
author_rank: Super Contributor
timestamp: January 07, 2015, 09:50:07 pm
content: You'd do a lot better to purchase a quality used unit. Far better built, and tend to be quiet. Can usually be repaired as well, should it get damaged (manuals tend to include schematics, which can usually be downloaded for free).Here's a few examples of triple output units under $100 to your door.BK Precision 1651Lambda LPT-7202-FMPower Designs TP340All of the above units offer both constant voltage and constant current operation, which is definitely preferable in a bench supply.*fixed TP340 link

author: rdl
author_rank: Super Contributor
timestamp: January 08, 2015, 12:30:45 am
content: I have one of those BK 1651 power supplies. Tektronix also sold it as the CPS250.www.ebay.com/itm/Tektronix-CPS250-triple-output-power-supply-/301468316138It's not a bad power supply at all. As a matter of fact, of the three used power supplies I've bought off eBay, it's the only one that works 100% correctly. Personally I would never recommend something used from eBay for someone looking for a "decent" power supply, but maybe I just have bad luck.

author: nanofrog
author_rank: Super Contributor
timestamp: January 08, 2015, 09:36:29 am
content: Quote from: rdl on January 08, 2015, 12:30:45 amSuspect there's a better chance of getting it for less with the BK label on it in general though, not just with these two listings.Quote from: rdl on January 08, 2015, 12:30:45 amIn general, I've had good luck with used gear. More issues with used hand tools than T&M equipment actually.Obviously your mileage did vary, but I stand by the value aspect for used bench PSU's. Buyers do have to be careful of course (as with anything), and I tried to locate what appear to be decent units, not just blindly link by price (each listing has return policies, sellers that seem to know a little something about what they're selling, and good feedback w/ enough of it to be confident).For those linked, the Power Designs I think would be the "safest bet" (load tested by seller, 30 day warranty & return policy, seller specializes in T&M equipment w/ 100% feedback).

author: george graves
author_rank: Super Contributor
timestamp: January 08, 2015, 09:54:24 am
content: Quote from: nixfu on January 07, 2015, 12:45:52 amI love old test gear - but when you are starting out in electronics, there is a learning curve that some people don't get over.My opinion is that you buy, rather then build (or repair) - it gives you the best chance of success. Some day when you're awesome, you can become Dave, and repair thing on the fly.

author: GreyWoolfe
author_rank: Unknown
timestamp: January 08, 2015, 01:04:09 pm
content: Quote from: DrMag on January 06, 2015, 04:11:49 pmI also bought the Elenco kit. I did the pot swap, added bleeder resistors and over/reverse voltage protection. It was fun to build/modify and, as an added bonus, I did a presentation at my ham club on linear power supplies and included the build process of the kit as bonus material. The club enjoyed the presentation.Just as a note, it is not my only power supply, I have 2 others.

author: drakke
author_rank: Regular Contributor
timestamp: March 22, 2015, 01:06:44 am
content: Quote from: GreyWoolfe on January 08, 2015, 01:04:09 pmWhere did you find the information to perform these modifications?

author: cellularmitosis
author_rank: Unknown
timestamp: March 22, 2015, 05:57:05 am
content: Quote from: rdl on January 06, 2015, 03:53:06 pmI bought the 2 Amp version of that supply, and after hacking some cheap 10-turn pots into it, I'm actually pretty pleased with it. I use it whenever I need single-digit milliamp resolution.https://www.eevblog.com/forum/testgear/picked-up-a-csi1802x-bench-supply-($50-0-18v-0-2a)/A project I have planned is to buy another one and replace the pots with a small board which uses DACs to allow remote control of the supply from a PC over USB, or perhaps creating a board which will drive the supply with a signal generator, etc.One of the advantages of buying a dirt cheap supply is that their simpler designs are easier to hack on, and if you screw it up, you haven't blown a large investment.

author: GreyWoolfe
author_rank: Unknown
timestamp: March 22, 2015, 12:42:27 pm
content: Quote from: drakke on March 22, 2015, 01:06:44 amThere is information all over the internet. Just type Elenco 720 modifications. You can also google bleeder resistors and over/reverse voltage protection. I upgraded the caps to Panasonic also. I had the resistors and diodes on hand and had some of the cap values. The biggest cost of upgrades were the 10 turn pots and knobs. I got creative with the bleeder resistors for the adjustable voltages. the resistors fit in the pad hole with the capacitors so they reside underneath the caps with the caps raised just enough not to touch. For the larger cap on the fixed 5 volt, I soldered the resistor to the bottom side of the pcb. At some point I may do the N5ESE meter modification, I haven't decided yet.