Bench power supplies: get what you pay for? - Page 1
Forum section: electronics / beginners

author: be1212
author_rank: Newbie
timestamp: December 09, 2013, 12:26:49 am
content: I need a bench DC power supply. It doesn't need to be programmable. The Mastech HY3005F-3 looks pretty good, but it's a fraction the price of a Tektronix or Agilent supply and that makes me nervous. For example, this line:http://www.tek.com/pws2000-dc-power-supply.Are power supplies something where you get what you pay for? Or, are the low-end Tex & Agilent PSUs just rebranded cheap PSUs? I know that's what happens with cheap scopes.

author: EEVblog
author_rank: Unknown
timestamp: December 09, 2013, 12:33:33 am
content: Quote from: be1212 on December 09, 2013, 12:26:49 amThe Agilent ones are not rebranded. Haven't looked at Tek for years, no idea.

author: be1212
author_rank: Newbie
timestamp: December 09, 2013, 12:53:32 am
content: Quote from: EEVblog on December 09, 2013, 12:33:33 amWould you buy that Mastech, or spend more for an Agilent or Tek?

author: robrenz
author_rank: Super Contributor
timestamp: December 09, 2013, 01:02:46 am
content: What country are you from? You can set it in your personal profile. Practical suggestions need to know where you live.

author: be1212
author_rank: Newbie
timestamp: December 09, 2013, 01:07:22 am
content: Quote from: robrenz on December 09, 2013, 01:02:46 amI'm in the US.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 01:15:11 am
content: Roughly where in the US and how much are you willing to spend? Do you need a bipolar supply? (probably, though I mostly keep even my analog stuff single-supply)

author: be1212
author_rank: Newbie
timestamp: December 09, 2013, 01:28:04 am
content: Quote from: minime72706 on December 09, 2013, 01:15:11 amI'm in Silicon Valley. I'd pay US$500, but would rather pay US$200 for the Mastech if there's no reason to spend more. It doesn't need to be bipolar. It's for simple circuit designs, mainly involving Bluetooth.I've had access to electronics labs in past jobs, but I never thought much about the power supplies we used. They were all top of the line, probably just because money wasn't an issue.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 01:32:09 am
content: Quote from: be1212 on December 09, 2013, 01:28:04 amWould you prefer it be programmable, i.e. digital interface with buttons and rotary encoders, or, more accurately, are you willing to pay for those kind of features?If you just need a single adjustable DC power supply, you can definitely keep the cost far from $500.

author: robrenz
author_rank: Super Contributor
timestamp: December 09, 2013, 01:33:06 am
content: I have had a Mastech HY3003F-3 for several years that works quite well. The only thing wrong was the front panel ground connections were not grounded but the unit itself was grounded properly. I has 10 turn pots for the voltage setting but only one turn for the current setting. Build quality is just ok but it performs very well. I also like the Old Power Designs Precision supplies and the old HP 611X series supplies on Fleabay also.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 01:55:39 am
content: I have a BK Precision 1672 that I got at a slight discount on eBay some years ago and recently picked up a power supply equivalent to the last one ($145) on this page:http://elexp.com/tst_3lk2.htm(It does not look as advertised, which I complained about, but it is functionally equivalent)My main problem with these supplies is the constant-speed cooling fan which is always fairly loud and has no temperature feedback. If I were looking for another power supply (pretend that I am you), I would look for 3 significant decimal points for voltage (and, if possible, current) displays rather than 2. I probably wouldn't care about the extra 5V supply that both of my current power supplies have because the main reason I pay for this kind of thing is for the safety offered by adjustable current limiting.You kind of do get what you pay for, but I have a counter-example. I am fixing some DC power supplies that have been in use at the vocational high school I attended in the first half of the 2000's. They were "Quality Checked" in 1991 and the innards are very low-cost and simple. I saw a bunch of 741 opamps and a 311 comparator - cheap jellybeans.I wasn't fixing electrical problems, I am dealing with the fact that the plastic front panels have become fragile over the years and have cracked or even broken. Yeah, they used cheap plastic, but the very simple circuit implementation is rock solid. Think of the abuse that power supplies would receive in the hands of teenagers.I'm going to do some lookin' to see if I have any personal recommendations.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 02:05:17 am
content: Personally, I would probably buy something inexpensive. I looked athttp://elexp.com/tst_1705.htm, specifically the 1715 and 1735, but since I can't hold it in my hands, I can't tell for sure if you are paying for the brand name. Those supplies may be no better than the one I paid $145 for. One thing I can say about the Vizatek I have is that it has a REALLY impressive torroidal transformer, which is usually a pricey add-on.The BK Precision 1786B looks nice a potentially-nice sort of knock-off of the common HP/Agilent supplies people adore. Again, I can't say much since I can't test it myself.t

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 02:49:04 am
content: I'm using Electronix Express as my sole source because anything else I can think of is unwieldy to deal with. They're also located in NJ, which is near where I live.My final opinion for the night is this:I think you'll fail to regret it if you get a triple-output power supply (more like dual-output since I would ignore the fixed 5V output) and I would recommend something like:http://www.elexp.com/tst_0033.htmIt's not very pretty, but I'm sure the quality is just fine compared to other sub-$200 power supplies. All of the power supplies I mention here are going to be heavy as hell, so don't let the physical size turn you off.If you're sure that you just want a single-output DC power supply, I'd recommend something like the 6003L-1 here:http://www.elexp.com/tst_03l1.htmThe one that I own is probably worth buying over the one above simply because it has a button that switches the output on and off:http://www.elexp.com/tst_3lk2.htmI opted for the 60V/3A version, personally.I have not spent much time using the $145 Vizatek dual-output power supply (mentioned just above), but I was impressed with the torroidal transformer and, as a plus, whenever you turn it on for the first time after applying power, both the voltage and current displays flash the number of the beast. (6.66V 6.66A)Good luck.

author: RickieSalad
author_rank: Regular Contributor
timestamp: December 09, 2013, 11:37:55 am
content: I have the Mastech and it's worked just fine for what I've needed it for. My only real complaint so far is the voltage adjustment. There isn't a way to "lock" in the voltage you select. The pot works fine but it's a 1 turn pot so moving it a small amount can make a relatively big change in voltage.I keep having visions that I'm going to quickly reach across the bench for something and just perfectly bump the knob and go from 3.3v to 20+ and have lots of magic smoke coming out all over the place. It's not a huge problem considering it is such a cheap supply and I've resorted to taping the knob in place as a little "just in case" insurance. Just something I thought I'd mention.

author: BeerCannon
author_rank: Contributor
timestamp: December 09, 2013, 01:34:26 pm
content: I have the Vizatek PSM3003LK2, purchased from Electronix Express. It's been a solid, reliable unit. I can't say much more than that since it's my first benchtop power supply and I'm by no means an expert. I like it because it has a 1A 5V fixed output as well as a 3A 30V max variable output, and they're both on the front of the unit. Paid $119 US for it.http://www.elexp.com/tst_3lk2.htmI've found this under other brand names as well (Austek, Wellzion) , with the slightly modified model number "MPS 3003LK-2".

author: BeerCannon
author_rank: Contributor
timestamp: December 09, 2013, 01:49:40 pm
content: My only complaint with the Vizatek MPS-3003LK-2 is this: there's a button to toggle the power to the variable output on and off. There's a corresponding LED that indicates when the load is "on". When you switch the load off, the voltage and current displays go to zero. This makes sense, it reflects that the output is off.. but it would be nice if the voltage display showed the present voltage setting even when the load is off. That way, you could dial up the voltage you want BEFORE appying power to the load. After all, there IS a separate LED indicator for the load.As it stands, when working on a new circuit I usually disconnect any circuit from the Vizatek, turn the 'load' switch on, dial up the voltage I want, turn the load switch 'off', connect my circuit, then turn the load switch 'on' again.The unit DOES retain the last voltage setting, so you can turn it off and back on knowing that the same voltage will be selected.

author: SLJ
author_rank: Frequent Contributor
timestamp: December 09, 2013, 02:10:31 pm
content: If you do get a Mastech make sure you test it thoroughly. The QC on them is poor. Someone here just found the + output on their Mastech was grounded due to poor design and a case screw hitting the + rail on the circuit board.bench-supply-ground

author: BravoV
author_rank: Super Contributor
timestamp: December 09, 2013, 02:18:01 pm
content: Quote from: be1212 on December 09, 2013, 01:07:22 amQuote from: be1212 on December 09, 2013, 01:28:04 amWith this above 2 facts alone, if I were you, pretty confident will not have this kind of problem, you should contact Vincent (FreeElectron) on where to find "elite" grade used bench PSU.

author: Rigby
author_rank: Super Contributor
timestamp: December 09, 2013, 02:25:35 pm
content: Quote from: SLJ on December 09, 2013, 02:10:31 pmTest any power supply thoroughly.

author: minime72706
author_rank: Frequent Contributor
timestamp: December 09, 2013, 04:25:26 pm
content: Quote from: BeerCannon on December 09, 2013, 01:49:40 pmAgreed - this does piss me off.

author: Rigby
author_rank: Super Contributor
timestamp: December 09, 2013, 04:56:08 pm
content: Here's a video where a friendly Scotsman mods his power supply to show him the set current & voltage at the press of a button, whether or not the load is connected.It probably won't be this easy for any power supply, but hopefully it fires some neurons among those of you that dislike the behavior he's subverting.

author: mazurov
author_rank: Frequent Contributor
timestamp: December 09, 2013, 10:21:46 pm
content: I have Mastech HY3003D-3 which works quite well. The only issue is current limiting circuit in it is kind of slow. I also have HY1803D ( the model liked by tattoo artists for its reliability ) which also works well. I got it for free since it had its 2N3055 shorted internally.I also have Agilent E3640A. This is the one I prefer using - little things like settings save/recall and accurate voltage/current make big difference.