Safer power supply

[pingosimon]

I've been reading through old posts and you guys scared me away from my C64 PSU (good thing I have a Sammich, too!)

I know we're supposed to be very DIY, but I'm getting burnt out on electronics, and I really don't trust the lives of my 8 SID chips to my electronics skills.

Are there detailed instructions on building/modifying a PSU, or better yet, are there any for sale?

[ytsestef]

This thread is all yours! Long thread, but very useful info in there.

I, for one, am using a Meanwell RPT-60B for the MBSID I'm building right now.

[m00dawg]

That thread is perhaps my favorite all time thread on the MidiBox forums. Pretty much everything you need to know about basically any PSU option is convered in there. It IS a long read, but man it's so educational and I still reference that thread on a semi-regular basis. I actually think that thing should probably be a sticky thread.

[technobreath]

Man, this is a nice thread. And man, there has happened a lot with availability in good switched regulators since that thread started. I have previously said I would never be converted to do switchers instead of linear, but with the speeds of modern switchers, this all seems way more attractive to me than before. But in that thread there are lots of info if you are hungry for that.

Another tip that I can give you - if we step away from the DIY (oof hehe) for a little while. Many people buy their power supplies anyway, so I gather it is OK hehe. My thought is - get someone to help you build it if you (after reading the thread) isn't able to build it yourself. You know any electronics students? or one that teaches it? Don't even need to know people - you could contact a school where they teach electronics - I bet designing and building a power supply like this would be an interesting project for at least a couple of students. Just a thought.

But then again, I really really want to encourage you to learn this yourself. A basic powersupply is basically made out of 3 parts. 1: rectifier 2: smoothing caps (which is related to rectifiers) 3: regulation/protection. Regulators made out of ICs (most common around here at least) mostly has the protection you need in most cases (temp.shutdown, over current shutdown and so on). If you study these things - and there are a lot of online material - you should be able to construct your own. Be sure ALWAYS to use fuses though. IMPORTANT :). <- might not help you protect the circuit from getting "fried", but it will probably prevent fire :D. I have had myself a PCB on my bench cooking / frying becasue I had no fuse when there occured an error - haven't concluded what went wrong there yet, but we think it's a faulty vreg. That in combination with a big battery and no fuses made PCB cooking possible.

EDIT/ADD:

I have no idea how this works in USA, but in Norway I would make a phonecall to teacher / faculty bossy guy, and present my project / my intentions of calling him...

http://www.ece.ucsd.edu/

No idea what kinda place this is - after all, I'm only a norse guy. But it looks like they are good enough equipped to help you out if they want to :).

Edited July 23, 2012 by technobreath

[ytsestef]

Agreed, making your own linear PSU is no big deal, you just need to calculate the current drain of the whole circuit and then add some more juice ;)

All of my previous DIY builds use custom linear PSUs designed and built by me, but I have no idea about switching PSUs, and I needed something small and lightweight for my synth, that's why I bought one :)

[pingosimon]

I, for one, am using a Meanwell RPT-60B for the MBSID I'm building right now.

What kind of plug is on it? I'm assuming not a C64-style DIN, so do you modify your Midibox, or the power supply?

[ilmenator]

What kind of plug is on it?

A 2 second search on the Internet returned this: Meanwell RPT-60B.

[pingosimon]

I actually got as far as this: http://www.meanwelldirect.co.uk/public/ranges/pdfs/r733/r733_3.pdf before asking, but I'll rephrase:

To those who use a pre-built power supply: Do you modify the jack of the MB6582, the plug of the power supply, or do you use some sort of adapter?

[ytsestef]

I am building my own version of MBSID, not a MB6582, but you need to put the Meanwell PSU in an enclosure, mount a C64 style socket on it (or any socket for that matter), then make a cable from "whatever-plug-you-have-used" to C64 DIN plug with correct pinout and bypass the MB6582 "optimized C64 psu" circuit by leaving out/bridging any rectifier/regulator etc (you have to check the MB6582 schematics to be sure, I don't know much about MB6582 but if it has a C64 connector I bet it has such a circuit integrated).

The Meanwell RPT60-B PSU doesn't need any sort of modification to work with MBSID projects (but the C64 PSU does, that's why you need to bypass it if it's already in the MB6582 board).

Cheers!

Edited July 26, 2012 by ytsestef

[technobreath]

Just thought I'd shoot in a comment. I can't remember it being discussed in this thread. The MeanWell powersupply is: "Fixed switch frequency at 100KHz" - which is well above audible range. But it might be a bad idea to go there if you record or if it is possible that you will ever record it with those high sample rates, 192khz, no? It is IT and Med. equipment approved, but that does not automatically mean that this is suitable for musical applications... Just a heads up if some of u didn't think of it already.

If building your own is an option - then have a look at this: http://www.murata-ps.com/data/power/oki-78sr.pdf <- switch frequency @ 500khz. I have seen similar ones @ 1 MHz too, but then it get a bit more spendy :P. This one is fairly cheap @ Mouser, but expensive in comparison to linear regulators bought from shanghai @ ebay :D.

I have not much experience in building switchers. It's a bit more rocket sciency than the most basic linear designs, but not impossible at all if you read some d.sheets, app. notes. of course it helps if u know a thing or two about electronics. <- which can be learnt also :). I have learnt most of what I know from internet studies. But also from some electronics school books I got from a friend and also some from my brother way back - really helps you grow an instinct on how to seperate the good stuff from the bad stuff online. I also had VERY much help from many people @ midibox.org.

So I know that:

...or better yet, are there any for sale?

... you don't need to go there - at least not in the long run. You probably buy one now (and we have no problems with that hehe), but I guarantee you will enjoy making your own once u get a bit more hang of the elctronics.

EDIT:

don't know much about MB6582 but if it has a C64 connector I bet it has such a circuit integrated).

It has the DIN c64 power connector indeed. And it also got regulation circuit. BUT read the wikipedia site - it's all in there - there are several powering options, and not reading this, just assembling it and put the plug in and power it up is not a smart thing to do at all.

The Meanwell RPT60-B PSU doesn't need any sort of modification to work with MBSID projects

You are partially right here. You are right, it gives you v5 and +/-12V. But SID 8580 and 6582 does NOT accept +12V without a fight. They need +9V. 6581 uses 12V. Also be aware of the powering specs of the -12v rail (depends on what you are using it for, but it might not be big enough).

So basically what you can do is to leave the vregs on the PCBs where the 9v SIDs is gonna live, then feed it with all the 12v you want ;).

It is important to think of PSU as a the whole circuit, not just the external stuff u buy or build -> there might be PSU components on the midibox pcbs also :).

(but the C64 PSU does, that's why you need to bypass it if it's already in the MB6582 board).

The C64 brick needs modifications? No, it just needs external regulator circuit to give u everything you need. I understood what you meant ytsestef, but I just wanted to clarify what you were saying.

On MB6582, you have the luxury of setting it up for all kinds of powering options. It is described very well by Wilba in the wiki pages.

Have a nice day / morning ;).

Edited July 27, 2012 by technobreath

[orange_hand]

Hi,

check this out. I use the regular C64 power plug in my MB6582.

Cheers

orange

[ytsestef]

Technobreath, when I meant "modifications" I meants not only regulation but also rectifying (9VAC to +9V) and also the trick where the two voltages are summed to give +14V in order to regulate it down to +12V for the 6581s.

It goes without saying that 8580s and 6582s need +9V, but these are already on the SID module (that's why I said this PSU works with no mods with MBSID projects, as opposed to C64 PSU).

As for the switching noise, I highly doubt that even in 192kHz recording it will be audible, since human hearing performance is well below that. But, I see your point and I agree. Only buy this PSU if you're going to record up to 96kHz, just to be sure. ;)

[technobreath]

It goes without saying that 8580s and 6582s need +9V, but these are already on the SID module (that's why I said this PSU works with no mods with MBSID projects, as opposed to C64 PSU).

I knew you knew it :) - but I just wanted to clarify it. Believe it or not, there are many people in here that do not know natively what voltages goes to what SID, so that is the only reason why I said anything - becasue it does not go without saying for many people like it is for you and me :). And you actually need to put in the right kind of vreg on the PCB in order not to kill it. Hehe, this aint a pissing contest - I just wanted to clarify all the facts for all the people who reads it. I know u know how this works, but that aint the reason you write anything here? It's because you want to help others who might not know, and then it is just a little bit dangerous to assume that they know all the things you take for granted. So please, no hard feelings at all, I am now / wasn't in the last post after you ;).

[ytsestef]

You were very right to clarify that :)

I just assume that before anyone even thinks of starting such a project, should read at least the basic stuff (manual, each module's design and build manual etc), and that should be the case, but I am wrong in doing so. Thanks for clarifying my post, you are very polite. No such thing as hard feelings or pissing contest, we are all here to learn and then help someone else :)

[ilmenator]

As for the switching noise, I highly doubt that even in 192kHz recording it will be audible, since human hearing performance is well below that. But, I see your point and I agree. Only buy this PSU if you're going to record up to 96kHz, just to be sure. ;)

Careful with that. Sampling at 192kHz gives you a Nyquist frequency of 96kHz, which is just 4kHz away from the PSU switching frequency. In other words, what you get is noise in the 4kHz range. You are VERY likely to hear anything in that frequency range that is not properly smoothed out.

But then, there is no good reason to use a 192kHz sampling frequency anyways, apart from a big ego and wallet, maybe :whistle:.

[technobreath]

But then, there is no good reason to use a 192kHz sampling frequency anyways, apart from a big ego and wallet, maybe .

Hehe, right! :P

[wicked1]

Ive made a switching supply, for tube filaments!! That's the last place you'd classically use one.. But it works very well! I used a lm22673. They have this awesome "webbench" tool that basically designs the circuit for you. http://www.ti.com/product/LM22673#toolssoftware Choose a good inductor and final capacitors, and you can get practically no ripple. The webbench tool will run simulations for you, to pick the best components for your voltage/current requirements.

I'm building a linear +/-12v and +9v and switching 5v supply right now for my 6582/filters.

[Shuriken]

Ive made a switching supply, for tube filaments!! That's the last place you'd classically use one.. But it works very well! I used a lm22673. They have this awesome "webbench" tool that basically designs the circuit for you. http://www.ti.com/product/LM22673#toolssoftware Choose a good inductor and final capacitors, and you can get practically no ripple. The webbench tool will run simulations for you, to pick the best components for your voltage/current requirements.

I'm building a linear +/-12v and +9v and switching 5v supply right now for my 6582/filters.

Nice wicked1. I have all the components for a switching 6582 psu. Bought the lm22676 and lm22675. But havent gotten around to get some pcb made yet.

[wicked1]

Not sure if I should hijack this, or start a new thread.. but my bipolar supply is a fail. I made it basically like what's on the wiki. http://www.midibox.org/dokuwiki/doku.php?id=bipolar_12v_psu&s

But, I don't have anything hooked to the negative supply right now, and it hums pretty bad. I think because the load is so unbalanced. I rewired it w/out the center tap (My transformer is a 2x12v, so I can wire it w/ or w/out a center tap) and made a unipolar positive supply, and it works perfectly.

Actually while typing this I think I thought of what to do, but maybe someone can tell me if I'm on the right track. I'll just use it as dual power supplies, using the two secondaries of the transformer individually.. no center tap. One positive supply, one negative supply, and connect the grounds together after the regulators. All it will cost me is another bridge rectifier. Does that sound correct?

Shuriken,

Someone on the DIY Audio forums made a PCB for the filament regulators. I believe the circuit would be the same for these.. I think the pinout and footprint is the same for the various regulators in the lm2267 line. (Double check, obviously).

http://www.neurochrome.com/audio/?page_id=361 There's a link to the PCB sales page on there.

[Shuriken]

Not sure if I should hijack this, or start a new thread.. but my bipolar supply is a fail. I made it basically like what's on the wiki. http://www.midibox.org/dokuwiki/doku.php?id=bipolar_12v_psu&s

But, I don't have anything hooked to the negative supply right now, and it hums pretty bad. I think because the load is so unbalanced. I rewired it w/out the center tap (My transformer is a 2x12v, so I can wire it w/ or w/out a center tap) and made a unipolar positive supply, and it works perfectly.

Actually while typing this I think I thought of what to do, but maybe someone can tell me if I'm on the right track. I'll just use it as dual power supplies, using the two secondaries of the transformer individually.. no center tap. One positive supply, one negative supply, and connect the grounds together after the regulators. All it will cost me is another bridge rectifier. Does that sound correct?

Shuriken,

Someone on the DIY Audio forums made a PCB for the filament regulators. I believe the circuit would be the same for these.. I think the pinout and footprint is the same for the various regulators in the lm2267 line. (Double check, obviously).

http://www.neurochrome.com/audio/?page_id=361 There's a link to the PCB sales page on there.

Probably best to start a new one and then post your original schematic.

[wicked1]

Well, not really worth it. My idea works, I've got positive and negative w/ no buzzing now.

But, the wiki "center tap" option isn't a good idea for running the 6582 and filters... There's practically no draw on the negative half, and everything is pulling from the positive. Center tap supplies apparently don't like that.

[ilmenator]

But, the wiki "center tap" option isn't a good idea for running the 6582 and filters... There's practically no draw on the negative half, and everything is pulling from the positive. Center tap supplies apparently don't like that.

Could you add a similar comment to the wiki page then? It might prevent others from repeating your bad experiences!

[Hawkeye]

A viable alternative might be not to use the expensive "center tapped" transformers (which are also quite difficult to obtain), but to use dual-output transformers, i have no big experience in this field, but personally would think, they may be more tolerant to different current draw from the two rails (i´ve just recently built a +15/0/-15v one for a "modular" vcf)

From the de.sci.electronics PSU FAQ:

 o--+ +-----+-|>|-+---+--- + (7805)

  | | 	| 	|   |

  S:S  +--(-|>|-+   |

  S:S  |  |  	   C1  (C1, C2: 4700uF ergibt 2V Ripple = 'Kondensatorverlust' bei 1A Belastung)

  S:S  |  +-|<|-+   |

  S:|  |    	|   |

  S:+--+----|<|-+---+

  S:       	+-- Masse

  S:+-----+-|>|-+---+

  S:| 	| 	|   |

  S:S  +--(-|>|-+   |

  S:S  |  |	    C2

  S:S  |  +-|<|-+   |

  | |  |    	|   |

 o--+ +--+----|<|-+---+--- - (7905)

Many greets,

Peter

Edited July 29, 2012 by Hawkeye

[Shuriken]

If you have a dual secundairy transformer, making a fake centertap is not a good idea. It is better, as you said, to use two bridge rectifiers.

The schematic on the wiki isn't great. First off all the LM79xx series need a bit of load (10mA) to regulate. Most schematics use a led with a 1k resistor. And it is best practice to put 2 diodes in for polarity protection.

For example:

The article on the wiki is probably in need of an update. nILS made a modular PSU where he did use diodes.

Edited July 29, 2012 by Shuriken

[wicked1]

Could you add a similar comment to the wiki page then? It might prevent others from repeating your bad experiences!

Someone has me thinking I could have possibly had a ground loop causing the problem. I'm going to test that theory. If it's definitely the unbalanced load causing the problem, I will update the wiki.

A viable alternative might be not to use the expensive "center tapped" transformers (which are also quite difficult to obtain), but to use dual-output transformers,

Mine is dual secondaries, so that is what I did. Only, I didn't connect the grounds together until after the regulators, where your example has them connected after the rectifiers. (I'm not an EE, and don't know what difference that makes.. works, though)