Building an Unregulated Linear Power Supply

[elan120]

After reading about Nenon's design Unregulated Linear Power Supply (ULPS) back in May, I got very interested, but work schedule got in the way, and I had to wait until now to build it.  This thread, once again, is a continuation of my previous power supply build, and hopefully, it has enough details to help inspire more people to build one.

 

As many of you already know, this ULPS is intended to use with Taiko Audio DC-ATX power supply.  The original post from Nenon is here, and the more recent update as well as the wiring diagram (shown below) is here.

 

Since this is a DIY power supply, my build is one of many different ways to do, and you should review as many builds before this one to gain more ideas.

 

This build is the V3 version.  I do have some deviations from the original design, although the changes are considered as minor, I will list them here in case anyone is curious.

• Add a switch to use with soft start.
• Use bus bar as well as thicker gauge wire.

 

My first step is always try put together a layout with all key components, and this is no different.  After few nights of maybe 7 to 10 different layouts, I decided to go with this one below.

 

 

 

Once I have the layout decided, my build plan is going from power input to power output, and the next step is to get the sheet metal work done.  The first sheet metal work is getting the transformer base plate mounting screw holes drilled.

 

Transformer mounting holes drilled and standoff installed:

 

 

The soft start is placed on the side panel, and two additional holes need to be drilled and tapped to mount the soft start module.

 

Side panel with standoff installed:

 

 

The soft start module have different configuration options available, and the detail can be downloaded from here.  In my case, I need to configure it to run 115VAC, and I will use a power switch.

 

My connection preference is soldering, to make the soldering easier, I removed the edge connectors came with the module and solder the input voltage jumpers, switch and IEC power input wires.

 

Stock soft start module:

 

 

Soft start module with edge connectors removed:

 

 

Soft start with 115VAC jumper wires soldered:

 

 

Soft start with power switch and IEC input AC wires soldered:

 

 

I then installed the damping sheet to the side panel as well as the rear panel before mounting the soft start module, power switch, IEC entry module, and output connector.

 

Side panel with damping sheet installed:

 

 

Rear panel with damping sheet and components installed:

 

 

Once I have both side and rear panels installed, I mount the transformer to the standoffs installed earlier, cut all the wires to proper length and solder them together.  As a safety precaution, I also wired one ground wire to the bottom of the inner plate.

 

Input wiring completed:

 

Ground wire to chassis:

 

 

After having all input power wiring done, it is a good time to run a quick power test to check if everything is wired correctly.  Please note, the switch option on soft start module is acting opposite of what a power switch would do normally, where switch in closed position will place soft start in standby mode (no power), when switch in opened position will place soft start in power-on mode.  In my case, since I only have normally open switch on the bench, I had to turn the "O" marking to the top.  If you don't have a switch already, get a normally closed switch instead.

 

My power test ran good, with power on, it is showing 25.4VAC, and after few on-off cycles with no issues, it is time to move to the next stage by cutting the bus bar needed.

 

Dry fit the 5 caps and getting the bus bars prepared:

 

 

 

 

With the bus bars done, I soldered the first choke (inductor), Saligny rectifier, and VCAP to the first Mundorf (22,000uF) cap.  Please note, VCAPs use solid-core copper leads. Because of the nature of solid core copper, extra care should be exercised when bending the leads for installation.  A gentle radius bend is better than an acute bend.  Leads should be kept as short as possible.  Be very careful when soldering, don't apply heat to the solder joint for a lengthy period of time. This may result in excessive heat buildup, and compromise the electrical connection of the lead to the cap winding, or compromise the hermetic seal.  Although the VCAPs are not polarized, but it is best to keep the lead orientation relative to the innermost and outermost foil consistent where the short lead indicates the outermost foil, and should be connected to the lowest impedance path to ground.  The ODAM capacitors have metal bodies that are electrically conductive.  Ensure that the body doesn't make electrical contact with any other portion of the circuit.
 

Completed first cap:

 

 

After having the first cap done, it is a good time to run another quick power test to check if rectifier is working properly.  My power test show 36.2VDC output, it is working per design.

 

Next step is to install the second choke, solder the wires and VCAP to the second Mundorf (22,000uF) cap.

 

Completed second cap:

 

 

 

Once the second cap wiring is done, time to move on to solder the output wires, here I use 11 gauge solid core copper wire, and I also soldered a 6 gauge solid core copper wire to link between the 22,000uF Mundorf cap and the 47,000uF Mundorf cap.

 

Ground link between 22,000uF and the 47,000uF Mundorf cap, and output wiring completed:

 

 

That was the final soldering for this power supply.  The remaining two VCAPs were screwed down to the 47,000uF Mundorf cap.  Please note, all ring terminal connectors used in this build are Mundorf Mconnect CLG Cable Lugs.
 

Finished power supply:

 

 

 

 

 

 

 

This was another enjoyable build, and I hope there are enough details for you to build yours.  Thank you for reading.

 

 

 

 

[Exocer]

@elan120 you’ve done it again!

I now need to rebuild, taking a few queues from your tremendously neat layout. 
 

Thank you for sharing!

-Rob

[R1200CL]

Send it to ASR for measurements 😂

 

May I ask how much spent in parts ?

[oneguy]

As soon as a fatten up my wallet from my server build this is next on my list. Thanks @elan120!

[Tatomek7]

as usual, very neat and inspiring work. Thank you

 

[Patatorz]

Thanks a lot for this very precise and inspiring post. Still thinking if i will follow you but clearly it helps me to move forward 😄

[Exocer]

@elan120 you have quite a lot of experience with TOTL power supplies. Have you had a chance to hear this one? Any thoughts/impressions/comparisons you can share with us?

 

Cheers

[elan120]

@Exocer, Yes, but not much during this holiday season.  Initial impression is very good, but I still need to make up the right cable as well as lots of burn-in to provide a better comparison between what I use now versus this one.  I do think, based on limited listening, this could end up be my long term reference.  I am planning to use this power supply for my next server build, it is still in parts gathering stage, and I hope to have it started around early Feb-2022.

[dminches]

@elan120, why did you opt for copper bars instead of wire?  Also, where did you get the copper?

[One and a half]

26 minutes ago, dminches said:

@elan120, why did you opt for copper bars instead of wire?  Also, where did you get the copper?

Copper bar in hobbyist lengths are from McMaster Carr. 

 

Copper is easier to connect on to large caps, rather than lugs and wires, makes for a neater install.

Although not necessary for low swinging current DC rails, to keep inductance low,  use Copper or tin sheets with insulation. This technique is used in VSD where there's a high rate of didt in the bus bars. Any amount of inductance makes a resonant circuit, but we are talking hundreds of Amps here .

[elan120]

40 minutes ago, dminches said:

@elan120, why did you opt for copper bars instead of wire?  Also, where did you get the copper?

In addition to what @One and a half mentioned, it also lowers the output resistance, which is part of the original design requirement.

[dminches]

11 hours ago, elan120 said:

In addition to what @One and a half mentioned, it also lowers the output resistance, which is part of the original design requirement.

 

Thanks.  Which width and thickness did you use?

 

[oneguy]

12 hours ago, dminches said:

@elan120, why did you opt for copper bars instead of wire?  Also, where did you get the copper?

I haven’t built this power supply yet but you can also get copper bar here:

 

https://www.onlinemetals.com/en/buy/copper-rectangle-bar

 

I used bad stock from them in a kit car fuse box and it worked well. 

[RickyV]

Why not use multiple runs of Mundorf copper or even silver/gold foil?

Well you have to cut it to size because it’s probably to wide.

[elan120]

3 hours ago, dminches said:

 

Thanks.  Which width and thickness did you use?

 

The one showing in the build has Thickness: 0.125" and Width: 0.5".

 

I purchased the bar from the same place @oneguy suggest, and is working very nicely.

 

1 hour ago, RickyV said:

Why not use multiple runs of Mundorf copper or even silver/gold foil?

That is also possible, but I was also trying to reduce the amount of joints, although not sure the difference in resistance, which could be interesting to test and compare.

[NewOldman]

buy one of these,
Coil BL140 AirCore | Mundorf EB GmbH
and wind off some good length and use,

you cant get much better copper

[MarcelNL]

I'm using Neotech UP OCC for the PSU, where possible keeping the wire uncut by removing the insulation and folding it back upon itself.

(My Common Mode choke circuit makes for shorter single runs anyway)

[rico25]

Hello everybody :)
here is the project that I intend to carry out, with a Noratel/Taiko transformer (thanks to Nenon)

 

[bit01]

There are some missing components in your picture @rico25- don't forget the TAIKO is fed DC and will likely have 'noise feeding  back'.

You could list all the parts in the supply (including the rectifier, bypass caps etc and the MB/CPU /cards  you intend to use for better feedback from others (assuming that is what you seek)?

 

ATB

b.

[rico25]

Thank you for your comments Bit01,

yes it is only for layout and size, the set is fiting "Nenon V3" including Saligny rectifier and Vcap Odam

I'll show you the whole thing when it's finished 🙂

[oneguy]

Here’s a scale drawing I did for my planned ULPS build in a H5 case. I don’t have the funds yet for all the components but I figured someone else may want the inspiration. It’s to scale except for the hole (wide enough to drop 6-pin connectors through). 
 

Notes:

-Transformer is sized for Noratel transformer

-VCAPs not depicted but they will go on top of Mundorfs

-Heavy black lines will be copper plates to partition the different stages (power conversion/rectification, capacitor, and DC-ATX)

-Five 6-pin (four for the ATX and one for the CPU) connectors will come out the top of the lower H5 case (server)and plug directly into the Taiko. Short routing and no connectors to worry about. 

[bit01]

@oneguyDo you plan to fasten or brace the cases together in some way or is one simply sitting (with its feet) on top of the other?

[Exocer]

On 12/24/2021 at 6:52 PM, elan120 said:

@Exocer, Yes, but not much during this holiday season.  Initial impression is very good, but I still need to make up the right cable as well as lots of burn-in to provide a better comparison between what I use now versus this one.  I do think, based on limited listening, this could end up be my long term reference.  I am planning to use this power supply for my next server build, it is still in parts gathering stage, and I hope to have it started around early Feb-2022.

@elan120 it is now early February. Do you have any interesting updates for us?

 

Also,do you plan to pick up the recently available Noratel transformer?

 

I have replaced my Toroidy with the Noratel but made some other changes in my chain that make a direct comparison impossible. What I will say is my system sounds the best it has ever sounded. Although the Toroidy was no slouch.

 

-Rob

[oneguy]

For those in North America, it’s cheaper to order the Mundorf capacitors, Hypex soft start, and Furutech IEC from https://www.audiophonics.fr/en/ than using parts http://partsconnexion.com

 

$700 with shipping from Audiophonics vs $930 from partsconnexion and that doesn’t include shipping or the soft start.

 

In fact, you can even add in the slimline case like modushop sells and the perforated case bottom and it’s still only $875 with shipping from Audiophonics. 
 

Pretty big savings.

 

On the subject of savings, it’s $43 for shipping for the Saligny rectifier which cost $44. The shipping is flat no matter how many you order. I can place a large order so we save on shipping then mail them out to people individually. If anyone wants to jump in just shoot me a PM by Feb 25th

 

Costs below include USPS priority mail to from me to you. 

[oneguy]

10 minutes ago, bit01 said:

@oneguyDo you plan to fasten or brace the cases together in some way or is one simply sitting (with its feet) on top of the other?

When I was planning on putting the Taiko in the server chassis I was going to use and XLR connection to link the two (one on the top of the server and one on the bottom of the ULPS) which would have required precise mating and a guide. The method I described in my previous post wouldn’t require precise mating and unless there was an earthquake they would slide in relation to each other so no bracing is required.

 

It can certainly be added though

-Spiked feet isolators

-A cup and ball type system

-guiding rod and cylinder