cheap/chinese LPSU's - minefield?

[sandyk]

 

the_doc735

You need to specify the output voltages and currents required, as well as the price range.

Also, whether they are needed for applications where very low noise is required, or just for areas where you wish to replace an existing SMPS plugpack where the requirements are more relaxed and a cheaper LPSU will be adequate..

[sandyk]

I also use the internal 650W SMPS in my PC, but use additional voltage regulation to provide cleaner power to several of the internal SATA devices.(Optical device and 2 SATA SSDs)   My PC is also powered via a substantial DIY A.C. Filter board to further reduce crap going back into the A.C. mains supply.

I don't believe in using numerous additional Linear PSUs to provide power for internal devices due to the need to avoid Earth Loops for best results.

 You can't always directly hear the effects of earth loops, such as mains frequency related hum, bur they do cause degradation.

 

IIRC, Jon prefers to clean up any residual noise problems using S.O.A. Optical fibre cable distribution.

[sandyk]

2 hours ago, the_doc735 said:

"a substantial DIY A.C. Filter board to further reduce crap going back into the A.C. mains". Please tell me more with pics. please?

"S.O.A. Optical fibre cable distribution". Please elaborate? thank you!

I don't have optical devices in PC OR SSD's; only M.2 NVMe storage card.

"I also use the internal 650W SMPS in my PC," - WOW!! - so this is 'the other side of the coin'?

"I don't believe in using numerous additional Linear PSUs to provide power for internal devices due to the need to avoid Earth Loops". So, you don't believe in using four LPSU's for the mobo (12v CPU/ATX 12v/5v/3.3v)?

The DIY mains filter that I used is no longer obtainable on ebay. It required assembly (soldering) and I also added a few varistors for added protection against mains voltage spikes , and  put it in a plastic case with a couple of mains sockets mounted on top.

 

Ask Jon what he uses to clean up and distribute the signal. He uses Pro type Optical gear to do that.

I prefer to do the cleaning up to improve Signal Integrity before it leaves the computer.

There is more than one way to " skin a cat ".

 

No, I don't believe in using four LPSU's for the mobo (12v CPU/ATX 12v/5v/3.3v)?

 OTOH, if they were all in the same case and well isolated from each other electrically (e.g. separate transformers)

that could be a different matter, but perhaps well and truly overkill ?

 

[sandyk]

31 minutes ago, the_doc735 said:

https://www.ebay.co.uk/itm/Finished-4-way-High-Current-Hifi-linear-Power-supply-DC5V-9V-12V-19V-LPS-L4-21/123099825369?hash=item1ca95244d9:g:gGIAAOSwaZFa4KhG

 

https://www.ebay.co.uk/itm/HIFI-3-way-linear-power-supply-DC5V-3A-DC9V-2-5A-DC12V-2-5A-L6-38/123203794481?hash=item1caf84b631:g:D8AAAOSwcSJa8xMw

 

Neither of these supplies have a 3.3V output as you specified.

[sandyk]

9 hours ago, barrows said:

As to the use of counterfeit parts in China I have direct experience of it, it is commonplace and well known in the industry.

 

Several members of a U.K. based forum who were constructing my Class A Preamplifier design were caught out by counterfeit Toshiba 2SC5171 transistors with very low HFE and a slightly different looking logo supplied by a major U.K. distributor, who to their credit quickly withdrew them from sale.

[sandyk]

17 minutes ago, rickca said:

I'll leave  it to you to pursue if you think it's warranted.  I don't plan to buy these products.  Maybe some of the other contributors to this thread can comment on whether the design could reasonably be expected to deliver max ripple of 25uV.

 It is achievable using this quoted technology :

Quote

Using precision voltage reference + high speed op amp + MOS output power Transistor

 

Whether it is or not is a different matter, and may be from the specifications quoted for a design based on this topology.

[sandyk]

 

 

Quote

      43 minutes ago, 4est said:

Once again, you do not know enough to know what you don't know. Worse, you are expecting people to spoon feed you all of this...

 

 

that really helps.

This kind of advice may just save your life, or that of a family member. 

We haven't even got into the area of wiring in a suitably rated fuse(s) which could help prevent a fire in the event of a fault condition, or correct earthing where a 3pin mains plug is used, proper insulation standards where the PSU isn't earthed, suitable gauge wire for internal cabling AND appropriate colour of the cabling used to help prevent costly errors when wiring it up. Then there are proper Earthing techniques .(below)

I bet that you didn't know for example that some IEC sockets have a metal strip which is at full A/C mains potential !

 

[sandyk]

9 hours ago, the_doc735 said:

Please see my reply to @Superdad  above (4 posts back) for area's that I need help with!

e.g. what is a suitable tranny for,four of these boards?

cheers!

 

 How much experience do you have using a soldering iron with electronic components, and using a DMM for continuity and voltage testing etc.?

 Do you own a DMM ?

Your questions so far suggest that you are well out of your depth with the construction of a multi supply rail higher power PSU.

 Nobody is laughing at you as we all had to start somewhere, which was with much simpler projects than this very ambitious one..

[sandyk]

 

 

Quote

...maybe he knows the input voltage?

The Input voltage will of course depend on the chosen Output Voltage, which also means that the transformer as well will need to be selected to provide adequate, but not too much headroom for the selected output voltage.

 You will need to ask these questions of the vendor when selecting the voltage version and current required.

[sandyk]

3 hours ago, davide256 said:

I have one of those cheap chinese LPS's, works ok as an upgrade for my turntables 24vDC transformer. But the voltage does drift  up to .5V higher and it becomes unstable

if you turn the voltage adjustment screw below 12V...

 

Any LPS whose output voltage drifts by 500mV is NOT well designed.

A typical drift with temperature and load conditions should be more like 10% (or less) of that.(< + and - 50mV)

 The output voltage of most voltage regulators increases a little with increasing temperature, and the output voltage droops a little with higher current loads.

[sandyk]

2 hours ago, the_doc735 said:

Interestingly just got a reply from the LPSU board supplier in china and UNLIKE the tranny supplier has offered to help a little bit with voltage input. He mentions the same issues as @jabbr  and @Superdad  and @sandyk 

 

Among the other unanswered questions that really need to be known, is how much is the required minimum voltage differential between the Input and Output voltages. This particular PSU PCB design is not like when using a quoted type voltage regulator I.C.  (LM3xx , or a L.D.O type etc.) where we know the minimum voltage differential for proper regulation.

You also need to know the amount of maximum current as well as the rectified voltage from the transformer you will be using to determine the heat sinking requirements from the amount of heat to be dissipated.

( My 15W Ch. Class A amplifier for example, dissipates a total of over 80W [P =E x I ] of heat and requires a 300mm x 75mm x 49mm (W x H x D) heatsink on either side of the 2U rack case for safe operation in the hotter months.)

 Obviously, the higher the Input -Output voltage differential and the high current that this PSU PCB is capable of will determine the amount of heat sinking required.

 You would more than likely be using a Bridge Rectifier configuration, and the attached chart will assist with working out the voltages to be expected from a particular transformer and rectifier combination with a large value filter capacitor.

[sandyk]

Doc

 Too many novice type questions are putting off many members from further replying.

 You need to do a little more reading yourself on the plus and minus aspects for both types of supplies.

 You will find plenty of discussions in other areas of the forum, especially the Uptone area with John Swenson.

 

Please check your PMs

Alex