Help modding my crybaby

[SocraticTelecaster]

I'm planning on doing some mods to my Rev. E CryBaby, including modding it to true bypass, installing a yellow fasel inductor, and doing a vocal mod. At first I was just going to replace the 33K resistor in parallel to the inductor with one of a higher value, like 56 or 68K. But after viewing the stinkfoot page on modding a crybaby, I learned that you can replace the 33K resistor with a suitable high-quality trimpot (something like 100K lin), and that you can solder the trimpot in series with the existing resistor, which will guarantee that you never adjust it below the original value.

So that's what I'd like to do - install a pot for the vocal mod, with the pot wired in series with the resistor. The problem is, I have no clue on how to do that. I've built a number of pedal kits, and done a few mods, but I'm strictly a paint-by-numbers kinda modder. If I don't have a clear picture or picto-gram of what I'm supposed to do, I'm a bit lost. For instance, potentiometers have three lugs - but there seems to be only a need for two of them. But which 2 do I use, and where do I wire them? And how do I wire the resistor in series (I don't even know for certain what that means) with a pot? Any and all help would be greatly appreciated.

Finally, is it easy to drill through the wah enclosure with a regular home cordless drill? And can anyone recommend a particular pot to use?

Thanks in advance,

-Travis

[philbinator1]

maybe this will help a little, don't wanna delve too deep as i'm a noob myself 

http://www.electronics-radio.com/articles/basic_concepts/resistance/resistors_series_parallel.php

[MmmPedals]

Series means one after the other as opposed to paralell  which is one next to the other. so you are going to want the signal to go into the trim pot - out of the trim pot-then into the resistor. parallel would be the signal splitting into both the pot and resistor.
The signal goes into lug one of the resistor and out from the wiper (middle lug). `you can just lift one end of the resistor and solder it to the middle lug.

[SocraticTelecaster]

Probably a stupid question, but how do I tell which solder pad for the resistor is "lug one?" Thanks.

[MmmPedals]

WHOOPS. i meant lug one of the POT.

[flintstoned]

What I've done to my wahs is install a 100k pot for the vocal mod, removing the resistor altogether, but before you soder the pot, install it in the side of the pedal, tighten, then meter the ohms at 33k, 56k and 68k n mark those on the side of the pedal so you can tweak it any time you want. Just soder one wire to lugs 1 and 2 from where one end of resistor was and the other to lug 3

[T1bbles]

Finally, is it easy to drill through the wah enclosure with a regular home cordless drill? And can anyone recommend a particular pot to use?

Thanks in advance,

-Travis

Yes it is! What you'll need to do is get your hands on a couple of HSS (High Speed Steel) drill bits as trying to drill through metal with masonry or wood bits will blunt them very quickly. The reason you need a few bits is because when drilling though metal it's best to start with a small hole and enlargen it to whatever you might need it to be, it's just a safety thing, and helps to extend the life of your bits. So if your pot needs a hole of 7mm diameter, I would usually start with a 5mm bit, then enlargen it with a 7mm bit.

Also, it's important to use a slow rotation speed when drilling through metal to discourage the bit (and the pedal enclosure) from heating up. It helps to push rather hard on the first hole, but for enlargening the hole just let the drill do the work or you might crack the enclosure.

Thats what I know about drilling enclosures anyways. Hope it helps!

[SocraticTelecaster]

Okay - I think I almost have it. Clip one end of the resistor and lift. The clipped resistor gets soldered to the middle lug of the pot. I ignore one of the other two lugs on the pot and randomly pick one outer lug to attach to the hole in the PCB left vacant by the clipping of the resistor (am I right about the random thing - that it doesn't matter which lug the direct-to-PCB wire is attached to as long as it's an outer one?). Finally, can some please tell me - does it matter which of the two candidate holes in the PCB gets soldered in series with the resistor to the pot? Top one? Bottom one? Either one? Please help me, Obi Wan.

Thanks

[SocraticTelecaster]

Okay - I drew this up in Pages. Does this look correct? Thanks.

-Travis

[MmmPedals]

I would lift the resistor by heating the solder and carefully lift it with tweezers or pliers or lever it out with a screwdriver.
It will work no matter which one you wire it to but the pot will work in opposite directions. For normal wiring (left-down right-up) wire it to the "1" lug. if you get it backwards you could always flip it later.
YES it does matter which side of the resistor. here is the explanation of what is happening. When wiring in series it does not matter which comes first so i am going to assume you are putting the pot before the resistor but you can put it after it makes no difference. the signal as you have it now goes through a 33k resistor. you want to insert the pot before it gets there (or after like i said) so lift the side of the resistor which is receiving the signal. It should not be hard to follow the traces from the input wire until the resistor. Then you "take the signal" (i would solder a wire where you lifted the lead of the resistor) and put it into the pot (lug "1"). then the signal is taken from the wiper (middle lug) and continues to the resistor. This can be accomplished by soldering the lifted lead to the middle lug or using a wire to lengthen the lead if you want to mount the pot somewhere. Hope this makes sense.
If you would put the pot after the the resistor would go into lug 1 and out from the wiper to the rest of the circuit

[SocraticTelecaster]

Thanks MmmPedals:

Given that my board looks like this:


is this the correct way to wire the pot?


Thanks,

-Travis

[flintstoned]

Yeah that's better. Also get yourself a unibit for drilling, it will cover all the hole sizes you use for the jacks, pots, led holders and switches.

[SocraticTelecaster]

Maybe you guys could clear something up for me. I've posted the same question with the same wiring diagrams on The Wah Modding Thread @ the Ultimate-guitar.com forum site: http://www.ultimate-guitar.com/forum/showthread.php?t=476372

So far the replies I have received there have suggested that there is no difference between the two diagrams - both will work. One poster said "as stated above, it doesn't matter. But it might be good to know why that is. The pot is essentially an adjustable resistor, so you have 2 resistors in series, order is not important so both diagrams are exactly the same."

I'm a little confused here. Are they right? Is it really irrelevant where the wiper gets soldered?

If anyone can shed some light on this and help me to understand how these things work a little better, that would be great. I want to know both what the correct way to wire the pot is, and, why it is the correct way.

Thanks,

-Travis

[amptramp]

There is a good explanation of the effect of modifying everything on the standard wah pedal on this site:

http://www.geofex.com/Article_Folders/wahpedl/wahped.htm

The higher resistance will give you a higher peak in the underdamped lowpass response.  Good for some things, maybe not good for all, so a pot may be the best idea.