EA Tremolo - PCB Testing

Now that I have the PCB all ready to go I will head back to my prototyping contraption to ensure that every thing is working properly.  I attach all of the PCB wires to their respective connections on the pots and jacks.  Picture of the PCB being tested.

Although messy and tough to see, you should be able to make out the green LED on the right side of the breadboard.  Just trust me when I say that it was blinking.  I connected everything up but when I plugged a guitar in and tried to play I just got an unpleasant constant buzz.  My first thought was a grounding problem.  I checked my connections on each grounded component and nothing seemed to be wrong.  I then brought out a very simple tool a made about a year ago called an audio probe.  For anyone building/repairing/dabbling in audio circuitry I will highly recommend he/she to take the small amount of time needed to make one of these.  It sounds cool but is insanely easy.  All an audio probe is a standard 1/4" guitar cable but snip off one end, strip the ground and lead wire, and then attach either wire or probes to each and following the signal path of your guitar within a circuit.  Some people like to put a capacitor in their audio probe but I haven't seen the need for one yet.  I clipped the ground wire of the probe to ground and started probing around at my guitar's input to see how far in the circuit I had to go before the circuit disappeared.  Luckily for me, it wasn't long at all.  I didn't even reach a component. I tested on the the guitar's input cable itself and everything worked fine which was relieving.  I then tested the alligator clip that was attached to the tip pin of the input jack.  As I expected, the alligator clip wasn't at fault.  I then tested the contact point where the input wire is soldered into the PCB.  This is where I got no sound.  The wire I use is often salvaged from old electronics and varies in gauge and age.  I probably should have used a different wire when i first wired this connection because I remember thinking that it seemed kind of thin and weak.  I was excited though there was no time for intelligence.  The problem with the wire was that the insulation had melted at the solder joint.  I had already known this before I tested the PCB.  I thought I was doing some pro soldering shit though because the insulation had melted down onto the PCB and covered the pad.  I thought I was a baller and had accidentally insulated a pad while soldering a connection.  Turns out I was still a massive noob and that the insulation had also melted down the wire through the pad's hole preventing the wire from contacting the PCB.  I replaced the wire with a better and thicker one and then everything worked just fine. This meant all the hard parts were done.  All that was left was to prepare my enclosure, wire the offboard components, and assemble!

EA Tremolo - PCB

So I got the breadboard working all fine and dandy and moved on to wiring up the PCB.  First I start with the low sitting components, in this case, just the resistors.  Below is the board wired with only resistors in it.

Notice the one resistor that was wired vertically.  This is because in order to put two wires on the board for the LED it was required that I put that resistor in vertically to allow access to the pad I need for a wire. In the picture I actually still managed to put one of the leads of that vertical resistor in the wrong pad but realized my mistake later when it came time to install the LED.  Next come taller components like the transistor sockets and the non-polarized caps. (Picture only shows the sockets)

Then the electrolytic caps to finish out the board.  Snip off the leads on the back and that is it for components.

Notice that the spot for a 1k resistor is left empty.  Had I not opted to go with the blinking LED mod these pads would be used but since I decided to change things I no longer need that resistor. Once all of those components are wired up I solder in all of the wires, plop the transistors in their sockets, and that is all we need to do with the PCB.  Completed PCB (minus ground wire) shown below.

The layout I followed from generalguitargadgets.com is shown below

EA Tremolo - Breadboarding

Upon receiving the parts from Mammothelectronics.com my first goal was to build up the tremolo circuit on a breadboard from a schematic.  The schematic I followed is below:

I had breadboarded circuits before and decided to build a sort of pedal/circuit prototype creation that would make it easier, especially when building pedals, to breadboard circuits.  All it is is a piece of wood that I attached three panels of acrylic to three sides of the wood.  I will make another entry showing what I'm talking about by itself. Anyways, it took me about 5 or 6 attempts to get the circuit working on the breadboard.  I was unfamiliar with orientating transistors, specifically non-PNPs, and am pretty sure that my mistake every time until I got it working was that I had transistors in the wrong way.  Although it didn't sound good, and something seemed off, I did get it working.  Below is a picture of the working circuit on my breadboard prototype thing.

This was before I added the LED indicator.  I just wanted to get the audio working at first.  I then wired in the LED and noticed some problems.  The LED worked and responded to my turning of the speed knob but once I maxed out the speed and tried to decrease it the LED stayed on and did not start blinking.  The depth pot also seemed to have no impact on the sound when turned.  Luckily the first thing I thought of was the problem.  As seen in the picture I was using a 9v battery to power my circuit.  I had used this battery many times before and questioned how well it was performing after all this time.  First I measured the DC bias on Q4 to assure that I was getting close to 4.5V.  I was not. The voltage over both 1M resistors that connect to Q4's gate were well short of 4.5V.  I then measured the battery's voltage and got something around 5.6V.  Not good.  So after swapping out the old battery with a fresh 9V, I remeasured and tested and everything was sounding great. The LED was responsive to all of my changes in speed and the effect of the depth knob was very apparent. Excited, I went and got the PCB to start wiring everything into place.

EA Tremolo - General Guitar Gadgets

This is the first project I will record on this blog.  I am attempting to build an EA Tremolo effect pedal based off of the information and PCB provided by generalguitargadgets.com.  I ordered all of the components for this build off of MammothElectronics.com for roughly $30. Could have gone cheaper but I preferred to spring for quality jacks, pot dust covers, and other unessential expenses to ensure that the build would go smoothly. The 1590B enclosure came from eBay costing $6.73.  The PCB was ordered from generalguitargadgets.com was $15 total. I had all other tools and parts on hand already so I would rough this project out to be just over $50.  I decided early on that rather than having a basic on/off indicator light I wanted to do the modification that would allow an LED to serve as both an on/off indicator and flash (more of a swelling glow) in time with the tremolo's speed.   This was a very simple mod that required only changing one resistor value and adding a wire to the PCB.  I also wanted to replace the metal baseplate with a piece of acrylic and keep all LEDS internal so that instead of seeing an LED on the top of the pedal, the base would glow in time with the tremolo speed and let me know when on or off.

Zweeno

This blog's main purpose is to serve as a type of journal that I can record my projects in.  I never remember to record anything I do in any written form so this hopefully this helps solve that problem. I've chosen my "brand" name to be Zweeno.  Why? Because it is a mixture of my first and last name and sounds neat-o.