DIY Pedal Attempt

[whitebison66]

I wanted to start this... process here, since I 'know'  people.

I have owned and used (and liked) the Chandler Tone-X, which gives you the Schenker 'parked wah' sound.

I was thinking about installing one into a pedal so I could use it on all my guitars. I thought it would be a good place to start getting into DIY pedals.

I know there are a lot of sites that talk about DIY pedals, but I thought I'd ask people here if they recommended any sites more than others.

Where would you point me to start learning about how to, for example, move the on/off function from the push/pull pot to a footswitch, or wire the AC jack to the circuit?

For that matter, is this something I can do from scratch without using a Tone-X?

I also realize that I could just use a wah pedal, but I really like the specific tone the Chandler gets.

And I've already thought up a cool paint scheme for the box.

I found the empty pedal, and I am sure I can get all the components locally here in Hong Kong. I just need some help with the particulars.


As always, thanks in advance!

 

[Patrick from Davis]

I am not familiar with the circuit that you are talking about, but the questions you are asking are not that difficult to answer.  The switch on/off is easily done with a DPDT switch.  TPDT if you want an LED to show you it is on.  The on/off of the battery is done easily with a stereo plug that is wired so that ground is in a broken circuit until the cord is attached to the plug, completing the circuit.  There are also components that you can get that have the 9 V wall wart in that are mechanical switches so that the battery is taken out o the circuit if a wall wart is plugged in.  All of these modifications to the original circuit are rather minor at best, but take a little getting used to to "see" it right.  Still if you have the circuit, it is easy to stuff it into a box and use it that way.
Patrick

 

[mayfly]

You can definitely do this from scratch.  Just get the schematic of your favorite wah, mount the pot to the front (as the sweep control), hook up the footswitch and there you go.  Things like LEDs, true bypass and power jacks are very simple.  I or several others can help with that.

 

[whitebison66]

Thanks guys! I will try to find the 3PDT and other parts today, updates to follow.

The 'electronics neighborhood' here, Sham Shui Po, will be crowded, since its Sunday (and its Hong Kong), and its currently 32C/90F, with a 'feels like' adjustment of 37/99. 

But it's for GUITAR STUFF!!!

I'll try to take some photos of the trip, in case anyone is interested.

 

[whitebison66]

I ventured out into the crowds, heat, and humidity Sunday to see if I could find parts for this project. Sham Shui Po is not as clean, big, or covered with maid cafes as Akhiabara, but the prices are better and I speak more of the language.

I went to Sham Shui Po armed with a list of parts, a couple of photos, and very basic Cantonese skills. People tell you everyone in Hong Kong speaks English. Those people don't live in Hong Kong.

I went to Ap Liu St., which is lined with stores selling all manner of electronics stuff, and the street itself is lined with stalls selling parts and accessories. I bought a bike recently, and found all the lights I needed as well as a Camelbak knock-off on Ap Liu St. for very little $.

I headed to a place where I usually go, because it has a huge selection of parts, connectors, cable, etc. I figured it would be as good a place to start as any.

I found 2 '125b' enclosures (Phase 90-size) for HK$50 each. I found input jacks for HK$8, LEDs for HK$5, and power supply plugs (brought a connector cable with me to be sure) for HK$5. In the packages of smaller parts, there's 2 in each. So I have enough to make 2 pedals!

Total HK$118/US$15.14.

I struck out on the 3pdt footswitch, but ordered some today on eBay that are just over the border in Shenzen; US13.50 for 3. I've ordered from this company before and never had a problem.

I am thinking of using the 3rd switch to put an LED into my Crybaby 535Q, but that's a ways off.

The Tone-X was already in my parts box, as was the wiring diagram.

I am hoping I can recycle the pot from the Tone X, once I figure out how to move the switching function from it to the 3pdt. If not, I'll have to get another one.

But it was fun getting the parts, and it makes me think I can actually do this, so that helps.

More updates after I get all the parts!

 

[mayfly]

Pretty cool. 

From looking at the board of the Tone-X I'm guessing that to disable the DPDT switch you'll need to pull the pot out of there.  only then you'll have access to the PCB pads for the switch.  BTW, you may be able to re-use the pot using flying leads to hook it up if you are careful.

Do you have a schematic of the toneX itself?  you'll need it to figure out what parts of the switch do what.  Once you have that it will be easy work to hook up the 3PDT switch to the PCB and to your little LED.  BTW - what's the current rating on the LED?  You'll need a resistor to drop the current down so you don't fry it when it's connected to the battery.

Trevor

 

[whitebison66]

My plan is (was?) to replace the 9V battery adaptor with a plug, so I could run it off the Dunlop Brick.

The LED rating is something I'll need to look into, since I didn't know.

This is the best image I could get of the Tone-X. The green wire on the actual unit has been re-Painted yellow, since the original yellow wire broke and I had none when I replaced it, hence the green. I hope that makes sense!

 

[whitebison66]

I was going to put the LED onto the 3DPT; does that make a difference?

 

[mayfly]

I was going to put the LED onto the 3DPT; does that make a difference?

Nope.  You'll still fry it at 9V.  Here's a quick tutorial:

Diodes (and LEDs) are silicon devices that don't conduct in one direction, and are free to conduct in another.  In the conductive direction, they have a small voltage drop (more on this later) and a fairly small impedance.  They have limits to the amount of power they can dissipate when conducting, depending on the construction, package, etc.  This limitation is specified as the maximum forward current of the device.  For a LED it's usually in mA.  

When an LED starts to conduct, there is a diode voltage drop of about 1.4V.  If you hook this up directly to a 9V source, as much current that the supply can source will be dumped through the LED - until the device fails (which will happen very quickly.  About a second or so).  So... you use a current limiting resistor.  Let's say that your LED has a max forward current rating of 20mA (the spec for the Kingbright WP7113syc).  If you aim for 15mA, here's the calculations you'll need to figure out what resistor you'll need:

Resistor voltage = 9 - 1.4 = 7.6V
Resistor current = 15mA
since V = IR, R = V/I, so the resistance you'll need is:
7.6 / 15mA = 506 ohm.  510ohm is the closest standard value.

Slap one of these in series and you'll have a nice bright LED that does not burn up on you.  YMMV depending on the specs of the LED you have.

 

[Patrick from Davis]

510 ohm?  Wow, that is a small one.  I am used to a 4.7K resistor between the the LED and the battery, at least for a 5 mm LED.  3.3K if you want it to blind the person using the pedal.  But I suppose you are right, it depends of the LED's rating.

Something I forgot is an LED holder like this. 

It will hold the 5mm LED in a 1/4" hole (approx size of the hole) in the box so that you don't have to mess with a way of securing it.
Patrick

 

[mayfly]

all depends on the spec for the LED.

 

[Patrick from Davis]

I was going to put the LED onto the 3DPT; does that make a difference?

Yes.  LED's tend to be noisy electrical devices.  You give it a separate leg on the switch to keep it from making noise in the audio circuit.  So on the 3PDT switch, on one set of legs, you have 9V in and then a resistor, then the LED, and tie that to ground.  The other two legs are used for input to the effect, and from the effect to the output.  When the switch is pushed then there is a wire between those two legs to bypass the effect.
Patrick

 

[whitebison66]

Parts update; the 3PDT switches are here.

I also bought some 510 ohm resistors, two types whose difference escapes me (as does the reason why I got photos of the blue ones and not the brown ones).

The LEDs are 5mm, and I bought some plain and others in protective 'sleeves.' Overbought so that I can experiment (read: make mistakes).

So I guess its down to the actual wiring part, or at least starting to solve the LED/resistor thing, then on to the swapping of wires on the Tone-X.

Wish me luck!

 

[Patrick from Davis]

The blue ones are metal film, the brown ones are carbon comp, the beige/tan ones are carbon film.  There is mojo associated with each.  Carbon film tends to be considered the cheapest, and metal film is usually the audio grade stuff.  Carbon comp is the vintagy ones.

For the LED, it doesn't matter.  You are not part of the audio path there, so the tan ones are fine.  If the 510 ohm resistor is too small, you will let the LED's smoke out.  It smells quite bad when this happens.  I have personally experienced this.  Not the greatest smell.

I see you got the 3pdt switches.  Here is a picture that has a way to wire them (bottom right).  There are at least two ways people wire these things, either work, I've tried them both.

Good luck
Patrick

 

[whitebison66]

Patrick and Trevor, thank you both! This project is starting to seem more and more doable.

The resistors are (according to the receipt), 1/2 and 1/4 watt, not sure that makes a difference. I'll need to really make sure of the wiring of the LED, but that's why I got so many of them.

Hopefully this weekend I can get some work done on it, but we'll have to wait and see!

 

[Patrick from Davis]

The wattage will not matter for the LED.  They don't pull much current.  The 1/4's should be smaller if you are hurting for space in the encolsure.
Patrick

 

[mayfly]

Just to expand on that, the wattage rating of the resistor is the max power it can dissipate.  for your purposes, power is P = V * I.

Going back to our original example (which BTW may not at all match the LEDs you have), the drop across that resistor is 9 - 1.4 = 7.6.  The current is 15mA.  so the power that resistor must dissipate to the air is 7.6 * 15mA = 114 mW, or 0.114 watts.  A 1/4 watt resistor is fine.


BTW, regarding those wiring diagrams, usually you want to run the power through the same pole of the 3PDP that the LED is run through.  This is to turn the unit off when it's not being used.  If you are using an adapter, you may not care.

 

[Patrick from Davis]

I have never used the 3pdt switch to turn the power on or off on a pedal.  Just the effect on or off.  What I have always employed is a stereo jack on the input.  The tip is the signal in, the ring (the middle guy) is the (-) from the battery, and the sleeve is the ground from the circuit board.  The (+) from the battery goes straight to the circuit board.  When the cord in plugged in the grounds are connected, and the pedal is on.  This keeps the LED isolated from the rest of the circuit, because they have historically been associate with a lot of electrical noise.  This is also why you burn through batteries if you leave the pedal plugged in.
Patrick

 

[mayfly]

  This keeps the LED isolated from the rest of the circuit, because they have historically been associate with a lot of electrical noise. 
Patrick

Just for my own education, where did you hear that?

(BTW - I completely disagree, but I'm too polite to say.  A LED, just like any other diode, will only generate noise when it's being used to rectify (i.e. it's got AC being put across it).  Remember, LEDs are used in the signal path of many pedals out there, including some famous overdrive units.

 

[Patrick from Davis]

The DIY pedal forums run rampant with that kind of speak.  BYOC, Geofex, DIYstompboxes...  For those guys it is dogma.
Patrick

After looking, trying to look busy at work and failing, I can't find a reference to it anywhere.  When I started making the things I couldn't go a post or two without tripping over it.  And yes, I do know that the diodes are used in several OD/Dist pedals for clipping purposes, as well as many other purposes.  I guess I might have a crossed wire upstairs, but I was positive about avoiding those in the audio circuit and the switching.  Oh well.  Also, I have never seen a pedal turned on and off with the bypass switch, so that struck me as odd.  Quite honestly, it doesn't matter if it works.  If you have the 3PDT switch, it is easy to wire up the LED as shown in the picture I posted.  That is the common diagram I am used to seeing, so I posted it.
Patrick