Electronics      Reviews & Guides

Introduction


In the quest for a low-noise, low-cost DC power supply, I happened upon this one. 

We'll see if it's any good.



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In This Article


Some Specs

Description & Basic Use

Components and Design

First, The Bad

Now, The Good

Powering Hobby Electronics

Phone Charger Output

RF Power Detector

Voltage Spikes?

Conclusion




Some Specs

AC output:  No
DC output:  Yes
Current indicator:  Analog meter, numbered in 0.2 Amp increments
Current limiter?   Yes  (alarm / shutoff somewhere above 1 amp)
Current output (max):  1 ampere (nominal)
Maximum voltage:  about 15.4 to 15.5 volts DC
Polarity:  Single  (0 and + voltage only)]
Recovery Time:  less than or equal to 100 ┬Ás
Ripple Noise:  less than or equal to 1 millivolt RMS
Short-circuit protection:  Yes
Temperature Coefficient:  less than or equal to 300 ppm/degree C
Type:  Linear
Voltage input:  110/120 volts AC or 220/240 volts AC (back of unit is marked to distinguish them)
Voltage output:  0-15 volts DC in 0.1 volt increments
Weight:  4.3 pounds (about 2 kg)




Description & Basic Use


This power supply goes by different brand names.  W.E.P., Yescom, Yihua, Flexzion, and probably others.  Quite often it will have the model number PS-1501s, or something like that.

This power supply has a metal housing and good-quality knobs, switches, and connectors. 

I used to have a multi-hundred-dollar Hewlett-Packard power supply, and it wasn't even as nice as this. 

The PS-1501S is built around a 2N3055 power transistor.  As you may know, these tend to get hot.  They put it on the outside of the back of the case, with no heatsink.   That's actually not unusual for a 3055-driven power supply, although it would have been nice to see a heatsink.

This is a linear supply, so it will get hot no matter what the output voltage.  That said, it should get hotter with longer periods of use.

In half-hour bouts of use, though, I did not find the transistor to get all that hot. 

It's conceivable you could burn your hand on the power transistor, so be careful.  According to the instructions, "It is better enough space for heat dissipation, long time used high-power tube chassis rear of a high temperature, do not hand touch." 

Ya got that?!

There is no convenient way I can see to attach a heatsink without modding the case.  As I said, it's probably not necessary anyway. 

This power supply doubles as a voltmeter.  There are two red terminals and a common "ground" or "negative" terminal, which is black.   Switch between the two functions (power supply or voltmeter) with a metal toggle switch in the front of the panel. 

Components and Design


Mostly there are standard components throughout:  resistors, caps, diodes, transistors.  However, there's also an 8-bit CMOS microcontroller chip in there;  socketed DIP, so it's easy to replace if for some reason you had to.  This chip is part of the LED display controller, it looks like.



The transformer is labeled as to what color should have what voltage.  Helpful.  It's also easy to get to. 

The power on/off switch is a small rocker switch with a "1" and "0", as you would expect for a piece of equipment like this.


Next, let's talk about the good and bad aspects of this power supply.


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Table of Contents







First, The Bad


The paper folding are have instruction of useless.  Informations detail are thinly.





Now, The Good


Despite the very brief, somewhat confusing instructions, the power supply is very good.

In fact it's the best one I've seen at this price point, ever. 

You probably couldn't build a power supply this nice from the parts without spending more money.  This is the mighty manufacturing power of China, and it seems they have gotten very good at what they do.  I think there's been a big improvement in Chinese electronic goods over the past decade.

Is it perfect?  Again, refer to the price.  If we don't expect a $200 power supply in a $40 item, it becomes possible to have great enjoyment from it. 

The voltage output is fairly accurate.  Out of the box, it varied by no more than 0.05 volt, relative to what my GE voltmeter said.   In one or two places, it was off by as much as 0.1 volt.  However, in most basic applications, this will not be an issue. 

If your work demands very precise voltage, you might want to check the output with a very accurate voltmeter and adjust the output knob until you get exactly the voltage you want.   The adjustment precision is just a tad finer than the LCD numbers show you, for what that's worth.  I suppose you could put a multi-turn potentiometer on here to get finer adjustment, if you really wanted.

The unit includes a couple different types of test leads.  There are wire-hook leads for connecting around thin wires and component leads.  Handy! 

The metal housing is painted blue, with a yellow front panel.  It is a nice color scheme for electronics, better than the infinite shades of dull gray and dirty off-white that I've seen for most power supplies.

The voltage-indicator LED display is big and easy to read.  It's like the numbers from a 1970's calculator or clock radio.  As it should be.


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Table of Contents



Powering Hobby Electronics



Can you power an electronics project with this power supply? 

Yes, if the project is single-polarity.  This unit worked brilliantly for powering a small, solid-state amplifier which was made with all the grounds tied to a common ground plane.

To power a project device, you'll need the correct DC power connector with wires, so that you can run them to the outputs of the PS-1501s.   Make sure you get the polarity right if you solder up a power connector. 


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There was no audio noise that I could notice in the amp output.   It sounded as clean as if I'd used a battery.  I don't know that this will be the case for every device you'd use, but at least you know the potential is there.  (Oh, that was a pun.  Darn it.)   See also "Noise", below.

For projects that require dual polarity, the PS-1501S power supply would not work.

There are still tons of projects you could build with single polarity.   There are even ways to build op-amp circuits to take single polarity (star grounding, for example.  Or, perhaps this method.)

Bottom line:  almost any project that can take battery power can use the PS-1501S instead of a battery.  The only other requirement is that it has to draw one ampere or less, and the voltage has to be about 15V or less.  There again, that's quite a large number of circuit projects!



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Table of Contents



Noise


This is a linear power supply, which is inherently lower-noise than a switching-mode power supply.    This supply should work well for small-signal audio, such as pre-amps.  A phono pre-amp typically uses no more than a few hundred milliamps, even if based on a vacuum tube such as a 12AX7. 

The noise seems to be around 10 mV  Update:  Nope... less than 1 mV;  I just checked it with better equipment.  I read 0.5 to 0.7 mV.  The published specs were correct.

Even 10 mV would be pretty good for this class of power supply, and I'd say very good for a unit this cheap.   In contrast, a decent switching-mode power supply would be more like 50 mV... however, I'm finding they can measure as low as single-digit millivolts.

Someone will probably point out that cheap electronics can have some sketchy quality-control, and they'd be right.  Obviously, this is a low-cost power supply, though.  Could you get one with 20mV of noise, like one person did?  I guess it's possible.  But this unit uses an old-fashioned 2N3055, so it shouldn't have the ragged electrical noise you'd get from a switching power supply.  Read this article and scroll down to "Spectrum Analysis".  This is the power supply that I used.  I also use it to power a radio amplifier that I built.  No problems whatsoever. 

QC can vary with these types of things.  They might not all be made by the same factory.  My test unit happens to work great.  If for some reason you get a unit that's not as good, it shouldn't be too hard to resolder components or swap them out for better ones, as long as you know what you're doing.

The basic design is capable of less than 1 mV AC noise, from what I've tested.

    



Phone Charger Output


Although many readers will employ this unit as an all-around hobby power supply, it actually was designed for testing and repairing wireless phones.  As such, there is a USB 5-volt power output jack.  You can use this to charge your phone, of course. 

Nowadays there are other devices that use USB chargers or power sources, too, so it's definitely a handy feature.

The USB power output works independent of the other outputs.  It will still work while you're using the power supply in "voltmeter" mode.  That's important, because you'd need to power the phone while testing voltages with the test leads. 



RF Power Meter

The instructions give no indication as to how to operate the RF power meter.  There's only an extremely vague hint about RF being detectable when the phone powers up. 

I haven't really tried to test that aspect of this device (will update later, maybe).  You'd have to use the test leads, probably while the 5-volt USB power is connected to the phone.  I say that because nothing happens when you power up a phone near the supply.  So, the coupling doesn't seem to be inductive (although that would have been pretty easy to do, I'd think.)


              



Voltage Spikes?


None.  I checked using a couple different methods;  my copy of this unit did not produce voltage spikes at turn-on or shut-off.  While it could also depend on what's connected to the power supply, so far no problem.

There's a 0.1 uF ceramic disc capacitor from the DC GND terminal to the transformer casing.  Looks like they're shorting inductive transients to mains ground.  Inductive ringing is usually in the MHz or at least the high kHz range.

I've used this supply to power gadgets made with fragile semiconductors.  Nothing has gotten fried.

With any of these power supplies, test them.  You might get one from a different factory.  There are a lot of variables that are tough to predict:  wire length, bends, etc.  These can affect inductance, which means they can affect inductive ringing. 


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Table of Contents



Conclusion


It's a low-cost power supply, so you should test for inductive transients, etc., before you use it to power anything important.

Overall, it's a good power supply and I really like it.

I'm glad to see a nice-looking, nice-working power supply at low cost.  And I'm glad to see it's based on traditional components such as the 2N3055 power transistor.  Old-school!  This is how electronics should be made:  so that you can actually replace parts if they go bad. 

Other manufacturers should take a page from this playbook.  Forget the surface-mount devices and insta-fail caps hidden by layers of non-removable molded plastic.  We want traditional circuit boards, metal chassis, and discrete components.  In other words, the way electronics used to be made.

Yes, the instructions they include with the unit could be better;  but I'm sure if they'd put more effort into that, it would have increased the cost.  I'm happy with the price the way it is.   The power supply is a great value.  It's so good, in fact, that it would be worth buying two of them.  Yep, I like this unit that much, and the price is right.

You can use this device as a voltmeter or as a DC power source for your hobby projects. 

Order one of these power supplies and have some fun.  Because there are different brand names and the links seem to change, I added a few more.  Try this link, this one, or this one.  Also try this Ebay link;  you should find at least a couple of them in the results.


If you found this page useful, informative, or entertaining, please help me out by purchasing your stuff through these links.   It's the only way I can keep this website on-line and adding more articles to it.

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