bench supply for under $300? - Page 1
Forum section: electronics / beginners

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 26, 2013, 07:18:54 am
content: Hi, I'm looking to get my hands on a bench supply (or possibly build one), but I'm having some difficulties finding one I like...Even though the original Korad broke, I've been kindof using it as a yard-stick... digital screen, load switch, 5A output, etc... Thing is, I can't seem to find anyone that sells it in Canada. Maybe I haven't looked hard enough.There's a couple of supplies I saw on mouser, but one was only 18V/3A, and didn't have a load switch... and the other one was too expensive for my tastes ($310). The expensive one would work, but it also has this sliding 100W scale that I'm not really keen about.I thought about building one from scratch, but I can't find any parts to build my own transformer, and buying a 48V/4.6A AC power brick costs like $150... there's gotta be an cheaper way to build a bench supply...Ideally, my specs are something like 30V/5A, that way I can work on laptops without requiring their OEM power brick. I suppose I could take some ideas from Dave's supply videos, and use some LT3080's and change it to suit my needs, but I'd still need a way to power it.So, can I stick it to the man and build one of these for pretty cheap, or should bite the bullet and buy a pre-made solution?Thanks

author: david77
author_rank: Frequent Contributor
timestamp: January 26, 2013, 08:02:33 am
content: You can get cheap transformers out of old audio power amps. Something like a 2x 100W+ or so amp should contain a nice big transformer. Typically they'll have a split output like 30-0-30V or something similar. In the same amp you'll find at least two huge caps and even heat sinksOr have a look around for a ready made PSU. There are lots of them around for very little money from China. Search this forum for teardowns to find out what's good and what's not.

author: Chalky
author_rank: Regular Contributor
timestamp: January 26, 2013, 08:40:05 am
content: Quote from: justanothercanuck on January 26, 2013, 07:18:54 amYes, I bought the 30V / 5A triple output from BK Precision (via Digikey) for just over NZ$300, which is about US$250 I'd guess.My alternate plan was similar to your, I was going to build one using a $10 second-hand PC power supply, and then adding a circuit to deliver the variable voltage. I still might do that. I have also seen ready made boards that do just that - attach them to a PC power supply and they'll provide you with various voltages, not sure if variable though. Cheers!

author: kripton2035
author_rank: Super Contributor
timestamp: January 26, 2013, 08:58:37 am
content: this one is available to canada as it is "worldwide free shipping" ...http://www.ebay.com/itm/New-30V-5A-ALIMENTATI-DC-Power-Supply-Lab-Grade-Digital-Precision-YH-305D-220V-/200822608788?pt=FR_YO_MaisonJardin_Bricolage_ElectroniqueComposants&hash=item2ec1f5d394

author: mariush
author_rank: Super Contributor
timestamp: January 26, 2013, 06:27:56 pm
content: I've bought a Tenma 2 x 32v @ 3A + 5v @ 2A from Farnell:http://uk.farnell.com/tenma/72-8695/power-supply-2-x-32v-3a-5v-2a/dp/1836057It's about 180$ in my local currency.You can link the two outputs to get a single 64v @ 3A output.The US version of Farnell's,http://newark.com, has the US versions with 110 V input:http://www.newark.com/tenma/72-8695/dc-power-supply-32v-32v-5v/dp/59T9189and they have the 2 x 32v @ 5A version in stock for just a bit over $200:http://www.newark.com/tenma/72-8700/dc-power-supply-110vac-32v-32v/dp/59T9190I've posted pictures with it and the insides here on the forum, imho it's a decent linear power supply, good components and construction inside:https://www.eevblog.com/forum/reviews/tenma-72-8695-2-x-32v-3a-5v-2a-mini-review-teardown/?topicseen

author: robrenz
author_rank: Super Contributor
timestamp: January 26, 2013, 06:45:19 pm
content: I have hadTHISpower supply for about 3 years and it works very well. At $170.00 it is a bargain.It has the very important 10 turn pots on the voltage controls. You can parallel the outputs for 30V at 6A.

author: madires
author_rank: Super Contributor
timestamp: January 26, 2013, 07:14:14 pm
content: Quote from: robrenz on January 26, 2013, 06:45:19 pmYou can't go wrong with a Mastech PSU. Inexpensive, mostly solid and easy to fix (no fancy stuff or parts).

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 28, 2013, 01:43:55 am
content: The supplies I mentioned earlier were theBK 9110and theExtech 382202... I'm sure they're okay supplies, but who knows, maybe my standards are too high.If triosmartcal was in Canada, and the original Korad didn't blow up, I'd probably buy one in a heartbeat. But I didn't know newark delivers to Canada, I'll have to flip through their stuff...Thanks

author: PaulAm
author_rank: Frequent Contributor
timestamp: January 28, 2013, 02:01:06 am
content: If you're looking for cheap; find a dead UPS that uses 2 12V batteries; that will have a nice transformer good for around 28V, then add this:http://www.electronics-lab.com/projects/power/001/index.htmlThere are lots of circuites, that's just one I had handy. And, if you want a digital meter, add this:http://www.electronics-lab.com/projects/test/007/index.html

author: Thor-Arne
author_rank: Unknown
timestamp: January 28, 2013, 10:57:55 am
content: Quote from: PaulAm on January 28, 2013, 02:01:06 amThere's a update to that schematichere.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 28, 2013, 05:15:04 pm
content: Quote from: AcHmed99 on January 28, 2013, 03:57:16 pm$125... wow, that's cheap... Even cheaper than triosmartcal. For that price, I might just buy it for giggles to see if it blows up when I plug it in.I noticed the pictures are for the old revision, and the 240v version, but I asked them and they said it's the 120v version. Looking through the comments seems they don't sell the old revision either, so it's looking very promising...

author: robrenz
author_rank: Super Contributor
timestamp: January 28, 2013, 05:40:51 pm
content: Quote from: justanothercanuck on January 28, 2013, 05:15:04 pmNot cheap when you consider that it is only one output and you are getting three on the $170.00 Mastech. But you are getting more features on the Korad.

author: PaulAm
author_rank: Frequent Contributor
timestamp: January 28, 2013, 07:27:50 pm
content: Quote from: Thor-Arne on January 28, 2013, 10:57:55 amThanks for that update. I had just tagged the circuit for future reference without closely examining it. Now I've added the update to the bookmark. Add the LCD display to that and it looks like a fairly nice PS.

author: nixxon
author_rank: Frequent Contributor
timestamp: January 28, 2013, 08:08:36 pm
content: Quote from: justanothercanuck on January 28, 2013, 05:15:04 pmUS$ 105 incl. shipping here:http://www.amazon.com/KORAD-KA3005P-Programmable-Precision-Adjustable/dp/B0085QLNFM/ref=sr_1_1?ie=UTF8&qid=1359400572&sr=8-1&keywords=KA3005PReviews for the particular item aren't only positive, but the unit seems to hold up.

author: grenert
author_rank: Frequent Contributor
timestamp: January 28, 2013, 08:15:54 pm
content: How about $135 for a triple output? The model number suggests it is a Mastech, but who knows? Disclaimer: I do not have this PS and have no idea if it's any good.http://www.elexp.com/tst_0033.htm#3002

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: January 28, 2013, 08:28:07 pm
content: Quote from: grenert on January 28, 2013, 08:15:54 pmLooks ugly.