Decent bench PSU ? Quality/ used or cheap/new from China ? - Page 1
Forum section: electronics / testgear

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 22, 2019, 03:46:57 am
content: I have most parts to make a reasonable linear or SMPS bench PSU, but getting proper transformers, buttons/display, knobs/case/etc, is the real holdup. So it's about time I get a nice bench PSU for hobby use. So I guess 0-30V, 10A or so should be fine. I'd like more than 1 channel.On ebay I can find lots of good brandname, but older, PSU's. They cost a lot, after shipping/etc, working or non-working.Or I could get a cheap SMPS from China, a lot of them would be fine for me, but I'd rather ^^, if I can afford it. And I'd rather have a linear supply, for less noise, and easier to fix. I rather not go over $200US.

author: tautech
author_rank: Super Contributor
timestamp: February 22, 2019, 04:29:04 am
content: 10A is a big ask for most bench PSU's and probably only available in SMPS and then you will have some switching noise for sure.If you set your sights a little lower @ 5A there are many more choices, even the linear duals that can be paralleled will give you 6A.

author: bitseeker
author_rank: Super Contributor
timestamp: February 22, 2019, 04:39:32 am
content: Yep, you can have linear, high current, low price — just not all three at the same time.Determine how much voltage, current, and (lack of) noise you actually require, before you go shopping. Many of the older bench supplies will be 200W or less (often 100W or less), so they'll either have high voltage and low current (e.g., 40V and an amp or two), or vice versa (10V or less and several amps).You can get something like theHP 6632A/B(20V, 5A) for around $100-200. It's not small and might need a quieter fan installed, but can also act as an electronic load. There are service manuals and schematics online, too.

author: tautech
author_rank: Super Contributor
timestamp: February 22, 2019, 05:56:17 am
content: If you can't stretch for a multi-channel unit consider a couple of MCH K305D.Here's a thread on them:https://www.eevblog.com/forum/testgear/cheap-variable-switching-power-supply/They did make a 3010D but I couldn't vouch for their reliability.If you want something decent and new, the 3ch SDP3303X-E have been popular and can be hacked to the better X model.

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 22, 2019, 06:29:19 am
content: Hmm, I forgot again how expensive this stuff gets. The used HP is in range, too bad the connections are on the back. I could save for a new SPD model, they look real nice for my hobby needs. I still have to make my own LM723 PSU tho, those old circuits are making a lot more sense to me now.There's not near as many used PSU's on ebay as I remembered, not like bench DMMs or scopes. Most are only single channel as-well.There's no rush, I could save and get nice new 1 this spring, rather than cheap out on a cheap China model. I bet 1 of those SPD3303X-E or something in that price range, would last me a lot longer than 'computer gaming tech' that I spend a ton of money, always upgrading.

author: beanflying
author_rank: Super Contributor
timestamp: February 22, 2019, 06:53:30 am
content: Don't be put off by the stock rear terminals on the 6632B range have a good read of the entire threadhttps://www.eevblog.com/forum/testgear/agilent-66332a-dynamic-dc-source-20v5a-repair-and-mods/msg2077351/#msg2077351If you are trying to operate on a tight budget a re purposed PC power supply will get you +-12V rails like my hack job here. A bit of ripple like most switchmode supplies but a reasonable add on to one good quality low noise supply. The little 3A switchmode box makes this $10-20 well spent.

author: tautech
author_rank: Super Contributor
timestamp: February 22, 2019, 06:53:53 am
content: Wack K305D into eBay, Amazon or Aliexpress, they don't cost very much, only ~USD50.Just use some additional bulk capacitance in your projects and they make for a good little cheap PSU.Smart fan and I can't blow mine up. You can't series or parallel them though.Mine does a lot of battery charging duties but is still used on the bench when I need something quick.

author: ebastler
author_rank: Super Contributor
timestamp: February 22, 2019, 07:28:52 am
content: Quote from: tautech on February 22, 2019, 05:56:17 amThanks tautech, I had not come across the "hacking" option. The X model offers better resolution in setting the current and voltages, right? (Any other differences?) Does the hack involve just a firmware change?Edit: Found it here,https://www.eevblog.com/forum/testgear/siglent-ads-firmware-file-format/msg1830584/#msg1830584While we are at this, could you clarify the difference between the SDP3303X-E and the Siglent SPD3303C? The price difference is quite significant, at least over here. It seems that the color screen and the refreshed cosmetics are the only technical difference? (And probably the C version can't be "upraded" to the better resolution?)Thank you!

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 22, 2019, 07:30:15 am
content: Yeah whatever a typical supply does is fine, but the more range the better for general purpose I guess.I already have some salvaged and DIY PSUs, so I want to step up a few levels.Tautech u have me very interested in the Sigilent, and/or that price range. It's 3 channel, hooks to PC. I'd regret only having a single channel. And something like that will look great next to a Siglent SDS1104/1204, getting 1 of them too.Aw and so Siglent is from China as-well, they are the upper-end for my needs and still cheaper than a lot of used top-end 80s/90s models on ebay. I mix them up with Agilent/Keysight.

author: tautech
author_rank: Super Contributor
timestamp: February 22, 2019, 08:03:29 am
content: Quote from: ebastler on February 22, 2019, 07:28:52 amNewer and better product mostly but some nice touches like the actual load in V, A and Watts. The website still doesn't show the updated display but it looks just like the new single channel PSU's:https://www.siglenteu.com/power-supplies/spd1000x-series-programmable-dc-power-supply/Like this: (SPD3303X-E)The factory webpage shows the later FW version X/X-E display:http://www.siglent.com/ENs/pdxx.aspx?id=1132&T=2&tid=17Decent TFT display too and you can do stuff like this with them:https://www.eevblog.com/forum/testgear/this-graph-brings-tears-to-my-eye/

author: bitseeker
author_rank: Super Contributor
timestamp: February 22, 2019, 05:36:19 pm
content: Quote from: beanflying on February 22, 2019, 06:53:30 amExactly.lordvader88,The panel on many of these system power supplies have the cutouts in the alumin(i)um for front connectors. You just have to wire it up and use a knife to make openings in the vinyl/plastic overlay that covers the holes in the panel.Anyway, there are a lot of possibilities out there. If you can wait and save up to budget for a fancier supply to get you what you want or need, go for it.

author: akis
author_rank: Frequent Contributor
timestamp: February 22, 2019, 05:50:29 pm
content: Are you not interested to build your own?I have made two.One is a dual channel, huge torroidal (300W ?) and is linear with pass transistors with a huge heatsink and fans (3 fans) with auto-temperature control. I have also fitted it with a third probe to sense thevoltage drops on the leads. After I made it I realised it should have a fourth probe to sense the voltage drop better. It can do about 30V at 5A or 2 x 30V at 3.5A more or less.I also made another dual channel, linear PSU but this has a preceding stage with an LM2679 and a feedback loop to bring the input voltage down and allow the last linear stage to run much cooler.I think making a bench PSU is fun. More advanced hobbyists can use an Arduino to control voltages and currents and provide a display etc. Unfortunately when I was making my PSUs I did not know about the Arduinos.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 23, 2019, 04:05:52 am
content: Words of advice, personal experience here, buy good brands Lambda, hp, rigol, sorensen, xantrex, kikusui, kepco, any reliable and proven brand, avoid cheap china based smpsThey will fail lack of sturdyness and reliability, and mostly bad design ..... they can't withstand full power very long, trust me i know and i saw a few blow quite spectacularly lollMy company bought many Mastech smps based psus hy3010 dual rail, bad soldering, bad design and the list goes on. They failed at 90% quantity.I bought an old Kikusui pad supply and it is another story, rock solid in every way and hold maximum power for long uses.In process of buying another one with more power ..I have 2x 640va toroidals xformers with each 4x 30vac 4 amps outputs sitting duck, recovered from an power amplifier, and 4 beautiful very long heatsinks for to-3 transistors.It take times / money and good design to have an reliable psu ... lots of google schematics to choose from ..But I the end, i simply choose existing models based on ac phase controlled power supply (Xantrex Sorensen, Kikusui ..) they dissipate only the required power, not like an standard linear model ...The only smps brand i know to be reliable and very well protected againat shorts, overheat etc ... are Meanwell, done lots of test with them and they are worth to buy in every way, i saw many fake chineese clone of them.my 2 cents

author: tautech
author_rank: Super Contributor
timestamp: February 23, 2019, 04:39:11 am
content: Quote from: coromonadalix on February 23, 2019, 04:05:52 amYour 2c doesn't mention the usage of tapped secondaries, a standard principle in design of well built PSU's to minimize unnecessary power and heat dissipation.

author: Tomorokoshi
author_rank: Super Contributor
timestamp: February 23, 2019, 04:55:01 am
content: That first supply is hard to decide on. It's too easy to get stuck looking for the one perfect supply. That's what TEA is for. You will need more than one! It's like deciding on the one screwdriver to buy. By definition different screwdrivers are needed.Anyway, consolidating questions brought up in this fairly regular topic:1. Low power delicate, or high power bulk loads?2. Precise current limiting, or ballpark current limiting?3. Fast current limiting, or slow current limiting?4. Banana plugs spaced at 3/4" apart? Note: many cheap supplies are at some random distance.5. Digital or analog readout? How precise?6. How many channels? Can they be in parallel? In series? Tracking?7. External programming? Analog? Digital?8. Linear, switcher, etc.?9. How electrically quiet?10. How audibly quiet?11. Repairable? Schematics available? Some repair parts available? User community?It may be that you get one supply for 50% of your work, another for 30%, another for 10%...

author: lordvader88
author_rank: Frequent Contributor
timestamp: February 25, 2019, 09:53:58 am
content: @ akis - I have put together little simple PSU's, but I want some better than anything I'd make, both electrically and physically, and overall still cheaper.I will make some PCB's with LM723 and SG3525A-D, I own those chips already. I look forward to playing with them more and learning a bunch more. The biggest hold up on that has been lack of correct transformers, money for quality parts, and I'm learning more week by week.There's no rush tho, the basic PSU's I made, are good enough so far what I've tried. Very soon I'll make another, but much better LM723 model.

author: coromonadalix
author_rank: Super Contributor
timestamp: February 25, 2019, 06:19:08 pm
content: Quote from: tautech on February 23, 2019, 04:39:11 amHave you seen this application in many linear brandsome mastech and clones does etc... but you dont know it until you open it or have any schematics.Smps ones doesnt use this topology, if i want to build one myself ill use tap secondaries relays ... many want cheap price vs functionalityIf the op wants power and reliability for any cheap or expensive projects, he / she will go with reliable and proven brands.When the op will suply a project and a cheap psu will fail, i hope it wont cost a fortuneThe last mastech hy3010 smps i used, was outputing 16 volts at 1 amp, a mere 16 watts and it blown spectacularly ... the op will decide whats best ... and learn in some case (s) as i did ?

author: coromonadalix
author_rank: Super Contributor
timestamp: February 25, 2019, 06:23:53 pm
content: Quote from: Tomorokoshi on February 23, 2019, 04:55:01 amThats a very good list

author: akis
author_rank: Frequent Contributor
timestamp: February 26, 2019, 10:15:29 am
content: I would add : voltage sense on load, which needs another 2 leads to the load, unless anyone knows another way.

author: tautech
author_rank: Super Contributor
timestamp: February 26, 2019, 10:25:30 am
content: Quote from: akis on February 26, 2019, 10:15:29 amYep, that's optimum and adds a few $ to the price of new units too.Siglents new single channel PSU's have front sense terminals, SPD1168X and SPD1305X and with 1mV/mA resolution.Defpom had a look at the 1168X here and he will look at the 1305X soon.