Is my lab PSU faulty or is it just crap?

[Francesc V.]

Hi:

I bought it long time ago this Wanptek KPS3010D SMPS.

I would like to use it for injecting Voltage into any circuit, but not sure whether is designed for this purpouse.

This is the sequence I am following:

1. I start shortening the probes and setting 250mA
2. Then I set Voltage to 6V without any load.
3. I connect load..........and voltage drops to 4.1V !!!

(For this testing I know the load consumes 120mA)......

I don't see how I am supposed to use it for injecting load if it does whatever it likes....

Thanks for any feedback,
Francesc.

[sam_sam_sam]

Re: Is my lab PSU faulty or is it just crap?

Here is something to try get an automotive headlight and try to power it up set the voltage at 13.50 volt and turn the current pots all the way to the left and hook up your headlight and slowly increase the current until the light bulb starts glowing and post the results and then both current pots fully to the right and post the results

Then I can tell you if it is working correctly or not

You might have the concept of how to use this type of power supply and how to use it this is the reason for you to do this test the way I describe it above

[eccerr0r]

Re: Is my lab PSU faulty or is it just crap?

TBH something doesn't sound right, however, I don't know where people get the idea of shorting probes to set CC level - though technically is correct, depending on the supply, can cause problems with its sense with real loads.

Agree with sam^3 - you should use something not a computer/digital/semiconductor/nonlinear device to test/experiment with a CCCV PSU. Headlamp works, if you have a few hefty resistors (because they should be linear - incandescent lamps aren't totally linear!), that's better.

[harp]

Re: Is my lab PSU faulty or is it just crap?

Hi:
I would like to use it for injecting Voltage into any circuit, but not sure whether is designed for this purpouse.

From your pictures I dont get it what is wrong, I see that noobs are in different position on each foto, you do 250mA limit and that not conserned if load is lower. Voltage should be the same if current limit not reach, or uncarefuly touched.

For injection, for finding the short on pcb, make shure that psu dont some protection to cutoff output... if is all ok, the wire and clamp has to start heat when short connected and leave that about some time.

[stj]

Re: Is my lab PSU faulty or is it just crap?

if your doing stuff like that, make sure your leads are good - including the joints to the plug/clip

just looking at your picture - what happened to your desoldering station??

[Francesc V.]

Re: Is my lab PSU faulty or is it just crap?

I knew it for sure that it was crap so I disassemble it. Just by visual inspection I realised that the output capacitors were bad. The one from the left had a leakage.

I removed all 4 and they were completely dead. No capacitance at all, and open circuit.



Furthermore, once removed I realised that the one from the left was assembled with wrong polarity!! Maybe the rest died because of this. Now the PSU works as expected without any fluctuation.



I will do the Bulb test and I will post the results :-)

Again this time was because of badcaps and assembly guys that do not pay enough attention

Regards,
Francesc.

P.S: Stj, nothing wrong with my desoldering station, it does magic with multi-layer pcbs

[CapLeaker]

Re: Is my lab PSU faulty or is it just crap?

Well… the wrong polarity thing… manufacturer do make mistakes. Sometimes in the schematic, sometimes in the assembly, sometimes a misprint on the PCB. You have to figure it out if it was actually correct, or indeed wrong way installed. Sometimes it isn’t easy to figure it out, but ran across this before.