Korad KKG305D/KKG305P

[xKertx]

Hello,
I think this power supply deserves its own thread because it's a little different than other Korad PSUs.

I made a small review of it:
https://youtu.be/-Rq0KUz-qd0?si=IHR3fmuLgAl-uS8O

This is my first review ever.
Also, sorry for my bad english. I'm from Finland and I don't speak English very often. 

Anyway, I think the main differences with other Korad models are:
Much better display.
Solid state relays, so no relay noise.
Better cooling.
Amp meter can go down to milliamps.

Unfortunately, the memory overwrite bug is still there.

[ataradov]

Is this a Noctua fan out of the box? Or is this a mod?

[xKertx]

Is this a Noctua fan out of the box? Or is this a mod?

I have replaced the fan with the Noctua NF-A8 (80x80x25mm).
The original fan made somekind of ticking noise. Now its almost silent. And i think the Noctua fan pushes little more air.

[ataradov]

It might be useful for the thread to know the exact model you used, so people won't have to guess what fits. Although all those fans are pretty much the same in size.

[xKertx]

It might be useful for the thread to know the exact model you used, so people won't have to guess what fits. Although all those fans are pretty much the same in size.

I have edited my previous post.
It's Noctua NF-A8.
But any 80mm fan will fit.

[5U4GB]

It's Noctua NF-A8.
But any 80mm fan will fit.

That's a PWM fan, does that mean it's got proper control or does it always run like the 3005D/P?  I was trying to see the connector in the video but it was a bit hard to see.

Thanks again for the video, it looks like a significant improvement over the 3005D/P series.

[xKertx]

That's a PWM fan, does that mean it's got proper control or does it always run like the 3005D/P?  I was trying to see the connector in the video but it was a bit hard to see.

Yes, it's a pwm fan, but if you leave the rpm and pwm wires unconnected and connect only + and -, then it will act like a normal fan.
I didn't have the right connector so i had to cut the wires and used the connector from the old fan.

It is always on, but it is on low speed by default. The fan is temperature controlled by the power supply so it will speed up when needed.

[ass20]

hi
Can you make photo of used ic ? what is cpu used on this korad?

[glitchcatcher]

Finally a thread about the KKGs! A bit of a weird product, hardly available and still not listed on the Korad website!
I have a Warsaw connection, so it was easy for me to get a KKG3010P last year at NDN. It was my choice of Korads because it fits the Korad KEL102/3 load perfectly with that green display

Unfortunately, the memory overwrite bug is still there.

On the German forums someone wrote about these KKGs and its improvements:
"The memories are no longer overwritten when you change the settings, but only at the touch of a button"
That is unfortunately also not true for my model.

Attached some pictures for comparison.
When I opened the case, I slid the cover backwards which was a mistake (and also unnecessary, all you need to do is grab the bottom at the sides and pull outwards, then lift up carefully).
The screw holding the case handle scratched the PCB! Too little clearance, and the PCB is also bending upwards a bit. A design flaw!

[ataradov]

Interesting that there is a handle. The pictures in the OP do not show it. And I mod my KA3005s with a regular furniture drawer handle, which makes them way easier to move.

[bingo600]

They're here - Not many other hits
https://ndn.com.pl/en/szukaj?controller=search&orderby=position&orderway=desc&search_query=kkg&submit_search=

[5U4GB]

Thanks for the additional photos, it looks like they've now got metal-to-metal contact on the struts and top case to try and earth the top part of the case rather than the somewhat dodgy mechanism described here:

Something that isn’t immediately obvious until you see the improved version, the earlier models didn’t earth the top part of the case, which is the bit you’d be most likely to touch of you’re handling it. They’ve fixed that in the current version by leaving a strip of bare metal along the base and then using locking washers on two of the screws which scrape the paint from the case and provide a metal-to-metal contact. Most likely fails every safety certification known to man, but it probably, um, works.

[xKertx]

hi
Can you make photo of used ic ? what is cpu used on this korad?

I finally had time to open it up again and swap the capacitors to Panasonic and Vishay long life caps.
I guess this is the chip you are talking about?
I think it has a "KORAD01" written on it and some other numbers. Really hard to tell because of the shiny laquere coating.

[feri666]

I have a Korad KKG305P power supply.
When I set the voltage between 7V and 15V, the voltage fluctuates between 7V and the set value. For example, if I set it to 12V, the voltage fluctuates between 7V and 12V, up and down, even without a load.
If I set the voltage lower than 7V or higher than 16V, it works normally.
What could be the problem? Which component could be faulty?

[5U4GB]

Sounds more like it could be a configuration error, do you have it in CC mode, or some sort of other limiting applied where it'd drop the voltage to compensate?

[krzys-iek]

Hello

I have just bought this one. Important question! This model is loud - buzzing noise coming from transformer winds. Always, w/o and with load. Typical low pitch buzz from the mains 50/60Hz. WHY? It then travels (this sound, so small vibrations) onto my desk etc. Very annoying! Old model did not have that, it was silent.

Is it same with your model guys? I wished for upgrade but keeping that on for hours will drive me crazy!

[xKertx]

Sounds like a faulty unit. I would return it.
Mine is dead silent (after i replaced the fan) and no vibration.

[krzys-iek]

Thanks, will do so. Crap...

Mod time, did you replace green led for OUT? I wish they gave different color for that one. Easy to miss that output is ON when ALL the info is green lit! Is not it? I wish it had different LED colors for ON/ CV /CC dont you think?

I dont know if you have took it apart (hehe Dave) deep enought to spot if these are SMD LED or THT 3mm ones? And if V accross this LED is okay to just resolder other popular color.

[xKertx]

Yeah, it would be nice if the backlight of the "out" text could be replaced to red one.
But i have not disassembled it that far.
When examing it with a flashlight, it seems that the whole display is a one single panel.
So i guess it would be real PITA to disassembly it. First you need to desolder it and then somehow cut out the backlight led of this digit. Then glue a new one in and solder the whole thing back to pcb.

I've been thinking if it would be possible to just connect another red LED in parallel with the existing "out" text. A red led somewhere on the screen would be better than nothing i guess.

[krzys-iek]

Thanks, ahhhh Korad! Other solution is RED backlight of the on/off switch itself. Seen that on cheep UNI-T models. Now we have "matrix" green all other the place so as ppl say - easy to miss that output is ON!
CV, CC also should not be green! Old version clearly manifested that we are in CC mode or output is ON.

Overall this model they say is a step forward and better. But small things should be thought before they release. Even asking here and then drawing conclusions. Red backlight is not more expensive to make for sure so why not to do that?
Handle to carry would be nice bonus too, with a possibility to unscrew it if you do not needed it.

PS
Rubber of on/off switch I guess is not transucent even for strong LED? You know just to shine thru. That would be probably easy to do w/o any need to drill etc. I have sent my buzzzzzzy model back to shop and will be getting a replacement.

[krzys-iek]

I got a new one, this one produces even more annoying buzz  what the f... 

[Pfriemler]

I have a Korad KKG305P power supply.
When I set the voltage between 7V and 15V, the voltage fluctuates between 7V and the set value. For example, if I set it to 12V, the voltage fluctuates between 7V and 12V, up and down, even without a load.
If I set the voltage lower than 7V or higher than 16V, it works normally.
What could be the problem? Which component could be faulty?

I know it’s been almost a year, but a similar problem and its solution just popped up on the German website Mikrokontroller.net.

https://www.mikrocontroller.net/topic/586366#8077341

In short: The transformer has multiple windings, and switching between the windings depending on the output voltage is not done with relays, as is usually the case with Korad, but with triacs. Additionally, there are fuses in the transformer’s wiring. One of the fuses had blown, and the power supply is working perfectly again after the repair.

THX to DeepL

[Pfriemler]

Now I got me a KKG305D and need some informations about the back side clamps.
- "SENSE+"/"SENSE-" is easy 
- "ON" is activated when the output is active. A voltage of ~14.15 v is measured @ 230 volts mains (changing with it), a small ripple of 100 50 Hz. Looks like a internal raw unstabilized power supply. Load of 10 mA -> 13.7 v.
- "CC/CV": Same in CC mode (CV = 0 volts).
Any idea how much current I may draw without damaging the unit? is 10 mA reasonable or too much?
No, you can find nothing about this in any manual I got. BTW: there's a calibration procedure available like for the KA series.

---

In addition, I examined the TRIG/OUT behaviour to enable/disable the output, depending on the setting in the menu.
“1,”: TRIG/OUT only turns the output on, but not off. Turning the output on and off is still done using the front panel button.
“2,”:  TRIG/OUT turns the output on as long as the signal is pulled to GND. In this case, it is no longer possible to override the status using the front panel button—although the display may flicker briefly, the output remains in the state specified by TRIG/OUT.
The text “TRIG/OUT” appears permanently on the display as soon as the setting is set to “1” or “2” (the signal is not displayed).

In mode “1,” TRIG/OUT functions not only as a pulse but also, as in “2,” as a default setting; thus, the output cannot be deactivated as long as the signal is present. However, the shutdown described in “2” does not occur when TRIG/OUT becomes inactive.

In this context, a bug has been noticed: The priority circuit even overrides the OCP protection feature, rendering it useless. For example, if I set the current limit to 1 A and OCP to 0.5 A and then short-circuit the output, I can turn the output on using the front panel button; OCP will then sound a beep, and the output will turn off. However, using the TRIG/OUT signal, it is possible to keep the output active; the OCP beep sounds a few times—and then the OCP turns off and the output remains active within the current limit.

[Pfriemler]

Some news:

- "ON" is activated when the output is active. ... "CC/CV": Same in CC mode (CV = 0 volts).
Any idea how much current I may draw without damaging the unit?

Krissy Yang from KORAD Support answered: 0.1 A is ok without damaging the device. I did a review of the parts: There's a separate transformer winding 12V, half-rectifying, 470/25; outputs are MOSFET switched with 2x 10R (not the smallest one) in series. 2K to GND and a diode for reverse polarity protection. Optocouplers on the power board for ON and CC/CV signaling and reverse for the TRIG/OUT input. Well done, KORAD! If you blow up something there, it will be easily replaced.

If not already mentioned above:
- output capacitance 330/50, two "103" (?) caps to Earth Wire. Far too much for me, but usual.
- relay to switch internal/external sense
- ATTENTION: up to 14V output if only one sense line is connected. Some resistors or diodes connecting internal/external sense will help, easy to install on the power board, only the cover has to be removed.
- fake 20..50 mA current if a protection diode is used in the + output to charge batterys (sense+ after diode). Also reduced current in CC mode. No problems if the diode is used in the (-) line.

And no chance to change the color of ON, CV, CV in the display: it's a encapsulated custom LED module, no way to get into, as xKertx mentioned before.
BUT: Besides the mains switch there's a rectangular hole in the front, only covered by the description sticker. You may place some bright LED behind to get a 10x5 mm light field, on the left of the output clamps, no need to make holes, I made a short test. ON and CC/CV outputs will give enough power. If you may live with two separate LEDs (and both lit in CC mode), you only need two LED and two resistors and some cable for a safe solution. I will do this later.

Transformer windings are switched with a (surprisingly) small hysteresis of only 0.1 v, depending on the output voltage (not the real raw DC, which will change with the mains voltage).
1->2 6.9 V; 2->1 6.8 V
2->3 15.4 V; 3->2 15.3 V
3->4 22.3 V; 4>3 22.2 V

Maximum power output 31*5.1 = 158, while consuming 280 W from mains (56%). Unloaded ~14 W, similar to my KA3005P.
Cooler fan is powered from a unregulated supply, thus significant slower under heavy load, and turns up when load is off. Just as my KA3005 does.
Fan has significant lower noise than KA3005, even compared to my silent Welectron edition.

I don't like the voltage/current settings, the KA3005 is better to handle.

Nevertheless: To me, it's the way more useful device compared to the KA3005, for ~ the same money (D model via botland.pl).
I hope I will never blow up my transformer windings fuses, let's see...