Recommendations for a basic (0-30vdc, 5(ish) amp) Bench PSU - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: November 12, 2017, 05:12:21 am
content: I want to get Dad a new power supply to replace the crap cheapy one he has (that died) for Christmas.Can anyone make any recommendations, new or second hand? He was looking at one ofJaycar MP3840, but both Dave (in his early days) and Clive Mitchell have done videos on cheapy power supplies (even ones that catch fire) so I'd rather spend the money on a decent second-hand unit than a new crap unit, but don't really know where to start (in terms of brands/models).Just needs to be in that "entry level" price point, I don't really want to be spending $1000 on a power supply.

author: tautech
author_rank: Super Contributor
timestamp: November 12, 2017, 06:24:35 am
content: If he'd be happy with a pretty solid little SMPS then MCH K305D.Bit of my experience with them and later in the thread some small problems we've had and schematics for them a buddy had found.https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/

author: nctnico
author_rank: Super Contributor
timestamp: November 12, 2017, 11:07:58 am
content: I have an MCH K305D but I can't say I'm really pleased with it. Sure it is small but it also produces a lot of switching noise on the output and it needed re-doing the mains wiring to make it somewhat safe (which I wouldn't call a small problem).

author: DTJ
author_rank: Super Contributor
timestamp: November 12, 2017, 11:14:23 am
content: I'm happy with my MCH K305D.I opened it up to check it was safe, while there I installed a toggle switch as an output on/off control.Maybe not for low noise applications but it works fine for my needs. Good value for ~AU$80

author: TMM
author_rank: Frequent Contributor
timestamp: November 12, 2017, 11:50:51 am
content: Probably best to avoid switchmode unless you need small size/weight or high output current.I have the old Jaycar MP3087 (dual tracking version of the single channel MP3086 one Dave reviewed eons ago) and the only faults I have found with it are that it can overshoot on power up, lacks a soft output on/off button and is a rats nest of wiring inside. To avoid the overshoot I just remember to unplug one of the leads from each channel when powering it off, and hotplug banana leads to turn circuits on/off instead of power cycling the whole supply. Other than that, I can't fault it. I don't know that I'd pay $350 again for one but it is certainly a big step above the $60 30V/5A linear single channel jobs on ebay. I think the current offerings at Jaycar are of a similar calibre to the Jaycar one I bought 5 years ago.A friend bought this Tenma dual supply and seems pretty happy with it. I don't think it is tracking though - probably just two independent supplies in one housing. It's a Korad supply rebranded with element14's Tenma house brand. The Korads had some issues with a dodgy batch (or underspeced, I forget) of transistors blowing up years ago but I think this is sorted out by now.http://au.element14.com/tenma/72-10495/power-supply-2ch-30v-5a-adjustable/dp/2251947The single channel version has less attractive pricing:http://au.element14.com/tenma/72-2540/power-supply-1ch-30v-5a-prog/dp/2445412It seems they are phasing it out in favour of this supply from possibly a different OEM, which immediately has a problem (blue LED displays...)http://au.element14.com/tenma/72-2690/bench-power-supply-1-ch-30v-5a/dp/2563982Speaking of those $60 ebay ones, I have two of the chinese "PS-305D" from ebay (example:http://www.ebay.com.au/itm/LINEAR-DC-POWER-SUPPLY-0-30V-0-5ADC-OUTPUT-PS305D/350487052418?hash=item519aa80082:m:mRmSmv03fFee-MyBbdqajIQ) and I would definitely avoid them unless you are planning on re-engineering it to suit your needs. One of mine had a fault out of the box because the transformer had a bad secondary connection so at certain output voltages it would constantly hunt between a working and non-working tap on the transformer. Upon further inspection the transformer has aluminium secondary windings and they had just twist and taped the lead wires since aluminium doesn't easily solder. After fixing that I investigated further and found that they were dropping an excessive voltage across the (single) pass transistor. Likely the transformers that fell off the back of the truck that week did not have secondary voltages which matched the tap changing voltages that are implemented by the control circuitry. At certain output voltages you could dissipate more than 75W in the pass transistor at 5A. The transistor is rated at 100W but who knows if chinesium transistor meets spec and with only a metal plate as the heatsink I have no doubt that after some time it would become very hot and reach secondary breakdown. I fixed that problem by changing the transistor to one from a reputable manufacturer and reverse engineering their tap-changing circuitry to change the thresholds, so it only switches in a higher voltage tap when there is less than 3V dropped across the pass transistor. With those mods I'd trust it to 3A continuous... while keeping an eye out for magic smoke. In it's unmodified form I'd probably only trust it for 1.5A continuous, and 5A for a very shot amount of time (1minute)...

author: ez24
author_rank: Super Contributor
timestamp: November 12, 2017, 06:04:59 pm
content: If you can find one of these. Cool retro look and well respected by the forum. One in good condition would make a nice gift.https://www.ebay.com/itm/Precision-2020B-DC-Source-Power-Supply-0-20V-0-2A/222615046464?hash=item33d4e40940:g:qyMAAOSwNnRZlDki

author: NiHaoMike
author_rank: Super Contributor
timestamp: November 12, 2017, 10:34:56 pm
content: Check for updates on the PSU that blew up. The issue has been identified (bad placement of output capacitor) and will reportedly be fixed.

author: nctnico
author_rank: Super Contributor
timestamp: November 12, 2017, 10:42:29 pm
content: For general purpose use I'd look for something old-school linear with a transformer and 10 turn pots.

author: rstofer
author_rank: Super Contributor
timestamp: November 13, 2017, 12:54:45 am
content: I think I would avoid any SMPSs. The noise is a serious issue and filtering just adds parts to the project.You might want to reconsider the 5A requirement if you find that 3A linear supplies are easier to get. Most of my projects require less than 100 mA and 1A is a real big deal. True, that's my projects, but are you certain of the 5A requirement?Here's an HP supply which I assume was a credible supply at some point in history. Note that neither output will go anywhere near 1A much less 3A or 5A. I have to assume they sold some...https://www.ebay.com/itm/Hewlett-Packard-6205B-Dual-DC-Power-Supply-0-to-20V-0-6A-0-to-40V-0-3A/322844574522I don't know anything about these supplies and I'm certainly not recommending it but at some point in history, the output was adequate for something.http://literature.cdn.keysight.com/litweb/pdf/06205-90002.pdfI think these desired higher output currents drive the decision toward an SMPS and I'm not sure that is a good idea for a lab supply.Obviously, opinions vary...

author: PCChazter
author_rank: Contributor
timestamp: November 13, 2017, 07:19:03 am
content: I have one of these, and find it works great. Not a terrible cost either.http://www.volteq.com/volteq-regulated-variable-dc-power-supply-hy3005d-30v-5a.htmlSent from my LG-M703 using Tapatalk