Charge Pump, losing -9v supply

[MAO]

Ran across something new today, looking for some advice/experience.

I built the Craig Anderton Phase Shifter using a TL054 charge pump to supply the +/- 9vs.

Madbean Road Rage 
CA Phase Shiter 

The Phase Shifter was working, but just didn't sound right. It turns out the -9v supply was only -0.7v. No shorts or anything, but I found when I removed either TL074, the negative voltage would jump to -7.3v. Removing the TL071 had no affect on the negative voltage.

I then remembered reading something about decoupling caps at the +/- pins of the opamps (page 14 EN 04/1997) so I added a 1 uf monolithic cap from pin 11 to ground on one of the TL074s and the -7.3 voltage came back. I then tried a 10uf, with positive leg to ground and the voltage went to -8.3.

Is this a know issue with charge pumps?

And is there a "proper" way to filter the supply lines of a charge pump when connecting multiple ICs or higher current circuits?  

[ξεναγος νεκροπολης]

omg!

for 10 days now i'm working on a similar problem.
so...i'm sorry MAO! i can't help you on this one...but i hope i could get some answers too from the experienced, without starting a new thread.

i've build my layout for rustbucket,
http://guitar-fx-layouts.42897.x6.nabble.com/rustbucket-2015madbean-tp26020p26171.html
using 13700 in place of both 3080, and i have problems with the supply.
i get the +15v, but i can only get -7v

i believe that for small projects, all these cute charge pumps work nice.
but for the big ones, i want to be able to eliminate any instability related with the supply

i'm working on an idea that will use a transformer.
from 220v ac, i want to get 18v dc, and with 7815 and 7915 make the +/-15v. i got some small transformers out of old cpus, old amplifiers and staff like that, but i'm still afraid of those 220v ac.
is there someone that could point out a solution for my problem?

i also what to be able to get much more than 100mAmps out of that thing.

this is how my transformer looks like

it has 3 lugs from one side and 2 from the other.

thanks in any advice!
Savvas

[Ciaran Haslett]

The 2 pins will be your primary side (mains voltage) and the 3 will be the secondary.  You'd need some specs of your particular transformer...but you'd be looking for 220VAC Primary and 18V-0V-18V Secondary.

Then you'd need to rectify its output, either by using a bridge diode setup or a self contained rectifier.  Here's a setup using a diode bridge which you probably have in your parts stash.

The centre tap on your secondary becomes the circuit ground.  The + out of your bridge is your + supply and the - is your - supply.

The amount of ripple filtering can be left up to you.  I've seen schemes with tons of filtering and some with very little.

You'll then need to plug in a 7915 on the both supply rails (79xx for the higher output current you're looking for) then maybe filter the outputs of these as well.

A few considerations...

1. Use a fuse on the primary side.  If anything works loose the fuse should protect the transformer (and you)
2. If using a metal box, ground your enclosure to the mains earth and isolate your circuit ground (including In/Out jacks)
3. Build this as a separate PSU.  Apart from making a pedal massive with this inside, the EMI from the transformer would probably cause significant noise.
4. If using this to daisy chain multiple dual supply pedals, consider putting fuses on the regulator outputs too.
5. Depending on its use, consider heatsinks on the regulators.


All in all, working with mains isn't any different than working with low voltage DC, it's just not forgiving.  So quadruple every single connection you make before you power anything on.