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rane rs-1 power supply puzzles me
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creekree



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PostPosted: Wed Apr 16, 2008 4:57 am    Post subject: rane rs-1 power supply puzzles me Reply with quote  Mark this post and the followings unread

hi all,

my rane rs-1 powersupply (the one with the red telephone style plug) died, and a new one is VERY expensive here - around 100 euros!!
obviously i am not willing to pay that amount of money.
i found a pdf with details of the power supply at rane's website, it says that it delivers 2x 9VAC - i should be able to use two 9VAC wallwarts then, right?
please see the attached picture - i have NO idea what they mean by "center tap".
could someone please explain?
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françois



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PostPosted: Wed Apr 16, 2008 6:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello,

I do not know this one, but the most reasonable and likely guess is that you have a +/-9V supply, and what they call "center tap" is what everyone else would call "ground".

Hope I am right...

-- françois
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Uncle Krunkus
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PostPosted: Wed Apr 16, 2008 7:32 am    Post subject: Reply with quote  Mark this post and the followings unread

Yes, it's actually an 18V AC with centre tap. It means that the Centre tap is your 0V reference, and as one side swings to +9 the other side is swinging to -9 then they both swing back the other way.
In catalogues, or spec sheets, it will be called something like a 9-0-9 output or similar. If you can find two linear wall warts, with 9V AC output, which don't have a common connection back to the mains earth, you can connect one wire from each together to be the centre tap, and the other two will have 9V AC each.
I'd prefer a 9-0-9 linear transformer, as sometimes there can be issues with keeping each side in phase etc. But that would be more expensive as you then need to insulate and fuse the whole thing.

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fonik



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PostPosted: Wed Apr 16, 2008 7:49 am    Post subject: Reply with quote  Mark this post and the followings unread

Uncle Krunkus wrote:
If you can find two linear wall warts, with 9V AC output, which don't have a common connection back to the mains earth, you can connect one wire from each together to be the centre tap, and the other two will have 9V AC each.

what about the phase? i'd thought i would have to connect the "hot" from one wallwart to the "0" from the other? or isn't there such a thing?
(i'd thought the third connection of a power chord is kind of emergency exit, where power can leave the equipment, if something goes really wrong. one of the two left connectors is the hot, carrying the power, the last one is the "0").
just guessing.

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Uncle Krunkus
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PostPosted: Wed Apr 16, 2008 9:55 am    Post subject: Reply with quote  Mark this post and the followings unread

If they are both AC adapters then they should just have floating AC across the wires. Neither should be earthed, but one could be I s'pose, this would not be good. The problem is that two identical AC wall warts could be connected antiphase. Now normally this shouldn't be a problem, because each 9V AC input will have it's own rectifier, and then the +ve from one rectifier will connect to the -ve of the other and become the 0V line. But if your PSU circuit is the type which puts the outside two connections (ie 18V AC) across one rectifier and uses a halfwave rectification for each side, then the 0V will be commoned to the mid point between the two AC inputs and then the phase of the AC ins will have a lot bigger effect on the resultant DC. Most of this will be okay by the time you get past the caps and regulators, but it does make a difference.
Bottom line,
if you're building your own PSU, follow a circuit which is proven to be right for the application, and make sure you're using the right type of transformer etc. Things can go wrong. And if they do you might not get a second chance.

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fonik



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PostPosted: Wed Apr 16, 2008 11:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

thanks, krunkus. had to read it twice, but i think i got it. AC still confuses me more that DC allready does. Wink
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Blue Hell
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PostPosted: Thu Apr 17, 2008 3:21 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
AC still confuses me more that DC allready does. Wink


No wonder, just when you think you got it it's all gone & when you look again it flows in another direction Laughing

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Uncle Krunkus
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PostPosted: Thu Apr 17, 2008 4:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

fonik wrote:
thanks, krunkus. had to read it twice, but i think i got it. AC still confuses me more that DC allready does. Wink


I'm definitely no expert! The stuff I know, I've worked out from studying PSU circuits and an old book I have on PSUs. The good thing about PSUs is they usually have a little light which lights up when you've done something wrong. You've got to be quick to see it though. (A fuse Laughing ) I've lit a few of those up before. Rolling Eyes

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creekree



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PostPosted: Fri Apr 18, 2008 4:09 am    Post subject: Reply with quote  Mark this post and the followings unread

ok, so i should buy a 9-0-9 transformer then.
since i am in germany i looked for one at reichelt.de - they have transformers with 230V / 2x 9VAC and with 2x 115V / 2x 9VAC

i assume that the 2x 115V ones can be hooked up to 230V as well - but which one is preferrable?
(fonik, maybe you can help me out: offene bauform vs ringkerntrafo... keine ahnung wie man das übersetzt)


could someone post an example link/schematic for such an psu?
i found lots of schematics for DC supplies, but i need an AC one...
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Uncle Krunkus
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PostPosted: Fri Apr 18, 2008 3:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Go for the 230V / 2x 9VAC. (Gemany has 230AC mains doesnt it?)
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Blue Hell
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PostPosted: Fri Apr 18, 2008 4:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

creekree wrote:
offene bauform vs ringkerntrafo


laminated core vs toroidal transformer (see here)

As for a schematic, have a look at http://sound.westhost.com/project44.htm and leave out BR1, C1, C2 and everything to the right of that ... so you just keep sw1, f1 and tr1 - assuming the 230 -> 2 x 9v trafo ...

There is one little detail, you'll have to connect the two 9 V windings yourself and you'll have to do that the right way ... this is hard to tell for me without any further information.

As for building the thing there are certain rules that for safety reasons are best observed when dealing with mains power. I tried to google a good page for it, nothing showed up ... be sure to isolate everything very well on the mains side and construct it in such a way that it can't easily fall apart and that when it falls apart no harm can be done. When you use a metal enclosure have it grounded, better use a plastic enclosure.

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tupinamba



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PostPosted: Tue Dec 30, 2014 4:05 am    Post subject: RS-1 clone : annoying hum... Reply with quote  Mark this post and the followings unread

Hi everyone, and merry christmas!

I've built a replacement PSU for a friend who has lost his own. I used a 2x9V/30VA toroidal transformer (this one, sorry, page is in French Wink : http://www.stquentin-radio.com/forums.html?page=info_produit&info=6591&color=9&id=0&act=0)

I made it 9-0-9 by connecting one wire from each to get a 0v center tap, but added no extra circuitry.

It works and the units (MP 2016A and XP 2016A) light up and function correctly, except for a background hum which my friend says it wasn't there before.

The hum exists even with volume to zero, and doesn't get louder when turning the volume up, but it is quite annoying...

Does this hum come from the PSU I made ? Is there a way to avoid it (by adding extra circuitry for instance? Or by shielding the PSU?).

The hum does't get beter or worse if I move the PSU closer to or further from the units, by the way...

Thanks in advance for your help!
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tupinamba



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PostPosted: Mon Jan 05, 2015 12:12 pm    Post subject: Reply with quote  Mark this post and the followings unread

UP ? Wink
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Blue Hell
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PostPosted: Mon Jan 05, 2015 12:36 pm    Post subject: Reply with quote  Mark this post and the followings unread

You may have connected the wrong secondary wires? I would expect you'd have to connect a black to a red one .. if those are actually the colors you have ...

You can check .. when you did it right and do an AC voltage measurement between the two '9' points you should read about 18V and not about 0V.

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tupinamba



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PostPosted: Mon Jan 05, 2015 2:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks, I will check this tomorrow! I might have gotten it wrong. So this could explain the fact that it works but still hums?
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Blue Hell
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PostPosted: Mon Jan 05, 2015 2:19 pm    Post subject: Reply with quote  Mark this post and the followings unread

Depends a bit on the PSU internally, but could yeah
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tupinamba



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PostPosted: Mon Jan 05, 2015 2:45 pm    Post subject: Reply with quote  Mark this post and the followings unread

OK, great, I'll check!
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tupinamba



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PostPosted: Tue Jan 27, 2015 8:15 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

I finally had the opportunity to check, and the wiring is correct : 18v between the two '9v' points (actually, it is 20v / 10v...)

But I think I know what's wrong.

I use this PSU to "daisychain" the mixer (MP 2016a) and the power amp (XP 2016a)

It reads in the RS-1 PDF sheet that
Quote:
"Daisychaining is acceptable only where balanced wiring is used exclusively, and the total current demand of all products being powered does not exceed the maximum output current rating."


I think where in the clear in terms of output current (1.66A if I'm right with my maths: I used a 2x9V/30VA toroidal transformer)

But if I unplug the PSU from the XP 2016a, then the hum noise disappears while listening to the MP 2016a.

So:
Do I have to make a second PSU for the XP 2016a?
...Or:
Is there a way to split and isolate two outputs from my single PSU using extra circuitry?

Thanks in advance...
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tupinamba



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PostPosted: Wed Jan 28, 2015 4:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

UP ? Wink
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tupinamba



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PostPosted: Sat Jan 31, 2015 4:59 am    Post subject: Reply with quote  Mark this post and the followings unread

Major Tom to Ground Control?
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Blue Hell
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PostPosted: Sat Jan 31, 2015 5:18 am    Post subject: Reply with quote  Mark this post and the followings unread

Drawing too much power could cause hum, yes. The bit where it says "balanced wiring" suggests that there may be grounding issues too .. I'd need to know more details to give a proper answer ... one could check with an oscilloscope for overload conditions ... the 2nd power supply option may be the easiest way out when you have no tooling.
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tupinamba



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PostPosted: Sat Jan 31, 2015 3:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

Great, thanks for your answer!
Well, I do have an oscilloscope but I'm not very familiar with its use... How do I check if it is overloaded?...

Thanks,

Gaël
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Blue Hell
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PostPosted: Sat Jan 31, 2015 4:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

Look at the DC with the scope set to AC and when it does not look like a straight line but it has dips in it at a repeat rate of 50 or 100 Hz the load is so heavy (relatively) that it probably would cause hum.

You may have to zoom in a bit (less Volts/Division) to see it (like 1V/Division or 100 mV/Division).

A suitable time base value would be around 10 ms / Division.

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tupinamba



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PostPosted: Sat Jan 31, 2015 4:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks! I'll try that.
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tupinamba



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PostPosted: Sun Feb 01, 2015 3:44 am    Post subject: Reply with quote  Mark this post and the followings unread

I found a guy in Japan who has made tons of mods on a Rane MP2016a and XP2016a, including a new power supply :

Posted Image, might have been reduced in size. Click Image to view fullscreen.


Posted Image, might have been reduced in size. Click Image to view fullscreen.


It has a very big transformer + extra circuitry (but I wonder if the extra circuitry isn't a mod where he withdrew the caps from the modules and put new (better) ones directly in the external PSU)

I'll check my PSU for overload and we'll start from here!

Also : I'm planning to change the capacitors inside the modules as well, like the guy did.
I'll change the miniaturized electrolytic caps with Nichicon Muse (non pola) and Elna Silmic II (pola).
Should I also change the film foil caps (who look like standard MKT, see picture below) with Wima FKP2?

Thanks again, and I'll post as soon as I'll have tested my PSU for overload!

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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