Hello, I'm in need of expert help.
So I've come across a old rack mixer that I need to put to use.
Problem is that it was part of a complete system and power came from sub woofer box as well as the signal, there was a power adapter for this back in the day to use the mixer as standalone. But not for sale anymore obviously, so I guess I will have to build my own.
I will try to give the all the information I could find, and hope that someone can help me with this.

The mixer: Viscount Micromix

link to the complete system manual:
https://www.yumpu.com/en/document/v...no-inglese-voice-system-factotum-musicyocom/5

Schematics are in the PDF attached.

In the back, on the power input, theres only one label AC 17-0-17 (sorry forgot to take a photo to the back side.)
I'm guessing 17V positive -17V negative (34V AC)

Thank you guys in advance!

 

In the back, on the power input, theres only one label AC 17-0-17 (sorry forgot to take a photo to the back side.)
I'm guessing 17V positive -17V negative (34V AC)!

Close. but not positive and negative. The input is 34 Vac center-tapped. With the center-tap connected to the system ground, this yields two 17 Vac voltages that are 180 degrees out of phase. I agree that finding an exact match will be difficult, but there are other ways.

Check F1 and F2 to see if they are 800 mA or 1800 mA (1.8 A). The schematic is not clear. A transformer with either a single center-tapped secondary or dual independent secondaries that can be combined for somewhere between 16 Vac and 19 Vac per phase will work. Mounting it in a small box with a line cord, switch, and output cable is a weekend project.

* * * * for supplying the schematics with the question.

ak

 

Hello,

@AnalogKid , The fuses are T 800 mA (800 mA slow blow):



Bertus

 

Ok, i'm kinda on the dark here,
Something like this:

10W EI Ferrite Core Input 220V 50Hz Vertical Mount Electric Power Transformer

or maybe this? (looks the same to me)

Trafo Transformator Netztrafo Ringkern 2x 115 Volt --> 17,5-0-17,5 Volt 0,5 Amp

 

One of them has 4 wires and the other has 7, so they're not the same. Where are you located?

Is there a label on the back of the unit that says what the input current or power is?

ak

 

The second one should work, as it has 17 0 17 . Just a little lean on the 5 amps. I would try, can't hurt anything. Just 3 regulators. Check tag as an log kid suggested

 

Is that 5 amp or .5 can't see the transformer to we'll on my phone

 

above the pic was the link to the sellers product

 

The toroidal transformer will work ok.
Just be sure to connect the 2 primaries in parallel the correct way for 120V, or in series, once again, the correct way, for 240V.
If you are not sure how to do that, just ask for some help.

 

My search turned up https://www.digikey.com/product-detail/en/triad-magnetics/F-354X/237-1980-ND/5032195

 

Hi again guys, thanks for the input!
I live in Portugal.
I'm still kind of confused in what type (which terms to use for searches) but I got the picture... I think.
As long as it is somewhere between 2x16v and 2x19v or single 32v and 38v I should manage to work it out.
Now I'm left with the question... current? 10w? 5va? what should I be looking for here?

 

Hello,

You would need a center tap transformer of minimum 30 VA.
One side of the transformer goes to pin 1 of the connector.
The center connection of the transformer goes to pin 2 of the connector.
The other side of the transformer goes to pin 3 of the connector.

(for the connections see post#3)

Bertus

 

wow 30va... I was looking at transformers around 6va... hehehe this is going to cost me more than I though!
Found a UK seller with a myriad of choices... going to look at it!

 

The toroidal transformer will work ok.
Just be sure to connect the 2 primaries in parallel the correct way for 120V, or in series, once again, the correct way, for 240V.
If you are not sure how to do that, just ask for some help.

The toroid also has less stray magnetic flux - quite handy if there's sensitive signal lines in the vicinity.

 

Ok, time to choose
Could not find any bargain :/

links (all 2x18v 30va):

R type on aliexpress 20€ (china - 20days delivery)

Chassis mount on aliexpress 19€ (china - 20 days delivery)

PCB on ebay (also on aliexpress) 17€ (spain - less than 3 days)

Toroidal on ebay 22€ (uk - less than 7 days)

I will wait for your wise advice to complete the purchase.
thanks again guys, learn a lot about transformers on this quest!

 

Ok, time to choose
Could not find any bargain :/

links (all 2x18v 30va):

R type on aliexpress 20€ (china - 20days delivery)

Chassis mount on aliexpress 19€ (china - 20 days delivery)

PCB on ebay (also on aliexpress) 17€ (spain - less than 3 days)

Toroidal on ebay 22€ (uk - less than 7 days)

I will wait for your wise advice to complete the purchase.
thanks again guys, learn a lot about transformers on this quest!

If you go for the toroid - don't make shorted turns strapping it down.

Usually a single stout bolt up through the middle. You need soft mounting washers so the surface windings don't get cramped/chaffed - the top washer needs to be backed up with a big "penny washer" to stop the padding pulling through the middle. Fill the space around the bolt with something non conductive so it doesn't go sideways if the unit is dropped.

 

Ok guys, saga is complete, end up buying:

BREVE TUFVASSONS TTS35/Z230/17-17V
Transformador: toroidal; 35VA; 230VAC; 17V; 17V; 1,02A; 1,02A; 0,5kg ROHS

12€ plus transport

Will do the follow up, but for now... THANKS for your patience!

 

Hello,

That one would perfectly fit the bill.

Bertus

 

Ok guys, saga is complete, end up buying:

BREVE TUFVASSONS TTS35/Z230/17-17V
Transformador: toroidal; 35VA; 230VAC; 17V; 17V; 1,02A; 1,02A; 0,5kg ROHS

12€ plus transport

Will do the follow up, but for now... THANKS for your patience!

That looks pretty sound.

 

Good choice. It does have two separate 17 volt windings, so will have have to connect these in series aiding. Looks like they are coded - banded red to pin 1, unbanded red and banded yellow to pin 2, and unbanded yellow to pin 3. Meter should show about 34 vac between pins 1 & 3.