DIY Rat Clone Distortion Guitar Effect Pedal - The Dead RAT

Step 3 I love the smell of solder in the morning.......

This is always my favorite part. Following the layout on the PDF I always start with Resistors first. If you don't know how to read a resistor I recommend printing a chart off the web for reference so you can keep the values straight and not mix them up during the build. You can also set your Digital Multimeter to Ohms and measure them individually, if your resistors are 5% tolerance then the resistance for a 100 ohm resistor could be 95 to 105 Ohms and still be in spec.

Next I move to the Diodes and the Capacitors. Current only flows one way through a Diode so watch the direction so you don't install it backwards. Ceramic and Film Capacitors aren't polarized so they can be soldered in any direction but the Electrolytic Caps (round can looking ones) are polarized so make sure that are placed correctly or they could explode. (There is usually a stripe running down the side of the can with a "-" sign that corresponds to the Negative leg of the capacitor. The circuit board layout diagram always has a "+" sign on it where the Positive leg goes.)

Although not on the parts list, I bought an 8-Pin IC Socket for the LM308 so I could swap it out with other Op-Amp chips later if I wanted to do any mods without having to unsolder anything. You can get a set of 2 at the RatShack for .69 cents... part # 276-1995. After the components are soldered then precede to the wires. I bought a three pack of 22 gauge wire at RadioShack that comes in Black, Red, and Green so I could keep the similar paths color coded for a fool proof assembly.

Solder the Pots to the wires next, paying attention to the order (this is where different color wires helps out. I like to twist similar wire bundles together to keep things organized and keep them out of the way. Remember that in the wiring diagram the pots are shown face down so keep that in mind when soldering.

Alrighty, lets lay out the case and stuff in all together!

Comments

[streetcrab_helmut]

Could you plaase tell me how you got the top of the PCB printed (with the shapes of the components to be fitted)?

[silverHalo]

The component screen was just printed on some clear sticker material and placed on the board before adding all the parts.
Good luck.

[nellie18]

nice project!

anyway, if you mind, may i ask if how many watts you used on your resistors?
and how many volts for the capacitors.
thanks.

[silverHalo]

I probably used a mix of both 1/8 and 1/4 watt resistors. There isn't a whole lot of current flowing through the board so wattage isn't that important. 1/8 and 1/4 watt fit better than say a 1/2 watt resistor would.
The electrolytic capacitors need to be rated at least double the power supply voltage for safety. So for a 12 volt power supply you would use 24v caps or higher. You might get by with 12v caps but its always better to error on the side of caution.
Better safe that sorry.

[oelefante]

is there anyway i can make this work with a simple 2 pin switch? The 3pdt alone costs as much as all the other components together.

[silverHalo]

Not sure what you mean by a "2 pin switch", if you mean a dpdt (double pole double throw) switch then yes you can. The 3pole switch isn't much more than a double cost wise if you shop around. The 3rd pole is for turning the LED off and on, so if you use a DPDT you can just leave the LED out.

[bero2]

sorry for bombing you with questions but is that 8 pin ic socket one i could just pick up at the store or is it made especially for the lm308 chip

[silverHalo]

Just pick one up at the store (Radio Shack has them 2 for .99 last time I went). It is just a regular 8 pin DIN socket (DIN stands for "Dual In Line"). You don't need the socket if you plan to never change the LM308 chip. The socket allows you to experiment with other types of chips to get different distortions.

[bero2]

so it would be a good investment for the future right??

[silverHalo]

Sure, if you ever want to experiment then it is a good idea.

[bero2]

they have 1 for 48 cents at radio shack i think thats a good price for the option of experimenting...but for he future would i need to make any changes to the circuit  or does it not matter?and is their any chips you would recommend in the future? again sorry if they are not intellectual questions...thanks for all the help

[bero2]

are you sure those are 1/8 watt and not 1/4 watt they look a litte big

[silverHalo]

You are right, good call, it's been a while since I wrote this instructable... I zoomed in on the picture and can read the 1/4 watt on the packages. I fixed the error in the text. Thanks!

[bero2]

that makes my life easier i have alot of 1/4 resistors

[bero2]

could this project be done with only ceramic disk capacitors or do i need to get film ones too???

[silverHalo]

Well, It is better to build them out of film, mylar, or polypropylene capacitors since they offer better sound and less signal interference that the ceramic kind do. Also the film kind usually don't go down into the PicoFarad (really tiny values) ranges and there for the ceramic must be used. You could try to use all ceramic if you can find all the values you need, but it definitely will effect the overall sound.

[bero2]

ok thank you for the input ill get some film one today this is great btw...

[wowannoying]

how did you cut this from the others without breaking??

[silverHalo]

I assume you are talking about the circuit boards.... I either cut them in one of two ways.
With  a straight edge and a utility knife (with a disposable blade), I will score the board and keep running the blade across the line until it gets cut in two. Since the board is fiberglass it will dull the blade quite quickly, so I change blades often.
I have also cut them on my table saw if they are larger boards, but my favorite way is on a band saw since you can go slowly and have more control.