Author Topic: New Bench Power Supply - Chinese  (Read 9332 times)

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Offline DW1961Topic starter

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New Bench Power Supply - Chinese
« on: October 25, 2021, 04:29:13 am »
Well, I received a 30V 10A power supply back a while ago, and posted up here. A couple of days ago, I received another Chinese bench power supply operating at 30 5A. I requested it because it was a LOT smaller than the 10A unit, and since I will infrequently use 10A, I thought I would replace the 10A unit with the smaller 5A unit, and save some space on my bench.

Anyway, I wanted to toss up some images and see what the community thinks. One thing I would like to ask is that this unit has a 120/240 switch on the back. How does that switch work? If I leave it at 240, will it work on 120V power mains? I've just never thought about it before, and most modern supplies convert automatically (if they convert at all).


Link: https://www.amazon.com/dp/B09CGWG4GP
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For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.
« Last Edit: October 25, 2021, 04:35:52 am by DW1961 »
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #1 on: October 25, 2021, 04:33:53 am »
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Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #2 on: October 25, 2021, 04:34:34 am »
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Offline MarkF

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Re: New Bench Power Supply - Chinese
« Reply #3 on: October 25, 2021, 07:09:27 am »
. . .
For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.

There is absolutely NO REASON to upload a 5 MB image to the forum!   :box:
I don't need to watch fleas running underneath SMD resistors.
There is a thread somewhere about how big images should be.  I haven't followed it to its end.
But, images that size SHOULD be scaled down before posting.  IMHO.

My 'dark' theme for the forum limits the display of images to my screen size (i.e. 1080p).
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« Last Edit: October 25, 2021, 07:12:42 am by MarkF »
 
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Re: New Bench Power Supply - Chinese
« Reply #4 on: October 25, 2021, 07:13:44 am »
. . .
For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.

There is absolutely NO REASON to upload a 5 MB image to the forum!   :box:
I don't need to watch fleas running underneath SMD resistors.
There is a thread somewhere about how big images should be.  I haven't followed it to its end.
But, images that size SHOULD be scaled down before posting.  IMHO.
I very much agree. 200-500KB images are plenty large enough excepting when the finest detail is required.

Clearly listed on the posting page in the Attachments and other options section:
Restrictions: 10 per post, maximum total size 5000KB, maximum individual size 4000KB
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Offline radiolistener

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Re: New Bench Power Supply - Chinese
« Reply #5 on: October 25, 2021, 07:38:46 am »
There is no reason to buy such PSU. First of all, this is switching power supply, and this means that it's output is very noisy, it produces high EM interference for nearby equipment. And it's max current is just 10 Amps which is almost the same as for popular linear PSU with 5-10 Amps. In addition this is a cheap Chinese switching mode PSU, which means that it is even more noisy than branded PSU, it produce more EM interferences, has unstable output and is not reliable. This is just a noisy kids toy.

And after all, such cheap switching mode PSU may be unsafe for your life and equipment. Because it uses cheap components on a "hot" (high voltage) part of circuit.

So, it's better to buy 10 Amps linear PSU, like KORAD KA3010D.

Switching mode PSU makes sense to buy if you're needs very high current (about 20-100 Amps) for powerful equipment and you are not worried about the level of interference and noise. So, in order to buy switching mode PSU, it needs at least 20-30 Amps output. Otherwise it can be easily replaced with linear PSU which has low noise and don't produce EM interferences.

For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.

There is no sense to upload tens of images with 5 MB each. 600 kB limit is well enough. So large image may have sense if you upload a single image with a high resolution which is needed to see all details. But it have no sense for a usual teardown pictures.

There is no sense to see the dust particles shape on the table near PSU :)
« Last Edit: October 25, 2021, 07:54:57 am by radiolistener »
 
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Offline J-R

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Re: New Bench Power Supply - Chinese
« Reply #6 on: October 25, 2021, 08:52:22 am »
- Sure, no need for such large photos.  But also no need for the attitude from the forum veterans.  Just ask the OP to please replace the photos with smaller ones?
- I can't remember the last time I saw a consumer device with a linear power supply, they are all switching.  So it might be of use for some purposes.  (But yes, linear is still better for the electronics bench.)
- That Korad might be a linear supply, but other than some credibility it has earned here on the forums is still just a cheap PSU that could also be dangerous.  It had many faults when it first came out.

- I would be pretty confident in saying the switch on the back should be set to 120V if that is what you're feeding it.
- Can't tell exactly from the photos but the power switch wiring and the grounding looks a little suspect.  Better check it out.
- What is "programmable" about this?  Do you plug in to the USB port on the front or something?
 
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Offline Gyro

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Re: New Bench Power Supply - Chinese
« Reply #7 on: October 25, 2021, 09:05:31 am »
If you're posting a thread like this, then you should be posting traces of output performance - turn on / off and load change transient behaviour, ripple and noise etc.

A few oversized internal photos really don't tell you anything much (apart from grounding) about the desirability of the supply for actual use.
Best Regards, Chris
 
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Offline radiolistener

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Re: New Bench Power Supply - Chinese
« Reply #8 on: October 25, 2021, 10:22:06 am »
- I can't remember the last time I saw a consumer device with a linear power supply, they are all switching.  So it might be of use for some purposes.  (But yes, linear is still better for the electronics bench.)

Lab power supply is not usual consumer device, it should produce clean and stable voltage for different purposes. You're needs to believe that it has clean output with no issues. With no needs to guess a riddle what is the source of that noise and why there a strange pulses... So, switching PSU is a bad choice. And if it's cheap Chinese switching PSU it is even worse..
« Last Edit: October 25, 2021, 10:24:12 am by radiolistener »
 
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Offline RoGeorge

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Re: New Bench Power Supply - Chinese
« Reply #9 on: October 25, 2021, 10:34:24 am »
One thing I would like to ask is that this unit has a 120/240 switch on the back. How does that switch work? If I leave it at 240, will it work on 120V power mains? I've just never thought about it before, and most modern supplies convert automatically (if they convert at all).

If your power supply has a switch to choose between 110 or 220Vac for mains, then you must put it in the correct position.  Read the manual to double check which position is for each mains voltage level.  Most of the switching power supplies can work on either voltage, but not all of them.  If there is a switch, it means it must be set according to the mains voltage.
-  If your mains is 240Vac and the switch is set for 120Vac, the source will get damaged, or even start a fire.
-  If your mains is 120Vac and the switch is set for 240Vac, it won't work correctly

Offline Yansi

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Re: New Bench Power Supply - Chinese
« Reply #10 on: October 25, 2021, 12:09:53 pm »
the switch bridges half of the mains bridge rectifier with the midpoint of the two filtering caps, to form a voltage doubler.

For 230V input, it works as a normal bridge rectifier, obtaining about 330Vdc at the capacitors.
At 115V position, it makes it a voltage doubler, providing the same 330Vdc at the cap outputs.
 
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Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #11 on: October 25, 2021, 04:40:34 pm »
. . .
For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.

There is absolutely NO REASON to upload a 5 MB image to the forum!   :box:
I don't need to watch fleas running underneath SMD resistors.
There is a thread somewhere about how big images should be.  I haven't followed it to its end.
But, images that size SHOULD be scaled down before posting.  IMHO.
I very much agree. 200-500KB images are plenty large enough excepting when the finest detail is required.

Clearly listed on the posting page in the Attachments and other options section:
Restrictions: 10 per post, maximum total size 5000KB, maximum individual size 4000KB

And there you go! The problem is that if you compress down past about 50% for a JPG, you start to get bad artifacts and pixeling. I set it to 65% and the files recompressed to 1.4MB each.
 

Offline Gyro

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Re: New Bench Power Supply - Chinese
« Reply #12 on: October 25, 2021, 04:51:42 pm »
It sounds as if you're using the wrong tool - try Resize. It's as old as the hills and standalone, but I use it to do major image compressions (~6MB down to a couple of hundred kB) with very little perceptible quality reduction...

https://resize.en.uptodown.com/windows


Edit: Eg, This one... 6MB down to 116kB.

https://www.eevblog.com/forum/projects/resistor-extreme-pulse-overload-experiments/?action=dlattach;attach=372530;image
« Last Edit: October 25, 2021, 04:59:42 pm by Gyro »
Best Regards, Chris
 
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Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #13 on: October 25, 2021, 05:02:38 pm »
There is no reason to buy such PSU. First of all, this is switching power supply, and this means that it's output is very noisy, it produces high EM interference for nearby equipment. And it's max current is just 10 Amps which is almost the same as for popular linear PSU with 5-10 Amps. In addition this is a cheap Chinese switching mode PSU, which means that it is even more noisy than branded PSU, it produce more EM interferences, has unstable output and is not reliable. This is just a noisy kids toy.

And after all, such cheap switching mode PSU may be unsafe for your life and equipment. Because it uses cheap components on a "hot" (high voltage) part of circuit.

So, it's better to buy 10 Amps linear PSU, like KORAD KA3010D.

Switching mode PSU makes sense to buy if you're needs very high current (about 20-100 Amps) for powerful equipment and you are not worried about the level of interference and noise. So, in order to buy switching mode PSU, it needs at least 20-30 Amps output. Otherwise it can be easily replaced with linear PSU which has low noise and don't produce EM interferences.

For some reason I had to limit my images to 5000kb, which is about 3 images per post. Sorry for the multiple replies, but it was the only way to get the images uploaded.

There is no sense to upload tens of images with 5 MB each. 600 kB limit is well enough. So large image may have sense if you upload a single image with a high resolution which is needed to see all details. But it have no sense for a usual teardown pictures.

There is no sense to see the dust particles shape on the table near PSU :)

I don't buy them. I receive them for free for doing a basic review of the products.

You mean all switching power supplies are necessarily RF noisy, like my computer power supply (that isn't at all)?
« Last Edit: October 25, 2021, 05:25:24 pm by DW1961 »
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #14 on: October 25, 2021, 05:06:01 pm »
- Sure, no need for such large photos.  But also no need for the attitude from the forum veterans.  Just ask the OP to please replace the photos with smaller ones?
- I can't remember the last time I saw a consumer device with a linear power supply, they are all switching.  So it might be of use for some purposes.  (But yes, linear is still better for the electronics bench.)
- That Korad might be a linear supply, but other than some credibility it has earned here on the forums is still just a cheap PSU that could also be dangerous.  It had many faults when it first came out.

- I would be pretty confident in saying the switch on the back should be set to 120V if that is what you're feeding it.
- Can't tell exactly from the photos but the power switch wiring and the grounding looks a little suspect.  Better check it out.
- What is "programmable" about this?  Do you plug in to the USB port on the front or something?

Hey JR thanks for your comment. As already stated, i did reduce the files to 1.4MB but I was unaware that total files cannot exceed 5MB.

Anyway, on one of the PSU, not this one, you can plug it into your computer and do some stuff with it using software.

I will retake some pictures of the power switch so you can better comment on it.
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #15 on: October 25, 2021, 05:10:15 pm »
If you're posting a thread like this, then you should be posting traces of output performance - turn on / off and load change transient behaviour, ripple and noise etc.

A few oversized internal photos really don't tell you anything much (apart from grounding) about the desirability of the supply for actual use.

It can tell you how well they have use RFI and other filters and capacitors, grounding, etc. though.  Of course, the end result is a scope. I don't have a scope so I can't measure the output power cleanliness and efficiency of the unit. I was just wondering if even the unit is electronically or mechanically sound. I only saw one coil choke on it, for instance.
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #16 on: October 25, 2021, 05:12:47 pm »
the switch bridges half of the mains bridge rectifier with the midpoint of the two filtering caps, to form a voltage doubler.

For 230V input, it works as a normal bridge rectifier, obtaining about 330Vdc at the capacitors.
At 115V position, it makes it a voltage doubler, providing the same 330Vdc at the cap outputs.

Why would you need to double 120V with a 30V power supply?
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #17 on: October 25, 2021, 05:16:44 pm »
- I can't remember the last time I saw a consumer device with a linear power supply, they are all switching.  So it might be of use for some purposes.  (But yes, linear is still better for the electronics bench.)

Lab power supply is not usual consumer device, it should produce clean and stable voltage for different purposes. You're needs to believe that it has clean output with no issues. With no needs to guess a riddle what is the source of that noise and why there a strange pulses... So, switching PSU is a bad choice. And if it's cheap Chinese switching PSU it is even worse..

Radio, have you ever seen the output on  a scope for a higher end computer power supply? They are far from dirty and unstable and their RFI is near zero.
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #18 on: October 25, 2021, 05:24:22 pm »
It sounds as if you're using the wrong tool - try Resize. It's as old as the hills and standalone, but I use it to do major image compressions (~6MB down to a couple of hundred kB) with very little perceptible quality reduction...

https://resize.en.uptodown.com/windows


Edit: Eg, This one... 6MB down to 116kB.

https://www.eevblog.com/forum/projects/resistor-extreme-pulse-overload-experiments/?action=dlattach;attach=372530;image

My error. Just tested it and my compression program will compress it way down past 62% with good results. I got it down to 432KB and can probably go even lower. Completely acceptable quality for the forum. Thanks.
 

Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #19 on: October 25, 2021, 05:26:56 pm »
Just wanted to say this isn't a thread for switching vs linear arguments.

I was just simply looking for opinions on the hardware they used, wiring, filters, etc.
 

Offline Gyro

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Re: New Bench Power Supply - Chinese
« Reply #20 on: October 25, 2021, 05:33:55 pm »
If you're posting a thread like this, then you should be posting traces of output performance - turn on / off and load change transient behaviour, ripple and noise etc.

A few oversized internal photos really don't tell you anything much (apart from grounding) about the desirability of the supply for actual use.

It can tell you how well they have use RFI and other filters and capacitors, grounding, etc. though.  Of course, the end result is a scope. I don't have a scope so I can't measure the output power cleanliness and efficiency of the unit. I was just wondering if even the unit is electronically or mechanically sound. I only saw one coil choke on it, for instance.

Unfortunately not. A really detailed analysis of the PCB layout (and schematic) might give a clue, but the effort would be considerable, for an experienced designer, and you wouldn't really have confidence in this without actual measurements. It depends on things like the internal construction quality of the magnetics etc, which are invisible.
« Last Edit: October 25, 2021, 05:36:13 pm by Gyro »
Best Regards, Chris
 

Offline radiolistener

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Re: New Bench Power Supply - Chinese
« Reply #21 on: October 25, 2021, 05:39:05 pm »
You mean all switching power supplies are necessarily RF noisy, like my computer power supply (that isn't at all)?

Yes, all switching mode PSU have noise on the output and produce EM interference. Good branded switching mode PSU has a good filters, shielding, bypass-capacitors through shielding for enter and exit wires and is designed in such way to minimize these issues. Cheap Chinese PSU don't have it at all and is noisy like hell.

Radio, have you ever seen the output on  a scope for a higher end computer power supply? They are far from dirty and unstable and their RFI is near zero.

yes, it's output is very-very noisy. As I remember it has noise with up to 0.5 V peak pulses. And it has RFI, you can listen it on a short wave receiver ;)
« Last Edit: October 25, 2021, 05:47:38 pm by radiolistener »
 
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Offline AVGresponding

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Re: New Bench Power Supply - Chinese
« Reply #22 on: October 25, 2021, 06:27:29 pm »
It's a good idea to check the security of all the connections in these, particularly the mains ones, they are not infrequently dangerously loose. Also the one I have (but never use, since it destroys its own display, faulty LED driver IC probably) had not only loosely terminated mains cabling, but some of the semis weren't screwed back tightly to their heatsinks. Remedying this cured a certain amount of audible noise at higher loads...

Now, this isn't from the same manufacturer as mine, or the self-igniting one that Big Clive looked at, but it's worth bearing in mind it'll be designed and built with much the same philosophy and methodology; pare back the costs by using the cheapest possible components (both electrical and mechanical) and assembled by horribly underpaid and overworked unskilled labour.

TLDR; I wouldn't leave it running unsupervised, or powering anything I would be upset to lose.
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Offline DW1961Topic starter

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Re: New Bench Power Supply - Chinese
« Reply #23 on: October 26, 2021, 01:54:22 am »
You mean all switching power supplies are necessarily RF noisy, like my computer power supply (that isn't at all)?

Yes, all switching mode PSU have noise on the output and produce EM interference. Good branded switching mode PSU has a good filters, shielding, bypass-capacitors through shielding for enter and exit wires and is designed in such way to minimize these issues. Cheap Chinese PSU don't have it at all and is noisy like hell.

Radio, have you ever seen the output on  a scope for a higher end computer power supply? They are far from dirty and unstable and their RFI is near zero.

yes, it's output is very-very noisy. As I remember it has noise with up to 0.5 V peak pulses. And it has RFI, you can listen it on a short wave receiver ;)

Well, ok, so you would call this power supply noisy?
https://www.tomshardware.com/reviews/corsair-rm850x-2021-power-supply-review/4
 

Offline radiolistener

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Re: New Bench Power Supply - Chinese
« Reply #24 on: October 26, 2021, 03:58:57 am »
Well, ok, so you would call this power supply noisy?
https://www.tomshardware.com/reviews/corsair-rm850x-2021-power-supply-review/4

Yes, they all are noisy.
I don't have exactly this model for testing, but I have Corsair HX620W. Just measured it, here is it's output noise:


For comparison, here is linear lab PSU KORAD KA3005D:

 
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