Replacing / repairing old power supplies & switching from 100V

[pvision]

A fairly large part of what I do revolves around repairing or modifying power supplies in 1U rack gear. Suitable replacement transformers are extremely hard to find and locating ones with flying leads seems impossible

I recently bought some Chinese R-core transformers but they're about 2mm out of spec and are just too tall to fit in 1U

Quite a few of the more modern units have ±15 and 5V supplies. I can't find suitable transformers to fit in 1U, so may have to use two transformers. Or I could by pass the power supply altogether and install a Meanwell triple-output power supply

Looking at schematics it's obvious that there's an analog earth and a digital earth. Any thoughts of whether a Meanwell will work successfully or not? I know the answer is to suck it & see - I have ordered a couple and am awaiting delivery

Typical power supply schematic below (Roland SDE-330)

 

[Khron]

I hope you're aware that "a Meanwell" doesn't really mean much of anything. Surely they manufacture power supplies in a much wider range of form factors than the specific one you may or may not habe in mind. I can only speak for myself with certainty, but i suspect none of the other forum members are mind-readers either

That being said, if the current ratings are sufficient... Surely those triple-output supplies don't cost that much, that it would be unreasonable to take a chance on one and see how it works out.

78xx/79xx series are rated for "only" up to 1.5A, so anything above that should be plenty.

 

[mrclunk]

What about using low profile pcb mount transformers and making a little mount pcb?
e.g
https://www.mouser.co.uk/datasheet/2/177/229-1390050.pdfhttps://www.mouser.co.uk/datasheet/2/410/FP16_3000-781716.pdfhttps://uk.rs-online.com/web/p/toroidal-transformers/1243876?gb=b

 

[pvision]

Making up a PCB is an idea I hadn't thought of

I'll report back after trying a Meanwell. I think the model I looked at is an RT-50C. They are 46mm tall so will fit in 1U

 

[mrclunk]

Those meanwells are defo worth trying.
Maybe common mode chokes / caps on the PSU output to filter HF crud if noisy?
That's what they tend to do in modern gear.

 

[JohnRoberts]

I think Wayne has compared the noise output from sundry switching power supplies over at his Pro Audio Design forum.

By all means make sure they are agency approved while CE marking can be self certified so I would stick with a well known name. Meanwell are a known maker, while I never used one.

JR

 

[MidnightArrakis]

Making up a PCB is an idea I hadn't thought of

I'll report back after trying a Meanwell. I think the model I looked at is an RT-50C. They are 46mm tall so will fit in 1U

[Making up a PCB is an idea I hadn't thought of] -- Within all of the electronic equipment that I design, I much rather prefer to use PCB-mounted transformers than a "chassis-mount" transformer with flying leads, even for tube equipment. While it "may" take up more PCB space, I have found that I can use one PCB transformer for the -- B+/HT voltage -- and another PCB-mounted one for the filaments/heaters. I have found PCB-mounted transformers that can supply 6.3VAC at over 5-Amps and still be rather small. In most cases, I may use a 6.3VAC @ 3-Amps transformer and have it small enough to easily fit within a 1U rack-chassis and still have plenty of "current headroom" left over!!!

[They are 46mm tall so will fit in 1U] -- HMMMMmmmmmm.....maybe the height of a 1U rack-chassis is different over on your side of "the pond" but, over here in the States, the nominal height of a 1U rack-chassis is 1.72 inches high (43.69mm) with a maximum internal height dimension of 1.59 inches (40.39mm)!!! YES!!!.....the 1U rack height is shown to be -- 1.75" (44.45mm) -- but, there is a nominal clearance of 30-mils (0.762mm) allowed so all of the equipment chassis will easily fit within a normal rack. Otherwise, you will need a rubber mallet to pound your new equipment into a rack so it can be mounted in place!!!

Some of my examples:

https://app.box.com/s/exihmfu3hx6s4zf9icxisobrko96ow4f
Just my 2-cents worth!!!

/

 

[scott2000]

This is used in the Apogee Rosetta...1u...

https://www.digikey.com/en/products...5915&msclkid=b952976eeee61c40211df760c4860477