SCULLY 280 POWER SUPPLY QUESTION

Kinda new to GDIY sorry if this is in the wrong location.

I have no EE degree but am very handy with an iron.

My question is, can I simply buy a ten dollar 24v adapter for these things and wire them Pin. 4=  neg. 24 volts input (from negative psu terminal) Pin. 3= "psu amp ground" (from positive psu terminal)? I see some old printer power supplys going for ten bucks on ebay. If I dont care about phantom, this should just work right? I'd rather build the power supply but I would need detailed instructions. (if that exists, I can't find it.) THANKS VERY MUCH GUYS!

JML in NYC said:

My question is, can I simply buy a ten dollar 24v adapter for these things and wire them Pin. 4=  neg. 24 volts input (from negative psu terminal) Pin. 3= "psu amp ground" (from positive psu terminal)?

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yes. 
kinda micky-mouse if you don't mind me saying.
there is a primitive  regulator in the 280 electronics assembly.
a 280 deserves good power,  24 VDC linear power supplies are inexpensive.

Ive opened up some of those power supplies from old printers ,they contain a transformer ,a bridge rectifier and a reservoir cap ,its isnt however regulated ,which is most likely what you need for your application . There are many kit regulators available off ebay cheap ,they usually only require a transformer and an enclosure ,there easy to solder up yourself too .A switchmode powersupply is another possible option ,these can be found cheap in a variety of different voltages ,they can sometimes be noisey though .
Remember also to work out what current is required , try ebay search for 'linear 24volt power supply' bound to be lots of cheap options there .If you find something you like the look of ,bounce the link back in here ,and we can give you an opinion as to its suitabillity .

Yes but a high quality AC/DC switching mode power supply (SMPS) is just cheap. If you want +-24 lookup Mean Well IRM-20-24 or LPV-20-24 on Mouser or Digikey. Adjust the model for your power requirements. If they are transformer isolated they can be "stacked" to make + and - voltages (if you look at the block diagram in the datasheets you can see a transformer and opto-isolator which is a very strong indication that they are in fact isolated and can be stacked). If you add chokes and small filter caps it will be very quiet and superior to a linear supply in many ways. Even modern consoles use SMPS now. There is basically zero reason not to use SMPS.

Id say the Scully is single 24volt rail and all discrete circuitry .

Tubetec said:

Id say the Scully is single 24volt rail and all discrete circuitry .

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Right. Sorry. I didn't read the post carefully. So making just -24V with an AC/DC SMPS is no problem.

Would any of these work? Sorry for the noob level of electronics understanding here, I'm here because I'm trying to learn. I've built many DIY mic pres/comps/ eq's etc but my degree is in audio engineering (as where I'm a mix/tracking engineer not a tech), so I am usually reliant on instructions or simple schematics when taking on a build. I really appreciate your help here, very much so. I know the unit requires 24 but not sure what other perameters I should be looking for in a product description. This is the one I'm looking at:
https://www.ebay.com/itm/Altronix-AL624-Linear-Power-Supply-Charger-6Vdc-12VDC-1-2-amp-24VDC-75-amp/323099951047?hash=item4b3a41ffc7:g:ws8AAOSwBfNakuwZ

other options:

https://www.trcelectronics.com/View/Mean-Well/IRM-20-24.shtml

or

https://www.ebay.com/itm/AC-DC-12V-24V-LM317-LM337-Linear-Voltage-Regulator-Adjustable-Power-Supply-Kits/172179423450?hash=item2816b180da:g:tGIAAOSwU0RXHYDt

or

https://www.ebay.com/itm/Supper-Ultra-Low-Noise-linear-power-supply-LPS-PSU-KIT-5V-9V-12V-15V-18V-24V/141969655633?hash=item210e0d0751:g:ZxYAAOSwJQdW-0mH

No sure what that first one is. The Mean Well SMPS would work. The other two would probably work but they would still need an appropriate transformer.

If you're trying to do simple and cheap, you might look into an SMPS that has the wall plug integrated so that all you have to do is add a 5 PIN XLR connector to the end and to the Skully. And preferably add a choke and cap if you can finagle it onto the XLR inside. An old laptop supply might even work fine if the voltage is right.

If you're making something a little more professional, I would still use an SMPS (like the MW you linked to) but put it into an external enclosure with a proper earthed AC entry socket -> power switch -> SMPS -> choke -> cap and then a power cable to maybe a 5 pin XLR.

If you want perfection, maybe use two separate grounds (one for anything that needs to be super quiet like an input amp and then another for everything else) and add a small regulator board or maybe just a capacitance multiplier just inside the XLR5 socket.

Yeah the first one you showed looks more like a battery charger type circuit ,noise isnt an issue for battery charging ,but it most likely wont make a great psu for audio .

The second unit you show certainly will do the trick ,and its very reasonable ,you'll only need the negative rail but having a plus 24 volts available might come in handy too . Heres another version of it ,slightly more expencive ,but with what looks like better components.
https://www.ebay.ie/itm/LM337-LM317-DIY-Adjustable-Filtering-Power-Supply-AC-DC-Voltage-Regulator-Kits/332227347705?ssPageName=STRK%3AMEBIDX%3AIT&_trksid=p2057872.m2749.l2649

The third option looks quite nice too ,but its very much more expensive , its dual rail as well .

Of course as Square mentioned you will need a suitable transformer which is an extra cost ,or you might be able to reuse something from a scrapped appliance . Less work involved using an smps alright , but extra precautions will be needed to ensure you not feeding the old Scully RF garbage.
Is it just a single module you need to power or many of them?

Oh man you guys are the best, thanks a ton ~
So I have 4 of these units but I need to build 4 separate supplies cause they'll go in 4 separate rooms.

Tubetec, that link you provided looks perfect. So to clarify, after I build this simple PSU kit, all I need is a physical housing box, a physical plug wired to the  (any old vacuum cord with a 3 prong on it will work? Where can I pick up a proper Cable for this?). Lastly, what do you mean by I'll need a negative rail? I am unclear on that...

Thanks again for all your help on this, I don't know if this project would ever get done if not for you guys, this info is incredibly valuable to me, thank you very much.

I forgot to ask, Can you shoot me a link to an SMPS that would work so I can see what you're talking about?
Something as simple as this? https://www.ebay.com/itm/NEW-Ktec-Switch-Mode-POWER-SUPPLY-MODEL-KSAS0652400270M2-24V-2-7A/152426950162?hash=item237d5aae12:g:-FsAAOSwnHZYmNUQ
And then what, just litterally cut the head off the end and solder the wires internally to pin 4 and 1 of the Scully pinout? Thanks in advance

Not all SMPS are the same. Some are better than others. Buying something on Ebay just to save a little on shipping is possibly a mistake. For a little more you can get a new MeanWell supply which are known to be good. For example, look up GST18A24 on Mouser.

IMHO you should still try to add an LC filter. If you order from mouser get 1A common mode chokes. This will block high frequency garbage from getting too far into the enclosure.

I had a closer look at the schematics ,what you have here is a record /playback  amplifier from a tape recorder ,it certainly has very nice quality Mic, Line input and output transformers and associated circuitry, but my guess is some other modifications may be needed to make it work correctly as a stand alone preamp , I have seen some posts by others who have made seperate power supply for these ,but its hard to know exactly if they work right or not . Really I think you need a techy with some experience with modding these to have a look at one  , Maybe there is someone here who's located close to where you are who might be willing to take a look .

Heres a link to the full manual relating to the 280,

http://www.technicalaudio.com/pdf/Scully/Scully_280_manual.pdf.

It looks like there is indeed +and- 24 volts rails in the psu ,but its also possible only +24volts in needed for the audio side of things , If you had a friend with a test bench maybe they could try powering up one of the modules and see if it passes signal ,this should be do-able  at no major cost in terms of time ,but again before these 40plus year old  modules will work right component replacement is very likely to be nesessary .

Heres another very cheap option for a single rail +24volt linear supply ,you will of course need a transformer(120volts primary to 24 volts ac secondary ) and an enclosure also.

https://www.ebay.com/itm/AC-DC-Power-Supply-Module-Rectifier-filter-Volt-Linear-Regulator-3-3V-5V-12V-24V/122712102127?hash=item1c923614ef:g:GrwAAOSwrNlZu5wP

No shadow of a doubt ,its an easier job just to go with the SMPS ,but very little to be gained in terms of knowledge or learning ,very best of luck with your project ,if you have more questions don't hesitate to ask .

Tubetec said:

Heres a link to the full manual relating to the 280,

http://www.technicalaudio.com/pdf/Scully/Scully_280_manual.pdf.

It looks like there is indeed +and- 24 volts rails in the psu

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Nope, just -24v for the record electronics.  A simple solution is a Power One HB24 linear supply.

I'm in Brooklyn and have some experience with these if you want to bring one by.  Send me a PM.

Thanks everyone, this is so valuable to me.
Mjrippe, this is great.  Can I simply house and wire this PSU up to the internal power strip pins (1 is + and 4 is - I believe)? If it's that easy I think that's my solution for sure. I'd come by but I'm stretching my budget already by buying 4 of these at once and the 4 PSU's Although I'm sure you're worth every penny! Thanks a ton

JML in NYC said:

Thanks everyone, this is so valuable to me.
Mjrippe, this is great.  Can I simply house and wire this PSU up to the internal power strip pins (1 is + and 4 is - I believe)? If it's that easy I think that's my solution for sure. I'd come by but I'm stretching my budget already by buying 4 of these at once and the 4 PSU's Although I'm sure you're worth every penny! Thanks a ton

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Yes, that is correct.  You will want to connect the + rail to ground at the power supply end.

The Hb24 looks perfect for the job ,  300,000 hours Mtbf ,that seems like a very very long life .I wonder how long smps's are rated for .

I found this kind on ebay ,much bigger power, enough to do a rack of 24volt gear

ACOPIAN-A24H1200

looks like good value for money,

awesome. This has EVERYTHING I need right? All enclosed ready to go? Thanks

Buy a used power one hd24 moduke. They are cheap, reliable, and output good power. Tons of them on ebay.

Hi, I've been asked to build a PSU for running two Scully 280 preamps (only the -24V for the audio amplification with and additional 48V for phantom power).
I don't have those units at the moment, so I can't test how much current each of those units draws.
Maybe someone knows the current draw for each preamp?
Does a 24vdc @ 600mA rail will be enough or do I need something larger?