# Shopping for a Lab Power Supply

#### ke5nnt

Joined Mar 1, 2009
384
Hey All,

I'm looking to buy a home-lab quality variable voltage/current power supply. I wonder if any of you have any suggestions, and if you could reassure me on one point that I've heard, which is "linear power supplies are better than switching power supplies".

My budget is $150.00USD, a single output is okay but more than that is okay too. Someone else has pointed me to this supply. Thoughts on that one? Thanks all! #### Wendy Joined Mar 24, 2008 22,170 Tanners, AllTex, and BG Micro have a 15V 3A unit for around$70-90. Tanners has a slightly older cheaper model, while the other two are LCD back-lite displays.

The only drawback is the current limited modes will pop LEDs unless you start from dead short. This is because the filter caps create pulse that is powerful enough to blow out the LEDs, but if the caps do not have a charge on them the current setting works.

http://www.vellemanusa.com/products/view/?id=522797

#### PatM

Joined Dec 31, 2010
86
I would check eBay.
There have been some items that I bought that turned out to Not be in good shape, but I bought a Bk Precision 1730 (0-30V, 0-3A) for the ridiculous price of $55. It was in new condition and was sold by a Antenna research company who had used it in their lab. One of the few good deals I made on eBay, but I definitely got a very good deal on that one. Pat - W9ZO https://sites.google.com/site/malfam2/ #### Attachments • 4.4 KB Views: 21 Last edited: #### bountyhunter Joined Sep 7, 2009 2,512 The only drawback is the current limited modes will pop LEDs unless you start from dead short. This is because the filter caps create pulse that is powerful enough to blow out the LEDs, but if the caps do not have a charge on them the current setting works. Actually, it probably means their current limit circuits are not real quick to activate. When starting in dead short it means the current limit circuits are already active and controlling the pass transistor. If you test it with a very low value resistor shorting across the outputs you can probably see a high amlitude curent pulse before it settles on the "set" value of current. This is a common problem and one we handled by sometimes having two current control circuits: one limiter that's fast (but not compensated for stability) and the slower one that takes over and puts out smooth DC current. Thread Starter #### ke5nnt Joined Mar 1, 2009 384 Thank you for the feedback. Further research on the topic of linear vs. switching seems to reveal that switching power supplies may be the way to go. Seems that switching power supplies are far more efficient than linear models, weigh less, generate less heat (part of the efficiency thing) and with increases in MOSFET technology, have become very reliable in noise-free output and longevity. Thoughts? #### thatoneguy Joined Feb 19, 2009 6,359 I have one that is pretty much exactly like the one in your link, but the power button is green. Linear, but very reliable. 3A doesn't get too warm that I've noticed, but does weigh a bit, maybe 2-3 lbs. Outputs are floating, the green center terminal is earth ground, so you can set it up however you like to have it work with a scope. #### bountyhunter Joined Sep 7, 2009 2,512 We had some cheap dual-output linears that had relays that switched between transformer taps as you tunred the voltage up above about 8V. Smaller heatsink, better efficiency. They were good units. #### bountyhunter Joined Sep 7, 2009 2,512 Hey All, I'm looking to buy a home-lab quality variable voltage/current power supply. I wonder if any of you have any suggestions, and if you could reassure me on one point that I've heard, which is "linear power supplies are better than switching power supplies". My budget is$150.00USD, a single output is okay but more than that is okay too.

Someone else has pointed me to this supply. Thoughts on that one?

Thanks all!
Here is a pretty good looking triple output:

http://www.powersupplieswarehouse.com/hy3003f-3-powersupply.html

0-30V@3A (X2) can be configured for 0-30V@6A or 0-60V@3A

#### ke5nnt

Joined Mar 1, 2009
384
Ahh great. Lots of good suggestions/thoughts here. Thanks guys!

#### bountyhunter

Joined Sep 7, 2009
2,512
You will definitely want at least a dual output, best if they can be strapped in parallel to double the current or series to double the voltage. You can also buy two smaller single supplies, they probably won't do the parallel thing.

#### PatM

Joined Dec 31, 2010
86
Thank you for the feedback. Further research on the topic of linear vs. switching seems to reveal that switching power supplies may be the way to go. Seems that switching power supplies are far more efficient than linear models, weigh less, generate less heat (part of the efficiency thing) and with increases in MOSFET technology, have become very reliable in noise-free output and longevity. Thoughts?
I may be wrong, but as noise, switching supplies are never as quiet as a linear one.
I could have saved quite a bit with a switched for my FT-950.
For my use I will always stay away from a switching power supply.
Pat-W9ZO

#### Wendy

Joined Mar 24, 2008
22,170
Side note about the one I referred to, at around 8V you can hear a relay switch. This is to keep the heat down.

It isn't in the picture but there is a large heatsink with a couple of 2N3055's. All three of the vendors I named have other power supplies on their shelves, before making a purchase I would look at them first. The prices are competitive and they are local to us.