Korad KD3005D bench supply power on spike

[Electro Fan]

Another at 200ms

Edit:  added adapter image

[Electro Fan]

Article mentioning bandwidth limit.

https://www.eetimes.com/power-tip-6-accurately-measuring-power-supply-ripple/#

I think Dave did a video on measuring ripple that also cited the use of a bw limit for measuring ripple.

[Electro Fan]

This article that also talks about using a bandwidth limit to measure ripple gives examples at 1us.

https://www.digikey.de/Web%20Export/Supplier%20Content/Excelsys_633/PDF/excelsys-measuring-ripple-noise.pdf

At 1us the Korad is under 1mVRMS and averages about 3.5mV pk-pk.

[vikisonline]

Your trigger is way in the band though, try moving it further out and see if you see occasional spikes

[Electro Fan]

Your trigger is way in the band though, try moving it further out and see if you see occasional spikes

Here are two more, both with the trigger at 14.9mV; one was 1us the other was 200ms (should be plenty of time to find ripple).

The ripple was a little higher than previously - my guess is something (other test equipment, computers, lights, air conditioning, who knows what) was off last time and was on this time.  Let me know if you want something else tested.

At around $100 per power supply for the KA3005D model I think it's possible that there might be some unit to unit variation and it's possible that some units will be defective or out of spec but I think Korad is generally likely to meet or come pretty close it's specs most of the time.  If you buy from a reputable seller hopefully you can return it if it doesn't meet specs. 

Regarding ripple measurements I think some keys are 1. measuring with a very good connection (preferably with a probe to BNC adapter), 2. use a 20MHz bandwidth setting, and 3. be careful to distinguish between PS ripple and environment noise. 

[Electro Fan]

After the several minutes it took to post above I looked again and saw the ripple was reduced somewhat.  My guess is something nearby shut off in the meantime.  I'm pretty sure that at somewhere around 1 to 3mVRMS it's possible that something starts acting like an antenna and that a variety of things can be transmitters.

[xani]

At around $100 per power supply for the KA3005D model I think it's possible that there might be some unit to unit variation and it's possible that some units will be defective or out of spec but I think Korad is generally likely to meet or come pretty close it's specs most of the time.  If you buy from a reputable seller hopefully you can return it if it doesn't meet specs. 

My KA3005D-3S had 12V rated fans powered by 24V. I only noticed when they died after few years of occasional uses. But power is clean without spikes...

[vikisonline]

Yea unit to unit variation might be my guess. But for the price Im happy with it. I didn't get as lucky as some others but this will do for now.
Thanks for running those tests.

[vikisonline]

At around $100 per power supply for the KA3005D model I think it's possible that there might be some unit to unit variation and it's possible that some units will be defective or out of spec but I think Korad is generally likely to meet or come pretty close it's specs most of the time.  If you buy from a reputable seller hopefully you can return it if it doesn't meet specs. 

My KA3005D-3S had 12V rated fans powered by 24V. I only noticed when they died after few years of occasional uses. But power is clean without spikes...

HA. That is one of the good things about mine. Even on full power (30v 5A setting drawing 1 amp) the fan in mine is quieter than my rigol scope... Go figure.
From others I heard it would be horribly loud but I guess I got lucky with that part.

[DaneLaw]

Aint these temperature-controlled to an extent that the fan will turn off with no load? been a few revisions.
so a given fan-noise on a KA-unit, like almost a decade back, can vary quite a bit from a buyer purchasing one today.

Got the KA3003-P model and the KD3005-P model.. the KA3003P were from China and the KD3005P from Europe (purchased 4 to 5 years back).
Took a look inside #17 (KA3003-P model) to put my unit ino perspective with the unit Dave got' but I do recall my KD-5A model was more silent than my KA-3A model.
but the very early models like 9 years back, had some challenges, like Dave is pointing out here, but were fixed very soon after by Korad, and made these Korad-PSUs to be some of the most popular lowbudget linear PSU's for the hobbyist's

--
and the follow-up after Korad changed it... https://youtu.be/_HrvuHSywms?t=137

Here is a fan noise-display of my KD3005P with a full 5.1A load on a Nichia-laser diode peeking around 6.3w. .

[Electro Fan]

At around $100 per power supply for the KA3005D model I think it's possible that there might be some unit to unit variation and it's possible that some units will be defective or out of spec but I think Korad is generally likely to meet or come pretty close it's specs most of the time.  If you buy from a reputable seller hopefully you can return it if it doesn't meet specs. 

My KA3005D-3S had 12V rated fans powered by 24V. I only noticed when they died after few years of occasional uses. But power is clean without spikes...

HA. That is one of the good things about mine. Even on full power (30v 5A setting drawing 1 amp) the fan in mine is quieter than my rigol scope... Go figure.
From others I heard it would be horribly loud but I guess I got lucky with that part.

If you want to see what the power supply really can do on the ripple measurement I think it's best to test using one of these:

https://app.caltestelectronics.com/product-list/product-page/view/CT3655/

They come in different sizes - just make sure to get one that will fit the oscilloscope probe you are using.

https://www.farnell.com/cad/2702874.pdf

This 3.5mm adapter fits a Rigol RP3300A.  Some of the older Tektronix probes I think require a slightly larger adapter.

Edit:  you need one of these too, of course

https://www.pomonaelectronics.com/products/adapters/bnc-f-double-stacking-banana-plug