Toroidal Power Transformer PSU mod on Nava 909 Clone

[hofmann]

Hi, I'm new to this blog so go easy 

I have started my 2nd SDIY (Synth DIY) project. The Nava 909 Clone by e-licktronic http://www.e-licktronic.com/en/content/46-nava-roland-tr-909-clone

My first was the RE-303 (TB-303 Replica) http://www.dinsync.info/2015/10/re-303-its-not-clone-its-replica.html

AND I'm addicted! 

Anyway, I wanted to get some advice on modding the PSU to have a nice Toroidal Transformer in the nice metal box I have bought.

I have found this http://imgur.com/a/IeBch#4 & http://www.e-licktronic.com/forum/viewtopic.php?f=16&t=331 which is some good advice on the same mod but on e-licktronic's "Yocto" 808 Clone.

It looks simple enough.

BUT, I wanted to get some SOLID advice on if this will work on the Nava. The PSU circuit looks fairly similar...

This is the Yocto PSU MOD;


This is the Nava PSU Schematic;


AND Full Nava Schematic http://www.e-licktronic.com/en/index.php?controller=attachment?id_attachment=48

Will the mod work for the NAVA? Or do I have to Modify something. Both kits specify 15v AC 1000mA Wall Wart Transformer.

I have this Toroidal Transformer from mouser http://au.mouser.com/Search/ProductDetail.aspx?R=VPT30-830virtualkey55310000virtualkey553-VPT30-830. I don't think it has a center tap?!

I also want to use the "loop Breaker" Circuit.

Is this good or is there a better solution?

Will this mod work? Any tips with Toroidal Transformer mods?

Thanks 

CREDITS jeroenbvo @ http://imgur.com/a/IeBch#4 http://www.e-licktronic.com/forum/memberlist.php?mode=viewprofile&u=437

[mariush]

According to the transformer datasheet, it has two separate secondary windings. You can connect them in series to get a center ground.
See datasheet : http://www.mouser.com/ds/2/410/VPT30-830-781532.pdf  - connect RED to ORANGE and that's your center tap, your ground.
you can then replace your 1n4004 with a standard bridge rectifier



C1 and C2 are your c5 and c7

[hofmann]

Hey mariush, thanks for the zippy reply! 

Ok so using the NAVA schematic


I would do this?



Then I want to add the Ground Loop Breaker?
2 x 1N54xxx
1 x 10 Ohm 5 Watt
1 x 100nF for filtering RF noise



Where would I add this?

[hofmann]

 

[hofmann]

Wait a minute.

The device requires AC not DC.

So no need for the Rectifier

[mariush]

I don't know about that ground breaker thing and I'm too tired to think about it.

you could connect the D11 diode directly above the diode of the bridge rectifier (basically directly at the wire from the transformer. No sense in adding another diode in series to have two voltage drops until the power goes into that LM2596
The LM3596 is a switching regulator, it's used to convert 15v+ to 5v at some high current, no clue how much.
The +15v and -15v linear regulators are probably for low current, for opamps and other such uses, i guess maybe below 100mA on each.

If your transformer is not big enough (and because that winding is shared with the 15v linear regulator), the voltage of the input of that regulator IC may go down too much if you're not careful. To prevent that, I would also increase the 680uF 35v to something like 1000-1200uF 35v if it's not inconvenient and if there's room.

You may not need a bridge rectifier but it's space saving and simple to use .. for example : http://uk.farnell.com/micro-commercial-components/mb110s-tp/bridge-rectifier-1a-100v/dp/1924377 (nice DIP package,easy to put on a prototyping board, you have AC inputs on one side and + / - on the other)  or something like this : http://uk.farnell.com/vishay/gsib1520-e3-45/bridge-rectifier-15a-200v/dp/9549684
Alternatively, you could also build a bridge rectifier out of 4 diodes, and then you could do better by using diodes with smaller voltage drop than 0.7-1v you see on 1n4*** .. mabe use something like 1n5818 or other schottky diodes.

[hofmann]

Ok now I'm confused.

Why do I need a Rectifier?

"So, two ways to go, either remove D1 and D2 and replace it my a bridge rectifier, or go less intrusive and just add 2 more 1n4004 diodes to D1 and D2.
This way you change the PSU into a full wave bridge."

From; http://www.e-licktronic.com/forum/viewtopic.php

[hofmann]

Whats the benefit of both of these? Bridge Rectifier or Wave Bridge?