Fundamental Problems! Any help would be greatly appreciated

[RockGuitarDude]

Ok, I've tried to build a bunch of things from treble boosters to tube screamers to a simple gain stage.  I can't get anything to work.  I know what I am doing to a certain extent.  I'm in my second year of engineering courses, so I have a good knowledge of how things work.

I think I am messing something up on a very fundamental level.  I've been building things on a plug board.  One of the things I don't get is where the ground goes and where the grounds of the inputs and outputs go.  Also, is it totally necessary to use a stereo jack on the input to get it to work?  I understand you need to do this to switch the power on and off upon plugging it in, but for now I just want it to work.  Recently I tried building a gain stage with a JRC 4558 and it started getting hot.  Is this normal?  If not, why is this happening.  I supplied 9V negative and positive to the respective terminals.

Thanks everyone.

[davebungo]

For most guitar effects circuits, you should only need to supply a single  +9V supply.  Forget the stereo jacks for now and concentrate on getting your circuits to work.  Your ground should be a common node between your input and output jacks and the circuit  ground itself.  Make sure you wire it as per circuit diagram and include any de-coupling caps as described and inserted with the correct polarity.  Can't think of anything else you could do that badly wrong.  Good luck!  BTW if devices are getting really hot then you probably have got a major problem with the supply wiring.

[H.Manback]

Grounding is pretty simple, getting it wrong though can prove to be a real pain in te goddamn ass... What you need to see is that grounding means making one bus for all the terminals that should be grounding. This comes down to just making sure all of them are connected to each other (not each point to each individual point of course :wink:).

Grounding on the input and output jacks needs to be done on the sleeve, that is the other part than the tip of the jack . Most schematics also have one of the battery terminals grounded. Make sure you ground the correct terminal. The switching part is not necessary, so stereo jacks are not required.

About that opamp running hot, it isn't supposed to do that. Assuming you connected the power to the correct terminals (battery + on pin 8 and - on 4), the only thing I can think of is you are putting too big a load on the opamp.
Just for the complete picture, you can make a opamp explode, if you have a power supply that can give enough current and you connect it incorrectly..

[bwanasonic]

What is a plug board? Is this a breadboard? Could the problem be the plug/bread board connections? Do you have a DMM for troubleshooting?
Is your plugboard wired like so?:

Code Select Expand


XXXXX - Bus 1
XXXXX - Bus 2

XXXXX
XXXXX
XXXXX
XXXXX
XXXXX
ABCDE


Where all Bus 1 Xs are connected together, Bus 2 Xs connected, Row A is connected together, etc. If you have a DMM, poke around to make sure things are really connected the way you think they are. If you study the wiring/layout diagrams at www.generalguitargadgets.com, you should be able to apply them to whatever you are building.

Kerry M

[niftydog]

ok, first you need to do some "dry checking".

before you plug anything into a new circuit, just run over it with a multimeter, checking for continuity of the connections and making sure there are no short circuits in the wrong places etc.

Measure resistor values out of circuit to make sure you're not reading them wrong.

Then, hook up the power supply and check for heat and smoke. If nothing is heating up, that's a start. Now check for appropriate voltages around the circuit.

Now, if everything is cool, hook up a signal and something to the output. If you're still having trouble, consider an audio probe or an oscilloscope!

a systematic approach will help you hone in on the errors.

[Transmogrifox]

If you've had electronics labs where you have to do this kind of thing, wiring circuits on the breadboard (plug board), you are probably familiar with the interconnections there.

The concept of "ground" was something I never fully comprehended until my 2nd year course.  Teachers just assume it's such a simple concept that there's no need insult your intelligence by telling you about it.

Just keep this in mind:  Current always flows from a positive to negative voltage potential.  A battery is not + and - 9V.  it has a 9V potential charge across it.  Your multimeter with measure +9V if you measure it one way, and -9V if you measure it the other way.  If you put a resistor across the terminals, "positive" current will flow from the positive to negative terminal through the resistor.

Now all you have to do is define one of those terminals as "ground".  If you define the positive terminal as ground, then all the voltages in a single supply circuit (that is operated from one battery) will be negative with respect to ground, therefore current is always flowing from ground to the negative terminal in this case.

If you define "ground" as the negative terminal (which is the common convention in single-supply electronics), then all voltages in the circuit are positive with respect to ground (except in the case of using a charge pump, or a capacitively coupled AC signal referenced to ground).

The moral of the story is that there is one common node where all circuit elements are referenced, and this is called ground.  It does not always physically connect to the ground pin in an outlet, or ultimately to a ground rod deep in the earth to make the circuit "ground" the same potential as the floor you stand on.  Often times I have clipped an oscilloscope probe to a circuit ground, then referenced it to a wall-outlet (earth) ground and seen a 2-3 V 60Hz sine wave.  It means either earth ground and the circuit ground are at different potentials, alternating at 60 Hz.  In that case, if you didn't have a good solid low -impedance connection to the grounding rod in the ground under the building, you would probably have a real loud 60 Hz hum in your audio path--one of the reasons for a "ground lift" switch on many amps and mixers.

I hope my rambling in addition to what others have posted helps you get a better idea of what is causing your circuits to fail.  I think when you understand the concept of "ground", your understanding of electronics and electrical systems will come together very quickly and all the loose ends that don't make sense will start to come together.

I'll admit that my knowledge in my second year of engineering was very similar to what you have expressed.  It was an awesome day when I got my first fuzz to work.  I designed it on PSPICE.  It sounded like sh**t, but it worked--audio in, audio massively distorted out.

I hope you'll get to experience that soon.  I think if you can get a single transistor amplifier to work, you'll be set for things like the TS and more fuzzes.

[Tony Forestiere]

Did you hack trough the traces not connected? :?