DIY Pedal Attempt

[whitebison66]

It's embarrassing that this thread is over a year old!

But I am starting on it again, and I of course have questions.

I think the most important is how to 'move' the on/off function. The original effect has a push-pull pot, and I need to know how I can alter the wiring to include a footswitch instead.

Ideally, I'd like to leave the original pot in place, but I don't know if that's possible because of the on/off function. I know I tried to take it off and that didn't work; keeping 6 solder points fluid was more than I could manage.

 

[NQbass7]

As long as you have an effect in/effect out solder point, you can always just use those and a 3pdt footswitch like this: http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b/

And then just leave the push/pull in the "on" position.

 

[whitebison66]

NQBass7, that link is GREAT. It's very helpful for someone like me who is an utter noob at this kind of thing.

Okay, an update.

I had a newer version of the Tone-X, and I actually had two of them. So I decided one of them could be sacrificed, and I carefully removed the push-pull pot by undoing tabs and cutting away the other parts, and removing the soldered portions, until I managed to get it all removed from the board.

I hope to be able to figure out where to wire the new potentiometer in.

The casing of the pot (actually the switch portion) is labeled 250k, so a standard 250k pot would work, right?

This is starting to look like I can do it, so please keep your fingers crossed for me, and thanks to everyone for their help!

 

[mayfly]

It should work, but watch your taper.  Do you know if the current pot is log or linear taper?  Depending on the filter circuit, it could be either.  If you want to know for sure, hook up an ohm meter to the original pot and see how the resistance varies with position. 

 

[whitebison66]

The original pot is in about 12 pieces  :dontknow:

I've been doing some reading about it, and since the pot is stationary, some people say the taper is not as critical, though I am sure it affects the overall sound somehow. I just don't know how!

 

[mayfly]

The original pot is in about 12 pieces  :dontknow:

I've been doing some reading about it, and since the pot is stationary, some people say the taper is not as critical, though I am sure it affects the overall sound somehow. I just don't know how!

Got a photo of it?  particularly the circular resistive element.

 

[whitebison66]

I hope this is what you mean, because it's the only thing I could find that wasn't too small or broken to be photographed  :sad1:

 

[Jumble Jumble]

You could still test it with probes. Put one at the end, and gradually move the other around the resistive strip. You should be able to work out the taper from that.

 

[whitebison66]

What do I set the multimeter on?

How will I know which taper it is?

What difference will the taper make in the overall sound?

Sorry for all the ???s, I'm just flying blind here.

 

[Cagey]

Most pots are linear. That is, at 25% rotation you have 25% of the total resistance between one side and the wiper (with the inverse being 75%), at 50% of the rotation you have 50% of the resistance, and so on. But, since human ears have a logarithmic response curve to them, pots that are used for "volume" or "gain" have a curve to their response. In modern pots, it's not so much a curve as it is a stilted pair of linear ramps, but it's close enough for rock 'n' roll. The resistance vs. rotation is called the "taper".

So, in testing, if you see 50% of the total resistance at the half-way point, you have a linear taper pot. If it's less than that, it's probably a log or "audio" taper. Keep in mind that pots are sloppy things - the tolerance range is wide, often as much as 20%. So, if it's a 500K pot, the total resistance will be anywhere between 400K and 600K. It's usually not that critical, so nobody bitches.

 

[mayfly]

That looks like a linear taper to me. If it were log, the outside track would be ramp shaped. Well, a circular ramp is you get me. 

 

[whitebison66]

This is where I'm at.

Found a photo online showing the 250k stamp. And a better photo of the circuit board.

I've also been working out what goes where and to which.

The input and output operate from the middle lug, so I will assume the footswitch goes there.

As for the AC power, red is positive, black is negative, yes?

I think I'll try a standard 250k volume pot wired normally and see what I get.

 

[whitebison66]

I got about 3 hours' sleep last night, and I know I should back away from the computer and take a nap, but I think I maybe got it...

Using the images from the link on the 2nd page, here's a mockup of how I think it works.

 

[whitebison66]

And the answer is... no.

On the good side, I do get a signal with the pedal off. So at least that means the switch is working.

On the bad side, when you switch the effect on, there's no sound, no LED.

I need a different barrel jack anyway, and a new 250k pot wouldn't hurt either.

But at least it looks like a pedal.

So I got that going for me.

 

[whitebison66]

Would this wiring make the difference?

 

[NQbass7]

Would this wiring make the difference?

As far as I can tell, the only difference between this one and the one I posted earlier is that the effect input isn't grounded in the "off" position. Grounding the input to the effect board is useful because it helps to remove "pops" that occur when you turn the effect on, which happen when the input from the guitar connects to the input of the board and suddenly changes the (previously floating) input with essentially an impulse input.

If you get signal with the pedal off, that means at least part of your wiring is okay. Check to make sure you have good connections and no cold solder joints (https://www.google.com/search?q=cold+solder+joints&tbm=isch), specifically on the middle row for the LED. As far as no sound from the effect, my suspicion would be something on the effect board, not switch wiring - but you can always try disconnecting effect in/effect out from the board and connect them together to check your switch wiring. Once you have that working, you can look more closely at the board to figure out if something's wrong there, or if you have a cold solder joint somewhere.

Also, standard advice from the BYOC forums: post large, detailed, non-blurry pictures of the board, switch, and any other solder connections for help in debugging  (Personally I'd recommend using imgur.com and then posting links here, so as to not use up Warmoth server space for the pics.)

 

[whitebison66]

Thank you for the reply! I've started backtracking (and modifying my ambitions). I think I need to leave the pot on, because wiring it as originally intended (i.e. aping an onboard installation where the mono jack becomes the input and the stereo the output and using a 9v battery) it still doesn't work.

Neither, upon testing, did the 'blue board' version on page 1. Luckily, I had a 2nd 'green' one, and it works fine when wired 'traditionally.'

So now I've just got to work out the switch and AC, which hopefully will work as indicated.

I'll have to leave the push/pull in the 'up' position, but I think some hefty rubber washers under the knob will prevent it shutting off. 

As always, thanks for the help!

 

[Cagey]

You might want to invest in a set of alligator clip test leads, such as these...

You can use them to temporarily connect things up and see how they work without having to mess with stripping and soldering leads and cursing the daylight when they don't.

You can get them at Radio Shack if you must, but even places like Amazon have them available for $3 to $5 a set. Very handy little buggers.

 

[whitebison66]

I think that's a very good idea, Cagey. We don't have RS here, but I am sure I can get them in the electronics district. It would probably save time, effort, burn cream, hypertension meds, etc.

I've got the switch working, but not the LED or AC jack. I've gone back to 9v battery power, but can't get the LED working. I followed the schematic above, but I am not seeing anything.

But the effect works, which is a step forward.  :blob7:

 

[Cagey]

Be aware that you may end up with some noise in the circuit while you're testing due to long leads and lack of shielding, but at least you'll know if it's gonna work.

You can also use them to play substitution games with tone caps, resistors, pots, etc. to find which values work best.

Edit: When LEDs don't work, more often than not it's a polarity issue. They're diodes, after all, and only work when forward biased. Yet another reason to have some test leads so you can easily swap how something polarity-concious is connected.