POWER SUPPLY WITH NOISE

[Rhandy]

Hello!

Yesterday I try to build one power supply like this one.  http://www.instructables.com/id/Build-A-Power-Supply-For-Your-Guitar-Pedals/



I add 2 more LM7809 to circuit and 2 more 100uf Capacitors.

My test Board

First part, including AC/DC. rectifier bridge and first 3 capacitors of circuit are mounted apart.

Front

Back

All plugs are connected with common (-) in daisy chain. 3 plugs have separated 9V , one per LM7809, and other 2, 12v and 5v.

3 Lm7809 gives me 8.91v, 8.92v and 8.96v.

When I connect to my boss TU-3 and My Zakk Wylde Wha Wha on front of AMP (ENGL E650) with lead and high gain, I dont have any "anormal" noise, but when I plug In effect lopp MXR carbon copy and Boss Rv 6, I have lots of noise.

Any suggestions please???

[garcho]

sometimes digital pedals (which can often draw more current than analog) can get goofy with a switching power supply, some don't like sharing the PS with other digital pedals either. the chain that's giving you problems is the digital chain. in a set up like yours, you have to try each and every pedal individually, THEN see what happens when they're in a signal chain.

[Rhandy]

Thanks for your answer.

I try it before. Boss TU-3 and Wha in front of amp And MXR Carbon Copy in loop = No Noise.

Dreamtheater pedal don´t like power supply, Always give high frequency noise, in front or back.

I if plug other power source to boss RV-6, I dont have noise in Loop.

[antonis]

IMHO, 18V secondary is an overkill..!!

It gives more than 24VDC after rectifing and smoothing, so your IC's have to handle a voltage drop from 12 up to 19 Volts..

[Rhandy]

No. After rectifier bridge I have 14v dc.
But I think I found issue.
Is one of lm7809. Because if I plug in other 2 outputs I dont have any hi ffrequency noise. I change cap in front of that lm7809 and I still have noise. After that I change dc output from others lm7809 and No noise.
Tomorrow I buy one new lm7809 for replace that one.

[ElectricDruid]

14V DC to supply a 12V regulator sounds about right, but you will find that the 5V regulator gets noticeably hotter than the other two because of all the extra voltage it has to dissipate as heat.

I've had the same thing in a power supply I built for a synth project. That had +/-15V rails for the analog circuitry, plus +5V and +3.3V rails for the digital circuits. The 3.3V regulator gets *hot*, and the +5V one gets warm, whereas the other two never seem to warm up at all. I decided that if I build another, I'm going to use a separate transformer for the lower voltages. It's possible that someone somehwere makes a transformer with suitable secondary windings, but it's probably easier to just use two, even if it gets a bit heavy.

Tom

[Rhandy]

Hi ElectricDruid

You are right. I  removed lm7905.

[antonis]

After rectifier bridge I have 14v dc.

Then there are 2 cases:

1: Your secondary isn't actually rated at 18VAC

or

2: You OVERLOAD your transformer..!!

Any secondary voltage is much higher than it's rating with no load and it starts to approach it with loading...
(the more the current - the lower the voltage)

If you don't exceed it's maximun current rating, which in your case is 300mA, you'll get the 18VAC which in trurn will be 24VDC..            (18 times 1.41 minus 2 diode voltage drop..)

If you indeed measure 14VDC something is going wrong..