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I figured this would make a helpful thread, as I just went through this process and found a distinct lack of information. I'm really grateful to everyone who pitched in advice, in particular consumed and flts who pretty much gave me the info that made everything click.
So for anyone who is curious, or looking over the DIY forum at a later date or whatver - here's some info about wiring up your own power supply, instead of being a slave to the (fairly expensive and lower output rating) modular manufacturer's options.
(no offense intended, the Blacet PS500 is a super awesome power supply and a great deal for pricing, and i'll continue to use them in my frac rig)
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So you have probably heard about people getting power supplies for their modular synths from the electrical supply industry, instead of the modular synth providers. There's some benefits to this approach - and some drawbacks.
Benefits:
- Much higher possible output ratings. A Blacet PS500 gives you half an amp. You can buy power supplies that will provide you with 1,2,3,4,6,8,12 amp, etc etc. Of course the larger ones are a lot more expensive than the smaller ones, but even the smallest typically provide more power than a PS500.
- Better "dollar per amp" ratio. For what you pay for a Blacet supply, you can get about twice the power in a commercial linear power supply. For small increments more in cost, you can get more and more power from the supply.
- Less need for multiple power supplies in your synth. Buy a big enough supply and let your synth grow grow grow.
Drawbacks:
- Big-ass and heavy.
- Hard to know what to order. Webpages and published specs read for electricians. Nothing has names, just wacky huge model numbers related to some spec that I don't really understand.....
- No AC input wiring. These power supplies are designed and sold to be integrated into existing equipment, anywhere in the world. As a result they do not have any AC input (the wire you plug into the wall) at all. They do have a transformer that you can wire ANY type of input voltage (from anywhere in the world it happened to be sold), but it must be done differently depending on your application, and none of the wiring is provided. Instructions are typically technical and terse, difficult for the novice to understand.
- Linear DC power supplies require a fuse inline with their AC input. The size depends on the application. None of this is provided with the power supply.
- Need calibration. Often the power supplies also need to be calibrated for the target application, many have multiple available output ratings so you have to set it up for the correct one.
- Not a lot of information in the modular synth world about how to set these things up. The price and power seem attractive, but they are far from 'ready to go'. I own ten Blacet PS500s. Ten! So attractive as they are plug 'n play... anyway. Hopefully this thread helps solve that problem.
- How to hook it up to your modular's power bus? How?
- Quality? I'm not sure about this one. I could be talking out of my ass for sure, but I don't know enough about things to say if these commercial supplies provide the same quality juice as that old benchmark, the PS500. I do know that Grant R. of Wiard told me that there's no point in looking for another supply while the PS500 is available - it's the best there is. I dunno.
So anyway, I personally have forged on and on with the Blacet supplies, however with my recent foray into the world of Eurorack, fate conspired for me to end up with one of these PSUs, and not a single clue what to do. I answered all my questions, and got it all set up and now have a 3.4amp eurorack power supply. I stalled and stalled, as I refuse to pay in the ballpark of $450/rack for Doepfer rack&power, and knew something would eventually come up. Thanks Felix for the awesome power supply!
Anyway, I got one of these puppies up and running, and I'm a blathering idiot. If I did it, you probably can as well.
Here's everything I learned, distilled down into a process that I hope will be helpful.
Before continuing on, you *MUST* read, understand and accept the disclaimer. Use of the information in any form constitutes acceptance of this.
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PLEASE BEAR IN MIND I AM NOT AN ELECTRICIAN NOR EVEN VERY EXPERIENCED AT ALL. ALL I KNOW ABOUT THIS STUFF 'I LEARNED FROM SOME GUY ON TEH INTERNET AND THEN WAS DUMB ENOUGH TO TRY MYSELF'. If you use this information, you must accept the disclaimer that the information is likely erroneous and dangerous. I am not liable for any injury or damage resulting from any use of this information, or even from simple exposure to it.
Projects like this deal with AC mains voltage, large transformers and large capacitors - capacitors that can hold lethal voltages long after the power has been cut off. THEY ARE WAITING FOR A CHANCE TO ZAP YOU. IF YOU DON'T ALREADY KNOW THIS, DON'T EVEN READ ANY FURTHER.
THIS PROJECT CAN EXPOSE YOU TO POTENTIALLY LETHAL VOLTAGES. YOU COULD DIE. If you are a dumbass about respecting the potential danger here, you probably WILL die.
If you are not comfortable and actually truly know what you are doing in order to keep yourself safe, DO NOT ATTEMPT THIS PROJECT.
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Ok, so now let me tell you what to do so you can go off and fry yourself.
Please read EVERYTHING once. Then wait, then read it again. If you are going to do this project, read it again the next day, and the next day, and then the day before you do it, and then the day you do it, right before you do it.
You could end up building something that worked properly, but had exposed terminals inside that may fry someone some day far into the future. You could sell it, still working fine, years from now, and it could kill someone. If you build it, build it so it will be safe, because you are responsible for any damage it causes. It could start a fire. It probably will. You probably shouldn't build it.
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Here's what you'll need (I'll discuss 'em all below)
- Buncha tools. I'm not going to list them! You know, pliers, wire strippers, wire cutters, screwdrivers, all that shit.
- Buncha hardware. You know. A handful of bolts, nuts, washers, etc. Not gonna list 'em. Just some random ones for mounting the odd thing you may have to.
- I will list the fact that you need a soldering iron, and some NO CLEAN solder.
- Insulating Heatshrink tubing. Seriously important for safety. DO NOT skip this.
- Digital Multi Meter.
- Stranded wire. 600V
- AC Power inlet
- Fuse holder
- Fuse (Slo-Blow type, rating depends on country)
- Terminal ring
- Zip-Ties, but I *know* you already got 'em
- Most importantly, a DC Linear Power Supply.
Now this is a 'bare minimum' list of materials. It doesn't let you make an enclosure, have an on/off switch, no mounted place to plug in the wire, nothing. This is pure basics. if you do not have any one thing in this list (except for possibly the zip-ties, but I *know* you already got 'em) I do not think you'll be able to do this project. Don't be in a rush, wait 'till you have all your stuff.
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Ok, about the things you'll need, the only ones that really need much discussion are the PSU itself, the Power Inlet and the fuse setup. The other things are pretty self explanatory.
About the power supply, what you want is a "DC Linear Power Supply". It seems the medical industry is a common purchaser of these. They are made by companies like PowerOne and Condor. You need to make sure that it supports output of +/-12v (Eurorack) or +/-15v (Fracrack). Most are capable of a variety of output voltages, and it can be adjusted when installed. Make sure 12v or 15v is within the range. The 'strength' of the thing will be it's output rating, wich would be something like 3.4amps, 6amps, etc etc. An amp is 1000ma, so a 3.4amp supply will give you 3400ma for your modules. The higher the output rating, the more expensive the supply will be.
Here's my supply:
As you can see, it's model is HCC-15-3-A+ G
If you look below that, you can see that the input and output ratings are listed. It accepts most input voltages around the world, but it must be configured properly in order to use the one at the installation. You can see there is two output ratings - 15v at 3amps OR 12v at 3.4amps.
At the bottom you see an exclamation mark in a triangle. This is telling you to watch out about something! WTF! It's warning you about "Ext and a rectangle with a line through it". Yeah. Actually, it's telling you an external fuse is REQUIRED on the power input to this. I think it should use words to tell you this, but hey, picky picky.
To the right of the warning, you see a little chart. This chart is reproduced in the very very scant piece of 'instructions' that come on a piece of paper with the power supply. This chart tells you how to configure the power supply to deal with whatever input voltage you are using. Important stuff! We will need to do this later, so let's look at it. I have 120v AC here, so I need to set it up for that. Fortunately, it's in the chart. The chart says to 'jumper' 1-3, and 2-4, to 'apply' 1 & 4, and to use a 2.0amp fuse. We will need all this info later.
Here's what the back of the unit looks like. When you get a supply like this, what you see in this photo, and the one above, is all you get. When I said there was no AC inlet wiring, I meant it.
If you look at the large transfomer, there are five numbered terminals on it. Note that the numbers are NOT in order. These are the terminals we use to jumper and to apply incoming AC voltage, according to the chart above. So, what we would do is solder a piece of wire between the 1 and 3 terminal, and solder another piece between the 2 and 4 terminal. We would then apply our incoming AC voltage to the 1 and 4 terminals, and we would need to have a 2.0amp fuse inline with this input. If you have all the stuff, if you want to right now you can solder the two jumper wires. Don't do anything else yet though.
If you can, solder the wires from underneath, so you can sort of fold the wire down and towards the transfomer - this will make it easier to get heatshrink over the whole part later on.
If you look at the left-hand part of the inside of the unit (above) you see a circuit board with some trimmers, and seven posts at the bottom. The posts are where the voltage out of the supply comes, and where you will hook up the power bus of your modular synth later on.
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Now moving on to the AC Inlet - there's two types you can buy. The best bet is the type that has the fuse attached as part of the inlet piece (the fuse is installed in a little drawer under the inlet plug). If you do this, you do not have to worry about getting and wiring the fuse holder, and can omit it from your basic bill of materials. Here's what one of these looks like:
I could not find that type anywhere in town, and I was impatient, so I bought a basic AC inlet, which looks like that one but not as tall - it doesn't have the drawer underneath. I did this because I was able to find an inline fuse holder that would work. The part looks like this, but the circular wire is of course cut so the thing is a line:
And I bought a 2.0amp (specified by the chart on my powersupply) slow-blow fuse to fit in it. The fuse and holder were both loose and rattling around, so I mashed the spring down and coated the whole thing in hot glue-gun glue. I was frustrated. When cool it felt solid and passed continuity testing with my DMM even with lots of moving around. So no problem.
Ok, so you're better off to get the AC inlet with the drawer. If you do, put your correct fuse in there. If you get the inline holder, here's what you do:
Cut a piece of heatshrink tubing and slide it down one end of the inline fuse holder, then solder the end of the fuse holder's wire to the positive (left when looking into the inlet's plug) lug of the AC inlet. Now take an AC cable (the thing you plug into the wall), make sure it is NOT plugged into the wall, and plug the other end into the AC Inlet you are making. Take your DMM, and check continuity between the positive plate of the AC wire's plug (the part you shove into the wall socket) and the far end (after the fuse) of your inline fuse holder. If continuity is good, you're set - pull that heatshrink down over all the metal of the lug and shrink it so it's tight and stable.
Now, cut another piece of wire, about as long as your inline fuse holder. Slide anoter bit of heatshrink down it. Now solder it to the negative lug of the AC inlet. with the dummy power cord you have, check the continuity between the negative plate and the far end of this new wire. If continuity is good, cover the lug with heatshrink as well.
If you have the AC inlet with the fuse drawer built-in, then just solder two wires, one to the positive and one to the negative lugs of the inlet, test and heatshrink.
Now you need to make your ground wire. Cut another new wire, put two seperate pieces of heatshrink on it. Attach a terminal ring to one end, check continuity, heatshrink. Attach the other end to the ground lug of your AC inlet. Check continuity, heatshrink.
You now have an AC inlet and a fuse, one way or another. It's time to hook them up to your power supply.
Looking back at that chart - we have to apply to terminals 1 and 4 of the power supply's transformer.
At this point, if you haven't jumpered your transformer for the correct input voltage, do it. You may need to check with the documentation for your supply if it is not marked on the supply itself. Now put new heatshrink tubes on the two wires coming from your AC inlet, and then solder these wires to the two 'apply' lugs from your chart, in this case 1 and 4. It doesn't matter which side of the AC inlet goes to which terminal - you can reverse them, no problem.
After they are soldered, check continuity on everything again, the slide the heatshrink down on the transfomers terminals, and shrink it.
Make sure to cut little pieces of heatshrink and melt them around the unused terminals on the transfomer - these terminals can present voltage when the power supply is in use! Danger! Cover them.
You've now basically completed the section on wiring up the AC input. You just need to do two small but important things:
- Secure the inlet somewhere. Here's where I used a zip-tie. Handy! I bet you can come up with something better.
- Hookup the ground. After securing the inlet with the zip-tie, you need to take that terminal ring that comes from the ground lug of the inlet, and screw it into the metal chassis of your rack frame. Test continuity. No need for heatshrink.
(NOTE concerning the grounding connnection - this is another good tip posted later in this thread by fonik - it is recommended that you connect the ground to the PSU's own chassis, as close to the transformer as you can. There should be mounting holes on the chassis near the transformer for this purpose. This gives a more direct path to ground in case the PSU goes crazy and starts sending voltage into its chassis, and is the recommended way to install the ground. I did not do this when I first wired up my PSU and took the pictures in this post, however I will rewire my ground using this method the next time I have my rack out)
You have now configured your power supply for the proper input voltage, and you have hooked up fused AC power.
You can actually plug the power supply in now (but DON'T DO IT YET! Read more info below on how to do it safely...), and the next step is to use your DMM to measure the output voltage so that it can be configured.
So, there's really only two steps left:
- test the output, and calibrate if necessary
- hookup the modular synth's power bus.
Now, this is probably a good time for this pic - you can see the inlet, fuse holder, grounding terminal ring, zip-tie (yay!) etc.
This is actually the 'almost completed' pic, as you can see the power leads to the Doepfer busboard are also connected. The only thing I still have to do in this pic is to cover the unused output posts in heatshrink.
OK, back to the project - so we are currently at the point where the AC inlet and fuse have been all wired up, and we've made sure the PSU's input transfomer was jumpered for the correct local voltage.
That means there's two things left to do - check the output of the PSU (and calibrate if necessary), and then hook up the modular synth's wiring harness to it.
At this point, we have to do what is potentially the most dangerous and frightening thing about this whole project - we have to plug in this beast that we just made. Be afraid.
Before you even come close to trying, take this chance to inspect your work - are the connections at the back of the AC inlet correct? Perhaps retest the continuity with an unplugged AC power cord and a DMM - or maybe not. If you can easily test the continuity at this point, you probably didn't do a very good job insulating your terminals with heatshrink. Inspect your work carefully with the understanding that it could kill someone through direct shock, indirect shock, and/or starting a fire. You DON'T want that to be your fault dude. Think about it.
Ok, so we are gonna forge ahead? You gotta plug that shit in homeboy. What's the safest way you can do it? Start by putting the PSU on a stable, clear surface where it will not cause other things to ignite if it catches fire. Make sure no-one can bump it, knock it off the table, slip and fall onto it, etc. Treat it like it is cancer - keep everything the fuck away from it.
GET A FIRE EXTINGUISHER AND HAVE IT READY
Now, you have the PSU somewhere safe. Plug an AC power cord into it. Plug that cord into a decent powerbar, one with a fuse in it if at all possible.
If you can, plug that into an extension cord, so you can go somewhat far away from the PSU when you plug in the cord.
Don't stand directly over the damn PSU when you are plugging it in.
So, when you're good - plug it in. Probably nothing at all will seem to happen - almost a letdown. No sparks, no flame, no hum, no explosions and the dying and the screaming, nope. Sweet silence.
If something other than silence happens, unplug the power cord, and either put out the fire or otherwise just run for your blessed life.....
so, it all seems good - you should probably unplug it so you can go back over and plug it in using a sensible power cable instead of the long safety cord you just had. BE CAREFUL TOUCHING THE POWER SUPPLY - VOLTAGE REMAINS ON THE OUTPUT TERMINLS FOR A FEW MINUTES AFTER POWER HAS BEEN REMOVED - FURTHER INFORMATION ABOUT THIS BELOW
It's now time to test it and see if it is actually providing output, and test what the voltage of that output is. Let's take a look inside the power supply again -
Note at the bottom edge of the curcuitboard are 7 posts. Your power supply may have less (possibly more? I don't know. Either seven or less most likely...anyway...)
The posts are labelled:
-OUT
-S
-S RTN
COM
+SRTN
+S
+OUT
I really don't know about the S and S return posts. I was not using them, so I took those four posts, and covered each one with a snip of heatshrink so that they would not shock anyone. MAKE SURE YOU DO THIS
(EDIT: I now *do* know what's up with these 'S' posts - thanks to fonik. They are to wire up 'auto sensing' of the load, allowing the PSU to regulate its output providing constant output. While I did not know about this when I was setting up my PSU, these terminals were preconfigured when this PSU was assembled at the factory to USE the auto-sensing feature. For more information about auto-sensing please read the last two paragraphs in this post. If you want to hook up the auto-sensing (and I cannot say for sure if you do or don't - but it makes sense to do so, mine was preconfigured this way anyway), connect your '-OUT' terminal to the '-S' terminal. Next connext '-SRTN' to 'COM'. Then connect '+SRTN' to 'COM'. Finally connect '+OUT' to '+S')
The remaining posts are:
-OUT
x
x
COM
x
x
+OUT
Pretty self explanatory. We need to figure out what voltage is coming out of there. Plug in your PSU, and then take your DMM and set it to measure DC Volts in the 20v range.
FIRST, hold the the BLACK lead of the DMM on the COM post, and then...
SECOND place the RED lead of the DMM on the -OUT post. Hold them both there, and read the value on your DMM. If you are setting up a frac power supply, you want it to read -15.0v If you are setting up a Euro power supply, you want it to read -12.0v.
Take mental note of the value you see.
WHEN YOU REMOVE THE LEADS FROM THE POSTS, REMOVE THE RED LEAD FROM -OUT FIRST, AND THEN THE BLACK LEAD FROM COM SECOND.
Now repeat, and this time checking the +OUT post with the red DMM lead. Take mental note of the value you see. Move the DMM away from the PSU.
Now, are the values correct? If not you need to adjust them. I took a reading of +14.6 and -14.4 on my PSU when I set it up.
You need to figure out how to set them. On some, there are jumpers on the PCB that can be installed or removed. In which case there will be information somewhere telling you this. In the case of my supply, it was done by adjusting two trimpots, one for the positive side and one for the negative side. This information was not printed anywhere - I made a guess and tried adjusting the pot while measuring the voltage, and saw that it worked. I got both of them set to exactly 12.0v, nice and stable.
Once that's all done, you're done! All you need to do is hook up your modular synth's power harness to these outputs from the PSU, and of course mount the PSU safely in your case.
MAKE SURE YOU UNPLUG THE PSU BEFORE SOLDERING ANYTHING TO IT!!!!!!!!!!!!!!!!! damn, i'm glad i remembered to mention that.
IMPORTANT NOTE - also, after you unplug it, those big capacitors in the PSU take a while to discharge completely - I noticed this by continuing to measure output with my DMM after unplugging the power - it took a little over two minutes for the voltage at the output posts to fall to zero. Always check. When working with electricity, ALWAYS CHECK, AND CHECK AGAIN, AND AGAIN. If you aren't sure, test something with your DMM before you touch it with your damn hands. I'm trying to keep you from getting hurt!!
Ok, for connections, I was connecting a Doepfer busboard to the supply, and will simply chain additional busboards off of the first one. I took one of the Doepfer busboard cables, connected the red wire (+12v) to the +OUT post on my power supply, connected the black wire (COM/Ground) to the COM post on my PSU, and finally connected the blue wire (-12v) to the -OUT post.
As always, once your soldering is done do a continuity check with your DMM, and then heatshrink and cover any exposed conductive materials.
That's it!! You've done it!! YOU HAVE THE POWER. LIVE THE DREAM.
Oh, if you are connecting to frac-rack, same drill, except you'll want to run two wires from the COM post, to go to the two seperate COM returns on the frac power harness.
Have fun with all the power and please, please, dammit, please don't get your sorry ass hurt.
One final note: Some time after I did this, I learned something new about these supplies, that was not mentioned in the scant 'documentation' that came with my PSU, nor mentioned anywhere else that I had ever seen. It turns out that there is a function on many of these PSU's called 'remote sensing', letting the PSU feel out the amount of current being drawn, and regulating its output to provide a constant voltage. On some PSUs this needs to be wired up if you want to use it - on mine, it was configured at the factory to USE the remote sensing function, so it did not matter that I wasn't aware of it. However if your PSU requires it to be wired up, that's one other thing to think about.
There is some debate concerning if this is important or not to do with modular synths - some major manufacturers do not configure remote sensing on their modular synth PSUs. Sorry I don't have more information here. The issue of remote sensing was brought to my attention by fonik, in his post on page 3 of this thread. It's right near the bottom of the page, third post from the end of the page. Please have a look at this post and the followup comments, as it is relavant information to hooking up the remote sensing terminals if you need to.
I have a pretty good ear - and I adore the bop music of the 60's and know a good deal of it, a lot of the standards anyway. All Blues is the only thing I can play really well (I'm a huge Ron Carter fan, he is my favorite bassist, Charlie Haden second....), but I can hack around Walkin' and My Funny Valentine and a handful of the tunes Miles' band was doing in the day.
