Author Topic: Do you have a 30v 5A power supply ?  (Read 901 times)

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Online ThermallyFrigid

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Do you have a 30v 5A power supply ?
« on: July 22, 2021, 09:04:21 pm »
Like this one?.....

If so, with nothing connected......

Condition 1
if you have all 4 knobs turned all the way down (counterclockwise), then turn the Far Right (Voltage Coarse) knob clockwise, ....does the voltage on the meter rise or stay at zero ?


Condition 2
Now....
Turn all 4 knobs back down all the way (counterclockwise)
 Next, turn both the CURRENT knobs clockwise (all the way up)
Finally, turn the FAR RIGHT Voltage Coarse knob Clockwise.......does the voltage on the meter go up as you turn the knob or stay at zero?

« Last Edit: July 22, 2021, 09:09:07 pm by ThermallyFrigid »
 

Offline BeBuLamar

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Re: Do you have a 30v 5A power supply ?
« Reply #1 on: July 22, 2021, 09:55:53 pm »
In both cases the voltage should go up.
 
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Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #2 on: July 22, 2021, 10:13:11 pm »
In both cases the voltage should go up.

You don't happen to have this particular PSU do you?
 

Offline 2N3055

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Re: Do you have a 30v 5A power supply ?
« Reply #3 on: July 22, 2021, 10:13:37 pm »
If you have current limit set to minimum, the zero current, it won't let the voltage rise, regardless of voltage setting...
CC led will be on.

But if you open current knobs just a little, so CC led shuts off, it will let you rise voltage...
It is how it works...

 

Online duckduck

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Re: Do you have a 30v 5A power supply ?
« Reply #4 on: July 22, 2021, 10:27:47 pm »
I don't own one. It is also sold as the Dr. Meter power supply on Amazon. I will point out that this is, as far as I know, at USD57 + tax (delivered), the cheapest linear power supply available new in the USA. I'd be interested in a teardown and review, or at least some nice pictures of the guts. I haven't found a cheaper (delivered) linear power supply even from AliExpress or BangGood.

EDIT:

Doh! Just checked ebay and it's USD48 + tax, delivered. Wow, that's cheap.

https://www.ebay.com/itm/113139856088
« Last Edit: July 22, 2021, 11:01:38 pm by duckduck »
 
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Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #5 on: July 22, 2021, 10:35:52 pm »
I don't own one. It is also sold as the Dr. Meter power supply on Amazon. I will point out that this is, as far as I know, at USD57 + tax (delivered), the cheapest linear power supply available new in the USA. Sorry to hear that it has issues. I'd be interested in a teardown and review, or at least some nice pictures of the guts. I haven't found a cheaper (delivered) linear power supply even from AliExpress or BangGood.

For years it was my only power supply.

Now I have a bench full of better power supplies.   But I still really like this one , for all it's cheapness and faults.
I had blown this one out about 2 months ago by connecting it backwards to a boat battery.   ElectroBOOM style.   Magic Smoke released.

Since then I've repaired all the damage and it's back up and running, but I can't recall the two conditions posted in the OP and wanted someone who actually has the same one to verify.

I have a very extensive cataloging of the components and I'm working on a full schematic in KiCAD.
  Why would I do this for such a cheap power supply?   One word....Learning.
Electronics has become a favorite hobby.

I've repaired 3 blown Meanwell Power supplies, a 58v battery charger, an inverter, a Bissell battery board and a few other fun things.

This one has a fair amount of SMD components on it,  a few that I successfully replaced.

I never knew electronics could be so rewarding and fun.

 

Online TimFox

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Re: Do you have a 30v 5A power supply ?
« Reply #6 on: July 22, 2021, 10:37:31 pm »
With most of my vintage linear bench supplies, with the current knob(s) set fully CCW, the output current is forced to zero.
 

Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #7 on: July 22, 2021, 10:38:51 pm »
If you have current limit set to minimum, the zero current, it won't let the voltage rise, regardless of voltage setting...
CC led will be on.

But if you open current knobs just a little, so CC led shuts off, it will let you rise voltage...
It is how it works...

Good.  Then it seems to be functioning normally, as designed.   Time to reinstall the cover.
 

Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #8 on: July 22, 2021, 10:41:01 pm »
With most of my vintage linear bench supplies, with the current knob(s) set fully CCW, the output current is forced to zero.

Well that makes sense.

But this is really about voltage in this thread and how the PSU responds when voltage adjustments are moved with current is set to OFF and then ON.
« Last Edit: July 22, 2021, 10:48:24 pm by ThermallyFrigid »
 

Offline MAS3

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Re: Do you have a 30v 5A power supply ?
« Reply #9 on: July 22, 2021, 10:42:40 pm »
@duckduck:

Well, this isn't an issue, it's a feature.
As explained by @2N2055: if you set the current limiter to 0.0 A, you'll enable the limiter (and it's indication LED).
That will disable the voltage setting.
Turn up the current to more than 0 A, and you'll be able to set voltage.

The manual should have explained about that too, but like these supplies the manuals aren't the best around.
 

Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #10 on: July 22, 2021, 11:00:11 pm »
@duckduck:

Well, this isn't an issue, it's a feature.
As explained by @2N2055: if you set the current limiter to 0.0 A, you'll enable the limiter (and it's indication LED).
That will disable the voltage setting.
Turn up the current to more than 0 A, and you'll be able to set voltage.

The manual should have explained about that too, but like these supplies the manuals aren't the best around.

Excellent.
It doesn't help much that I'm still an ElectroNOOB
 

Online bdunham7

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Re: Do you have a 30v 5A power supply ?
« Reply #11 on: July 22, 2021, 11:55:33 pm »
  Why would I do this for such a cheap power supply?   One word....Learning.

Well then you should consider why the current control behaves that way.  And perhaps why it was designed that way.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline BeBuLamar

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Re: Do you have a 30v 5A power supply ?
« Reply #12 on: July 23, 2021, 12:29:57 pm »
In both cases the voltage should go up.

You don't happen to have this particular PSU do you?

No! My power supplies are not of the same model but if I connect them to nothing the voltage would rise even if the current limit is set to zero.
 

Offline Circlotron

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Re: Do you have a 30v 5A power supply ?
« Reply #13 on: July 23, 2021, 01:00:32 pm »
I don't own one. It is also sold as the Dr. Meter power supply on Amazon. I will point out that this is, as far as I know, at USD57 + tax (delivered), the cheapest linear power supply available new in the USA. I'd be interested in a teardown and review, or at least some nice pictures of the guts. I haven't found a cheaper (delivered) linear power supply even from AliExpress or BangGood.

Linear??? Mine is switchmode. Do they make a linear version in the same case?
 

Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #14 on: July 24, 2021, 09:30:08 am »
Not as far as I know.

All of these use PWM and are not linear power supplies.
 

Online ThermallyFrigid

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Re: Do you have a 30v 5A power supply ?
« Reply #15 on: July 24, 2021, 09:35:05 am »
In both cases the voltage should go up.

You don't happen to have this particular PSU do you?

No! My power supplies are not of the same model but if I connect them to nothing the voltage would rise even if the current limit is set to zero.

On the one that this thread is about, if connected to nothing, if you turn both Current knobs to zero, the voltage drops to zero.   You have to have some current dialed in to get any voltage.

That said, if you have any power supply that uses analog potentiometers for settings, consider replacing them once every few years (or at least cleaning them well)
I have found that this unit's reliability is totally dependent on the accuracy of the adjusting pots.  Wonky things happen when they lose their accuracy.

You need qty 2, B1K pots and two B10k pots for this unit.  Very easy job.  Buy quality pots.
« Last Edit: July 24, 2021, 09:43:26 am by ThermallyFrigid »
 

Offline antimatter503

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Re: Do you have a 30v 5A power supply ?
« Reply #16 on: July 25, 2021, 04:18:20 pm »
I don't own one. It is also sold as the Dr. Meter power supply on Amazon. I will point out that this is, as far as I know, at USD57 + tax (delivered), the cheapest linear power supply available new in the USA. I'd be interested in a teardown and review, or at least some nice pictures of the guts. I haven't found a cheaper (delivered) linear power supply even from AliExpress or BangGood.

Linear??? Mine is switchmode. Do they make a linear version in the same case?

Yes, they do indeed make a linear version and a switchmode version.
 

Online mawyatt

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Re: Do you have a 30v 5A power supply ?
« Reply #17 on: July 25, 2021, 04:33:16 pm »
We have one of these that's a switcher. It puts out so much switching noise on the output terminals and the mains power to be almost useless for anything other powering a motor or light bulb :P

Tried a few things to help, but gave up.

I wouldn't recommend the switching version, but don't know about the linear version.

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Online AVGresponding

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Re: Do you have a 30v 5A power supply ?
« Reply #18 on: July 25, 2021, 07:22:20 pm »
I have the 10A switcher version, and it is indeed hilariously bad.

Worth checking the semis are properly screwed back to the heatsinks in these, indeed all the screw terminations too. Many in mine were loose, tightening them did reduce the audible noise under load.
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