Lavolta 30V 5A Power Supply with Handle - Variable Regulated Adjustable Linear DC Lab Kit with Alligator Leads and US Power Cord

The media could not be loaded. Review of Lavolta BPS-305 DC Power Supply 12 Jan 2018This is almost a 5-star power supply but for some 1-star flaws, so I am giving it a 3.PROs, some 5-star features:1) Linear (analog) with a robust 50/60 Hz power transformer, ie. electrically quiet output (no switching noise). Clean, solid construction.2) Looks mostly good inside, a few not-so-good internal interconnections (sloppy solder joints) but the modules themselves look good.3) The first paragraph in the "User Manual" warns about turning On or Off the Power switch with a load connected. This is contrary to how I , and I believe many (most ?) users operate the PS when experimenting on the workbench. I tested the BPS-305 using various (non-inductive) loads at various combinations of high and low voltage and high and low currents while observing the voltage at the load with an oscilloscope and saw no voltage transients...the PS has a "soft" turn-on and turn-off for all combinations including Constant Current mode. I will however adhere to their admonition regards inductive loads.CONs, some 1-star "features"1) If the load current to the device you are powering is using low currents from a few mA to a few hundred mA the CURRENT readout exhibits significant error because the resolution of the least-significant digit is 10 mA.The accompanying graph shows the CURRENT reading error when operating with low-current loads.An example of the absolute worst case is where the load current is 12 mA...the CURRENT readout is zero! The next-worse example is if the load current is 22 or 23 mA, the CURRENT readout is only 10 mA...a greater than 50 % error. As seen on the graph, as the load current increases into the hundreds-of mA range, the error falls to a few percent. There is a work-around for this problem that I will explain further along.2) The test leads are complete crap. Two fatal problems, the occurrence of either could lead a non-experienced user to falsely conclude that the power supply is not working. a. Black lead, alligator end. The wire solder joint had failed. See photo. The red lead is soldered but looks marginal. b. Red lead, banana end. This iss a really bizarre fault, difficult to describe with words, best seen, as in the accompanying short MOV clip. The moving spring-like round part makes good contact with the PS "+" terminal but the red lead connected to the load is fastened to the part being held in my fingers.The effect of this fault is seen in the scope screenshot as observed at the load when the red lead is moved or jiggled. The output of the supply is clean and steady, it is the load end that is intermittent. How well do you suppose the circuit being powered will operate with power like this? c. Red and Black leads. The plastic covers over the alligators feel like they are coated inside with grease. They aren't of course, this feeling is simply a characteristic of many ChiCom alligator clips that use this slicker-than-snot type of plastic wherein when the user grips the alligator and squeezes to open it, it slips sideways inside the cover.Not the-end-of- the-world-as-we-know-it but annoying nonetheless.***************************************************************Non-Star related. Here are a couple of simple hacks that will make the PS more user-friendly.1) A work-around for CON 1 is to use a cheap (or free with a coupon) Harbor Freight DMM to measure low load currents. See the photo...it's self-explanatory.2) Need more than 30V? I have a some high-power LEDs that want at least 32 V to operate properly so I looked inside, saw some trimpots, and found the one that sets the max Vout and adjusted it to the max-output stop and now can get a little over 36V! See photo for this pot location.A note of caution!! In any piece of equipment that has adjustment pots that have no meaningful markings, if you are wanting to make some parameter change but have no clue as to which pot might be the one (if there even is one), a safe way to do this with little risk of completely screwing-up the device is this: 1) choose one to start with, make a reference mark that shows where the pot is currently set. 2) adjust the pot first one way and then the other and observe if this pot does what you want. 3) if not, set it back to the reference mark then choose another pot and repeat with it. There is no guarantee that you will be able to change what you want to, but if not, at least you can return the settings back to where they were.The photo shows which pot I used to increase the maximum output voltage.*************************************************************Final word... overall, a nice power supply with some unhappy, but fixable problems. Would I recommend this PS to a friend? Yes, but with the caveats.

Although I havent done extensive testing with the unit, I can honestly say from the first quick tests I am impressed with such a cheap unit. I ran it through my multimeter. Measuring the volts and amps at different levels, they were no more than a few hundredths off to a few tenths off. It appears to have a decent build quality. Its definitely has some heft, although I havent opened it to check it out on the inside. The case is all metal (I want to check inside and see if its properly grounded), except for the front panel which is plastic. The red LCD is easy to read. Right below the voltage and amperage display are some tiny holes in the front panel that reveal two tiny potentiometers inside to adjust their levels. The 4 main potentiometers have a decent feel, requiring some actual finger torque to spin them. There is an amp hi/low button that limits the amps to 5/2.5A, which I guess could be considered a safety feature. Also, it sits on 4 decent rubber feet, With the feet and the weight of the unit, Im confident this unit will stay where it is and not move or tip over.So far, I havent come across many issues. The test leads it ships with are rather short and cheap (one alligator clip on mine was no good), you will want to switch those out. It has a - (negative terminal), but nothings appears to be connected to it. Other people mentioned that in the reviews, so I knew that going in. The only other negative I found so far is I think the fan is a little loud. When I open it up, Ill see if I can replace it with a quieter one.I havent tested constant current of constant voltage yet, or any other features. When I do, I will try to remember to update the review.In the end, I very happy with it. For the prince, I dont think you can do better.

This product is crap. I received it and the first thing I noticed was that the power cord was not included, but that was only the tip of the iceberg.When I found a spare IEC power cable, I attempted to power this thing up. The fan turns on ok but that was it. Nothing on the display and no output voltage whatsoever.I decided to take the top off this product and was exposed to pure carnage in the form of unplugged wires, terrible soldering, and what amounts to simply a dangerous, and badly designed product. But don't take my word for it, check out the photos.First thing I noticed was the unplugged connector (CN303) - that was easy enough to fix, I just plugged it in. Next thing was the detached wire that looks like it used to be connected to GND (near the net V_IN - V_IN+ silkscreen).. I went ahead and resoldered that while cringing at the burn marks that were left on nearby wires due to a s***ty technician's work at the factory. I powered the power supply back on and the display turned on! But everything was showing 0's despite what I did with the V and I knobs, and my multimeter verified absolutely no output voltage. After unplugging the device I noticed a few more things: a broken track on the main DC to DC conversion PCB, a bunch of through hole parts flapping in the breeze, no mains input protection other than a fuse, and almost every wire in the product directly soldered to PCBs or the mains connector. Oh, and how can I forget the bridge rectifier just screwed down straight to the case, with minimal heat shrink insulating its pins from the aluminum enclosure. Or maybe the mains wires strung across the side of the aluminum enclosure rubbing against the corners of the transformer and flapping around.I repaired the broken trace on the board and was finally able to get variable output voltage (that was even within spec!), but when I shorted the output and tried to limit current I couldn't. There was only one setting for current: Maximum. I'm assuming there are more broken traces/shorted leads/s***ty soldering contributing to constant current not working but I don't know if I have the time or patience to trace everything out.If for some reason you decided to use this device make damn sure your outlet is actually earthed. This product says it is UL listed but after seeing what I saw inside there I highly doubt it.