Lab Power supply - Page 1
Forum section: electronics / beginners

author: Deni258
author_rank: Newbie
timestamp: January 19, 2014, 12:08:59 pm
content: Hi,I wanna buy linear, maybe dual lab power supply. I don't want do anything with sound, so it doesn't have to be extra low noise. CC, CV would be nice. I think 15-20V and 3-5 A will be enough. Can you recommend me some with price under 200$.Sorry for my bad english.Jirka

author: Rigby
author_rank: Super Contributor
timestamp: January 20, 2014, 07:48:37 pm
content: Yeah, a couple ofthese Korad PSUswould probably work well for you. Slightly over your budget, but they're really capable supplies from what I've heard. All the issues that they suffered upon release have been remedied.

author: Deni258
author_rank: Newbie
timestamp: January 20, 2014, 08:12:10 pm
content: I was looking on this one ... and i like it, but how do i avoid buying those with issues? I saw videos by Dave and i don't want to end up with any bad one

author: electronics man
author_rank: Frequent Contributor
timestamp: January 20, 2014, 08:24:25 pm
content: Why don't you make one?? that's what I'm doing

author: IvoS
author_rank: Frequent Contributor
timestamp: January 20, 2014, 08:35:04 pm
content: http://dum.bazos.cz/inzerat/31168227/Laboratorni-regulovany-zdroj-30V-5A--WEP-PS-305D-LED.php

author: Rigby
author_rank: Super Contributor
timestamp: January 20, 2014, 09:53:26 pm
content: Quote from: Deni258 on January 20, 2014, 08:12:10 pmYou won't. The factory has replaced/fixed the issues for every supply it makes. If you get one made within the previous 1.5 years, you'll have the fixed up version. Just don't buy from a dodgy place.

author: tony3d
author_rank: Frequent Contributor
timestamp: January 21, 2014, 05:57:28 am
content: I bought a Korad, and have been very pleased with it. It has performed flawlessly for me now for the past five months. Not one issue. I have ran it as long as 8 hours straight drawing 2amps, with no issues. I like the read outs, and the very compact size. Just make sure you order a good set of leads for it. I bought several from Frankie, and couldn't be happier. I bought the Korad from SRA Solder, and I can tell you they are excellent to deal with. Great customer service! My image below shows the cheap leads that came with the unit.

author: icon
author_rank: Regular Contributor
timestamp: January 21, 2014, 03:54:54 pm
content: HiCan these Korad PS be bought in the UK? I've had a look but I can't see a supplier? Or a clone of it?ThanksJohn

author: Monkeh
author_rank: Super Contributor
timestamp: January 21, 2014, 04:06:34 pm
content: Quote from: icon on January 21, 2014, 03:54:54 pmhttp://uk.farnell.com/tenma/72-10480/psu-bench-single-3a-30v/dp/2251946

author: icon
author_rank: Regular Contributor
timestamp: January 21, 2014, 04:13:39 pm
content: Wow £53! - oh, awaiting delivery. Drat. Still - having one of those!ThanksJohn

author: Maxlor
author_rank: Frequent Contributor
timestamp: January 21, 2014, 04:34:28 pm
content: Careful with the rebadges. I bought a Velleman unit (PS3005D, which is actually a Korad KA3005P (i.e., has the serial and USB ports. Korad's -D models don't have them)). While the hardware issues are no longer present (the boards are like the fixed revision that were shown in the videos), the firmware has a couple of issues, at least some of which seem to be fixed with the non-rebranded Korads (I might be wrong, it's just the impression I got watching videos):It has 5 storage positions (M1-M5), whereas the up to date Korads have 4. The 5th storage position is accessed by Pressing M4, then turning the wheel clockwise. The kicker is: it always switches to M5 if you turn the wheel, even if you wait after pressing M4, or the key panel is locked! At least the output is switched off whenever the storage position is changed.It has no LED for the lock.OVP doesn't work. The procedure described in the manual for setting the voltage limit does nothing.OCP kinda works: it's not a separate limit, instead it means that if you hit the set current limit, the output is switched off instead of the PSU going into CC mode. I'm getting the impression that there is no real limit though that would save you in case the PSU partially failed.Even if beeps are switched off, it still beeps whenever you press the OCP button. And the beeps are loud and sound horrible.I've thought about modifying the firmware, but all writing on the chips has been filed off, and I can't be bothered to identify the chips. Maybe someone else can provide some info?Btw, overall I'm still happy with the power supply. It has quirks, but it works, it's quite small and the fan is quiet while using low currents. The displayed voltage reads 0.02V high in the single-digit V range that I use most. If you've set a low current limit (< 1A), there is a bit of overshoot when switching on the output, probably because the supply goes into CC mode during ramp-up (the CC LED flashes briefly). If you set it at 1.5A, there is no overshoot. (I only tested it with small loads around 1W however.)If you do get one, buy the newest revision (recognizable by the lower right LED being labelled "LOCK" instead of "M5".)

author: tony3d
author_rank: Frequent Contributor
timestamp: January 21, 2014, 05:23:42 pm
content: Actually the OVP works just fine. Once you set the voltage, then press the OVP it will trip the output off only if something in the circuit cause voltage to exceed the voltage you set, not by adjusting the voltage higher on the Korad. That just reset the threshold to a higher setting. Works perfect on this end as does the OCP.

author: Maxlor
author_rank: Frequent Contributor
timestamp: January 21, 2014, 06:13:31 pm
content: You're right. I went back and tested the OVP by connecting an old AA battery to the PSU. Setting the PSU to 0.95V or lower and connecting the battery would trigger OVP, setting it to 0.96V or higher would not trigger it. Indicated voltage with the battery connected was 1.27V.I was also able to sometimes trigger the OVP simply by connecting (short circuiting) and unconnecting the two leads, probably because of overshoot.