Korad KA3005D Digital variable power supply (bought Nov 2017)

[Decoman]

Being new to electronics and having spent some time wondering that variable power supply I would want to buy, I was charmed for some time by the front panel of the KA3005D and decided to go for that one, knowing such cheaper power supplies might be iffy one way or another. A similar design was reviewed in 2012 I think by EVVblog, which didn't fare well in testing at the time.

As I understand it, this unit offer 5A of power at 110V and 3A of power at 220V. For a total of eh 660W max output if I can just multiply the amps with the volts. (I don't expect to ever use this much power myself or I would buy something else I am sure.)

I have not yet used this thing, I have not even turned it on. I thought it could be interesting for those wondering what this thing would look like, years after they started selling this model. My impression from reading this forum and watching youtube videos, is that there seem to have been some changes, and not knowing what I would end up with, I had hoped that this unit of mine would at least be an improved version, though I can't account for any changes per se.

Because I am new to all of this, I am not comfortable recommending this unit to anyone, but I thought sharing some photos could be interesting for those wondering what it might look like in 2017.

The unit of mine was packed in some more or less fancy Korad packaging, sold by SRA. The box seemed to have too little glue though, as two sides came loose on packing out this thing.
The unit was placed in a large zip loc bag together with a small humidity collecting bag (iirc). A manual in English, some probes and a 1m US power cable was also included, and separately packed in plastic bags.

Good things so far:
• Nothing rattling inside when I carefully flipped the unit around.
• The buttons on the front feels ok when I press each of them.
• The unit seem to have grounding wires inside, and they seem to be firmly attached with a screw and a jagged washer.
• As I started to take off the top part of the painted metal chassis, I thought the screws for the chassis was fairly tight, but not too tight. (Btw, one screw on each side, rear side, also has a jagged washer.)
• The fuse section of this unit, apparently has a small room containing an additional 5A, 250V glass fuse). Unsure if having some other fuse is ideal or not for a power supply connected to 230V.

Bad things so far:
• The "Korad" logo was only halfway printed on the front display, the lower half.
• The components inside seem to have a little bit of some fine dust all over.
• The strip of stripped paint on the upper and lower chassis, which I think must be the way the top chassis is grounded to the bottom part, seems a little too casual imo. Probably a good idea to tighten the screws well

Some things I've been wondering about:
• Not sure what to think about the glass fuse, as I have heard that there are something called HCR fuses as well, that I naviely think of as a possible improvement, but I could be wrong.
• I don't like the stripped paint parts for what might be creating a connection for ground, between top and bottom part of the chassis, maybe I could carefully remove some more paint?
• I wonder how long the mechanical power button switch will last.
• Will the power button safely cut the power as per design, or do I risk having the unit still output power when the power button is in the OFF state when something goes wrong with the unit?
• I will guess that the fan will be somewhat loud, which I won't like. Modding the fan might perhaps not be safe I fear. The fan sucks the air out btw, I initially imagined that the fan blew air into the unit, but I guess there would be too much dust going into the unit that way.
• The photos show some white paste around some components, I wonder what that is. I guess it could be some kind of special type of glue for electronics.

The photos (Note, I have since taking the photos flipped the 110V switch over to 220V on the back side of the unit, and I have to buy a new "Euro" C16 C13 power cable to get to use this unit anyway):

[Terry01]

Hi buddy. I'm new to electronics too,around a year or so but very much hobby orientated. I am teaching myself something that I know nothing about! All I have learned has been from YouTube videos and forums like this one. I love it!
I bought the Tenma 30V 5A version of this power supply around a year ago. It has been fine for me learning on and although I haven't really pushed it hard or asked a lot from it,mostly just kits or breadboard stuff I would say its a good unit. I think it's quite safe too which is good for new guys. Lots of sparks and smoke and it still powers up fine after each "mistake" 

I hope you enjoy yours as much as I have mine.   

[bd139]

Random question: How noisy is the fan on the Tenma one from your experience?

To original poster - thanks for posting this. Much appreciated 

[tooki]

As I understand it, this unit offer 5A of power at 110V and 3A of power at 220V. For a total of eh 660W max output if I can just multiply the amps with the volts. (I don't expect to ever use this much power myself or I would buy something else I am sure.)

You understand wrong. The output current is not dependent on the input voltage! This power supply is 30V/5A output. That’s 150W output, because VxA=W.

The fact that it needs 3A or 5A fuses depending on the input voltage is because at the higher input voltage, it needs fewer amps to draw the needed watts (because VxA=W, so W/V=A). 120Vx5A=600W. 600W/230V= 2.6A, so they went with a 3A fuse.

Basically, when used on 120V, it needs to draw more amps from the socket, when used on 230V, it draws fewer amps. But in both cases, the transformer converts it; you can think of it conceptually as the transformer converting the incoming power into abstract watts of magnetic energy, and then turning them into what it needs on the output.

• The fuse section of this unit, apparently has a small room containing an additional 5A, 250V glass fuse). Unsure if having some other fuse is ideal or not for a power supply connected to 230V.

It tells you on the rear panel which fuse to use for the supply voltage you’re using. Do what it says!! (For you, it’s 230V, so you must insert a 3A fuse.)

Random question: How noisy is the fan on the Tenma one from your experience?

Korad makes the Tenma versions. The fan is a bit annoying, to be honest (I have the Korad KA3005P, the same as this but with USB port). I modded the housing to remove the fan grille stamped into the housing and replaced it with a separate, thin wire grille, but it made little difference; most of the noise is turbulence along the heatsink. (The fan is actually quite quiet when running in free air.)

[Terry01]

The fan is really quite quiet, it doesn't bother me at all. It runs very smoothly so no rattles or squeaking or anything like that, just a gentle purr. I would highly recommend it as a power supply albeit from a limited knowledge base.
I've fried a few things and had sparks and smoke on a couple of occasions and its always came back on right after I've cleared the problem. Even when I've cooked a couple things on the trot it still fires up no sweat.

[Mr. Scram]

Random question: How noisy is the fan on the Tenma one from your experience?

To original poster - thanks for posting this. Much appreciated 

I have the dual output version and it's certainly not quiet. I think newer version might have a different internal heatsink which improves things. Despite this I use it a lot more than my quieter and much more expensive GW-Instek unit. I really like its utilitarian design and the simple interface of the Korad. The GW-Instek is not as convenient to use, but has a better resolution and PC control which both have their uses. It's also much better built. You can see the injection moulds of the Korad have been used to death, but I still prefer the Korad for every day use.

[Decoman]

I wonder if the fan on my unit was supposed to be blowing air OUT of the chassis, and not into it. The fan itself has arrows on the side indicating what direction the fan is spinning and what direction the air is blowing.

With the fan blowing sucking air out of the unit, like now, the fan won't blow air onto the heatsink inside. Which seems a little inefficient to me.

Only good thing, might be that you get less dust inside the unit this way. Instead of sucking air into one opening, any dust included, with the fan blowing outwards, all the minor openings will suck in air instead, but with a weaker force I am sure.

[tooki]

On mine, the fan blows out.

[Yansi]

It seems Korad is making progress. At least they have made a custom heatsink. Remember what the first Korads had as a heatsink - i piece of a flat metal wit a parody of fins around and a fakin hell noisy fan.

However it seems they cheaped out on components.  My Korad is containing Nipon Chemicon capacitors as the filter (3x 2200uF/63V snapin). That was a big surprise!

I have modified the cooling a bit and slowed the fan using a series resistor. Done the mod on several units since then. Currently using two of these as my main supplies.

[kalel]

I would also assume it blows the air out, similar to the back fan of a computer. As for what is more effective, I don't know, but it should work as is.
Warm air heat gets to the heatsink and gets out helped by the fan.

It's true that computers also have a fan on the heatsink that blows inside. But some have passively cooled processors, and I would assume even in those that the fan on the back (when there is one) blows outside.

[Terry01]

I'll open mine up later today and post some images of the Tenma version for comparison. I did open it when I got it for a quick nosey but can't remember off hand if it was a decent heat sink or not.
I've had mine around 12 to 18 months, I got it from Farnell element 14. It'll be good to see if there are any differences inside or if they are exactly the same.
It's always good to have a reason to take things apart! 

[Avacee]

As for why the fan pushes the air out - it's so the newly warm air isn't blown over the internals.

If you are more worried about pulling dust into the enclosure then you could turn the fan around so it blows inwards and magnetically stick something like this to the back.
https://www.overclockers.co.uk/demciflex-dust-filter-80mm-square-black-white-cm-000-df.html

All my PC fans blow inwards with these over them to create positive pressure in the case so no dust enters via all the little holes, grills, etc.
Quick wipe with a lightly damp cloth or the hoover every few days and the inside of my PC case is still spotless after ~6 years.

[kalel]

As for why the fan pushes the air out - it's so the newly warm air isn't blown over the internals.

If you are more worried about pulling dust into the enclosure then you could turn the fan around so it blows inwards and magnetically stick something like this to the back.
https://www.overclockers.co.uk/demciflex-dust-filter-80mm-square-black-white-cm-000-df.html

All my PC fans blow inwards with these over them to create positive pressure in the case so no dust enters via all the little holes, grills, etc.
Quick wipe with a lightly damp cloth or the hoover every few days and the inside of my PC case is still spotless after ~6 years.

That's interesting, and after 6 years I cannot question you on if it works well or not (obviously it does), but if all of the fans blow inwards, where does the air escape?
My understanding is that we're not supposed to have pressure inside of the case, but rather keep the airflow as good as possible (so that there is no time for heat to accumulate inside of the case). Dust can be reduced with filters, but obviously filters will also reduce airflow to a point, but a positive effect is that also noise could be slightly reduced.

At least with the standard configuration, I've noticed most effect with back and back top fans blowing out, for me those are the most important fans to have, and to have good airflow capabilities. I've noticed much less effect with added side fans or front fans (with front fans blowing in, and side fans depending on the side). This will depend on the case of course. Some cases just offer better cooling with the same amount of fans than others.

[Mr. Scram]

There's still a huge discussion whether positive of negative pressure, as far as you can speak of that in a PC case is more effective against dust. However, from a cooling perspective, people generally agree that there should mostly be a balance between intake and outtake. This seems to be confirmed by experiments done by people. Some do this by slowing the fans on one side down or by adding or removing a fan on intake or outtake.

If you have all fans pointing in or out cooling will suffer, which is obviously ultimately the point of having fans in the first place. If you absolutely want to fight dust you could remove all fans completely, but that's not a good idea for the same reasons. The truth is that a proper airflow will contain more dust than an improper airflow, simply because the volume of air is bigger, and will likely carry more dust inside your case because of it.

[Kleinstein]

The heat sink looks much better than the old version. Using an extra board for the power resistors also looks odd, but I would guess it works.

The "coil" near the output terminal  looks a kind off odd - this might be the current shunt made from something like a maganin wire. I have seen worse.

[Yansi]

Yes, that is the output shunt.

Whats is wrong with that?

[Mr. Scram]

The heat sink looks much better than the old version. Using an extra board for the power resistors also looks odd, but I would guess it works.

The "coil" near the output terminal  looks a kind off odd - this might be the current shunt made from something like a maganin wire. I have seen worse.

Many devices do it that way, many of which are of a reputable make.

[stj]

throw the cables away.

[tooki]

What do the junky cables that come with a random chinese PSU have to do with the ones that come with this specific non-random model?

[stj]

take a close look at the pictures posted above.
it's the same chinese cables.

[Decoman]

What is an 'output shunt'? I mean, what is its intended purpose there?


Btw, the  detachable power chord for 110V that came with my unit was replaced with a locally bought 220V power chord (says "250VAC 10A" on it).

[bd139]

It's a small resistor that is used to measure the output current with the relationship I = V/R. You know R, so you can derive I from measuring V.

Everything from Chinese power supplies to high end Flukes use bent bits of wire for this job

[Decoman]

Btw, the power supply unit that is shown in stj's video, seem to have its fan arranged to suck air into the unit. Just an observation.

* watching the end of that video linked above* Oh, wow. The tester things that non copper was used, and instead "copper plated aluminium" for all the strands of metal inside that psu's wire cable. :O

[tooki]

take a close look at the pictures posted above.
it's the same chinese cables.

The power cords obviously are not the same, since they’re not even for the same country.

As for the alligator clip leads, they could be the same, or they could be entirely different inside — it’s impossible to tell without dismantling them. (My Korad didn’t come with alligator clip leads so I can’t volunteer to do this.)

[stj]

factory's churn out power cords for lots of country's - they dont each come from a seperate source.
anyway, it looks like you can spot them with an ohm-meter.
so that makes it simple to check.