Author Topic: Inside the new Korad KA3305P linear PSU  (Read 59202 times)

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Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #100 on: December 17, 2015, 07:18:55 pm »
Info: The way you set Over Current and Over Voltage protection is very easy.

I found it by looking at the screen, and noticing that there was a "SET" light besides the indicator lights for OVP and OCP.

Basically, if you push and hold the OVP or OCP buttons, first one then the other, or separately ofc, both channels will display the currently set OVP and OCP values, as long as SET is glowing next to OCP or OVP, you can set it just like you set the voltage and current during normal operation.
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #101 on: December 18, 2015, 01:50:50 am »

The only issue I have met, is that one time I powered it on, it turned on with the output on !!
I think it was because of the settings in the software? I've been unable to replicate it.


Mine powers up in the "on" state if it was powered down in the "on" state and vise-versa.

Quote
Alos, the most noisy thing is the regulators for the fan, they keep buzzing, changing with the pitch of the fan...

Mine don't buzz. Maybe yours has a bit of a gap between a heat sink and the board?

I'm curious, does yours have the serial mode bug that mine exhibits with my replacement board? IE: When Serial mode is selected with the output turned off, the current limit is displayed as 0.000 on both channels. (although it works properly and displays properly when setting the current).
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #102 on: December 18, 2015, 06:49:52 am »
I'm curious, does yours have the serial mode bug that mine exhibits with my replacement board? IE: When Serial mode is selected with the output turned off, the current limit is displayed as 0.000 on both channels. (although it works properly and displays properly when setting the current).

Yup, It does the same thing. Ofc, I set the current limit on CH2 and it changes on both channels.

Also, the most noisy thing is the regulators for the fan, they keep buzzing, changing with the pitch of the fan...

Mine don't buzz. Maybe yours has a bit of a gap between a heat sink and the board?

Well, they/it will start making a buzzing/grinding sound about 45 to 60 seconds after I turn it on, with no load.
I had the cover off, and it looks like it applies very low power to the fan at this stage, PWM? it doesn't spin on it's own, but starts if I give it a little help. The fan spins easily though, so it's working as it should, also it starts on it's own if I leave it alone long enough.
« Last Edit: December 18, 2015, 06:56:17 am by SantaClaw »
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #103 on: December 18, 2015, 12:58:02 pm »
Yup, It does the same thing. Ofc, I set the current limit on CH2 and it changes on both channels.

Yes, Ch2 is the master.
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #104 on: December 18, 2015, 01:31:41 pm »
Yes, Ch2 is the master.

Yup, both in Parallel and Series :)
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #105 on: December 19, 2015, 02:29:59 am »
Nice feature though:

If you are using the USB interface and you turn off the program, or disconnect the USB with the output ON, the buttons will automatically LOCK, as if you push and hold the CH1 coder wheel (hold it down to unlock the buttons).

Not that nice feature though:

When opening the USB interface program, If the PSU output is on with a set current and voltage, well basically it don't matter,  the meter will turn the outputs OFF, and it will automatically set current/voltage /ocp/ovp to what ever the program is set to on default, in my case, it jumped from 5V/500mA to 31V/5.1A on both channels, disaster if I had just hit the output on button.  SO, be really freaking careful !!
« Last Edit: December 19, 2015, 02:33:32 am by SantaClaw »
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #106 on: December 19, 2015, 02:55:43 am »
I have been swamped and not had time to play further with the software, but IIRC, that behaviour is in the software, not the firmware. I think the software is sending the "lock" command and other settings when it first boots up.

When time permits, I'm going to take a stab at creating better software for it. Particularly the program scripting. I have figured out the protocols, so it's a start...
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #107 on: December 19, 2015, 03:57:06 pm »
Sounds great, btw,with both channels set to 5v, no load I measured 5.00v on ch1 and ch2, but I "only" get 4.98v on ch3 in the 40v range. I just ordered myself a new siglent SDM3055 bench meter, Hopefully IT will be a little more "trustable" than my uni-T :D
 

Offline Kkkkkk

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Re: Inside the new Korad KA3305P linear PSU
« Reply #108 on: January 24, 2016, 10:49:38 am »
Stupid question :
When I use the KOARD 3305 in series operation can I fire it up to 60 volts
and in parallel up to 10 amps?

Thx
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #109 on: January 24, 2016, 10:58:58 am »
I believe it's, 31v 10A in parallel or 62v 5A in series max output.. Yup, confirmed, only got 3a when set to 3a on CH2 and CH1 in series.
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #110 on: January 24, 2016, 04:40:14 pm »
Yes, it can supply either a maximum of 5A (5.1A actually, IIRC) at 62v when connected in series OR a maximum of 10A (10.2A) at 31v when connected in parallel.
 

Online Kleinstein

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Re: Inside the new Korad KA3305P linear PSU
« Reply #111 on: January 24, 2016, 05:41:13 pm »
You may not get the maximum voltage and maximum current from both channels at the same time, especially if the line voltage is at the low end. These cheap supplies are usually don't have filter caps that have much reserve to compensate for lower line voltage - adding more capacitance could also overload the transformer, so this is not a good idea. So just don't count of the full 5 A at 30 V, depending on the tolerances and line voltage it might be only 4 A at 30 V or 28 V at 5 A before ripple comes through. 
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #112 on: January 24, 2016, 06:32:48 pm »
It had no problem providing 10A dead short when in paralell
 

Offline Kkkkkk

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Re: Inside the new Korad KA3305P linear PSU
« Reply #113 on: January 24, 2016, 06:40:56 pm »
Thx for the quick response.
That's what I was asking for. Possible max voltage OR max current.
The technical data sheet and the manuals from KOARD are really crappie  :bullshit:
I know running equipment on its upper limit is always gambling and you
pray that Chinese work with safety margins, too.
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #114 on: January 24, 2016, 07:09:24 pm »
It had no problem providing 10A dead short when in paralell

Yes, but the voltage drops off to next-to-nothing with a dead short because the unit goes into constant current mode.

I think Keinstein is making reference to possible voltage sag, wherein the voltage drops off before the unit starts limiting the current because the transformer just can't deliver the wattage. Especially likely if the line voltage going into the transformer is low.

I did some testing when I bought this, first with a carbon pile (which did not have a fine enough adjustment for precision) then stringing together 100w (120v) light bulbs in parallel to provide a load. I forget the exact numbers, but I snuck up on 5 amps @ 60v by adding more and more bulbs until I was just shy with no voltage sag. Adding one more bulb triggered the CC mode, which throttles the voltage to limit the current. I neglected to draw anything from Channel 3 during the test, but the Korad can at least deliver full power through 2 of the 3 channels simultaneously.

FWIW, when I asked the vendor, he replied the weak link would be failure of the cooling fan on the internal heatsink, but as long as the fan keeps going it can supply full power indefinitely.

But then, taking a vendor's word could be like buying a used car from the guy who swears it was only driven by a little old lady to church on Sundays...  :-\

 

Offline Gall

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Re: Inside the new Korad KA3305P linear PSU
« Reply #115 on: February 29, 2016, 08:43:10 am »
Hi,
I wonder how the series mode work. I'd like to use it for an opamp dual supply. Does it work just as two independent power supplies of the same voltage connected in series, or do their voltages follow each other in case of overloading (going to the CC mode) just one of them?
The difficult we do today; the impossible takes a little longer.
 

Offline torch

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Re: Inside the new Korad KA3305P linear PSU
« Reply #116 on: February 29, 2016, 12:38:24 pm »
I did not know, nor had I thought to check. So I just did a quick experiment.

Series mode, 3vdc per channel, (6vdc total ch.1+ to ch.2 -), current limit to 1.1 amp per channel,

metering  ch. 1 + to ch. 1 -,
shorting ch. 2 + to ch. 2 - :
ch. 1 continues to supply 3vdc, ch. 2 switches to CC mode @1.1A

metering ch. 2 + to ch.2 -,
shorting ch. 1 + to ch. 1 - :
ch. 2 continues to supply 3vdc, ch. 1 switches to CC mode @1.1A

metering ch. 1 + to ch.2 -,
shorting ch. 1 + to ch. 2 - :
both channels drop to 0vdc, both channels switch to CC mode @1.1A each

So I would say it behaves like 2 independent supplies in the case of overload.

(as noted earlier, in both series and parallel modes, ch.2 is the master. ie: the set points of ch.1 are changed to mirror the existing set points of ch.2 when entering either mode. changing ch.2 set points changes ch.1, and ch.1 controls are no longer available)

Hi,
I wonder how the series mode work. I'd like to use it for an opamp dual supply. Does it work just as two independent power supplies of the same voltage connected in series, or do their voltages follow each other in case of overloading (going to the CC mode) just one of them?
 

Offline Gall

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Re: Inside the new Korad KA3305P linear PSU
« Reply #117 on: February 29, 2016, 04:48:47 pm »
Thank you. That means, a dual-supply circuit will become an asymmetric power in case of overload. I wonder how hard it would be to fix that...
The difficult we do today; the impossible takes a little longer.
 

Offline Aeternam

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Re: Inside the new Korad KA3305P linear PSU
« Reply #118 on: March 06, 2016, 02:01:47 pm »
I have one of these and I've been very happy with it.

I've recently hooked it to my scope to see how it was behaving, and I've noticed some strange ripples when I turn it off when the output is set to OFF (see attachments). Is this something I should be worried about? I'd hate to have to disconnect the leads when I turn it off to go watch some telly...

Also, it makes a quite audible GONG sound when I turn it on. (Not always though.) Is this designed so that you're awake when you start using it?  ;D
 

Offline mos6502

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Re: Inside the new Korad KA3305P linear PSU
« Reply #119 on: March 18, 2016, 12:28:24 am »
I have one of these and I've been very happy with it.

I've recently hooked it to my scope to see how it was behaving, and I've noticed some strange ripples when I turn it off when the output is set to OFF (see attachments). Is this something I should be worried about? I'd hate to have to disconnect the leads when I turn it off to go watch some telly...

Also, it makes a quite audible GONG sound when I turn it on. (Not always though.) Is this designed so that you're awake when you start using it?  ;D

When the output is off, it's high impedance. You're just picking up random noise with your scope. To test this, just hook up a 1k resistor at the output.

As for the *boink* sound: say when you turn the supply off, the switch opens exactly at the top of the positive half wave. The transformer core will remain magnetized in that direction. Then when you turn it on again, you might turn it on at the top of the negative half wave. The winding will create a magnetic field that is opposite to the already existing field of the core. So you get an instantaneous mechanical force of the winding pushing against the core. It's kinda like the transformer is being hit with a hammer.
for(;;);
 

Offline YottaByte

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Re: Inside the new Korad KA3305P linear PSU
« Reply #120 on: June 04, 2016, 04:40:49 pm »
I just received a "refurbished" KA3305D from SRA. Their tech said that any returns for whatever reason are thoroughly tested before being resold, so of course I expected everything to work. But unfortunately that wasn't the case. On Ch3's 5V fixed terminal I only get a few mv output. Any suggestions before I call their tech support Monday? Thanks.
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #121 on: June 04, 2016, 04:46:41 pm »
I just received a "refurbished" KA3305D from SRA. Their tech said that any returns for whatever reason are thoroughly tested before being resold, so of course I expected everything to work. But unfortunately that wasn't the case. On Ch3's 5V fixed terminal I only get a few mv output. Any suggestions before I call their tech support Monday? Thanks.

It may be a stupid suggestion, but are you measuring between the + and - and not the - and the GND?

:D
 

Offline YottaByte

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Re: Inside the new Korad KA3305P linear PSU
« Reply #122 on: June 04, 2016, 04:57:27 pm »
SantaClaw,
Thanks for the quick response! No such thing as a stupid question. The mv output is between the + and - terminals. I haven't opened the case to check inside. Just disappointed, especially after talking to the tech who confirmed that refurbished units were thoroughly tested. BTW, the PS looks brand new, only the user's manual was photocopied.
 

Offline SantaClaw

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Re: Inside the new Korad KA3305P linear PSU
« Reply #123 on: June 04, 2016, 05:01:18 pm »
Yeah, well, then I'm out of suggestions, I just measured mine, it's pinned at 4.98v, if I set the two other channels to 5.00v they measure at 4.99v, but that could be my meter as well...

 

Offline YottaByte

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Re: Inside the new Korad KA3305P linear PSU
« Reply #124 on: June 04, 2016, 05:37:27 pm »
Thanks, I'll just have to wait until Monday to call them.
 


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