A quick stupid question! (soldering area) - Pitch Controls

[bentoutofshape]

After reading through the Reed Ghazala book that someone on here recommend to me.. I am not sure I am soldering in the right area :-/ The diagrams in the book show the compenents where I have been finding the bend points on the actual board side. Am I making a fluff up or what?

I guess whatever work though, eh?

(ADMIN EDIT - added 'Pitch controls' to the thread title)

[Dylan]

It doesn't matter what side you solder on. Whatever you can get to easier works. I like soldering to the actual solder joint side though, because then you don't have to add much more solder.

[Circuitbenders]

I have been finding the bend points on the actual board side.

You'll have to be more specific there. The two sides are usually referred to as the solder side and the component side. As Dylan says, its a lot easier to work on the solder side, but its not practical on every occasion.

I wouldn't trust any diagram 100%, especially on a toy like a speak&spell or similar. These things went through so many board revisions in their production lives that even after about 10 years i still come across versions i've never before, with components in completely different positions.

[bentoutofshape]

Alright. I see. I was also wondering, and I do not want to clutter your board up with basic questions .. Are these going to be good to experiment with:

http://www.rapidonline.com/sku/Electronic-Components/Capacitors/Radial-Electrolytic/105-deg-C-General-purpose-radial-electrolytic-capacitors/180812/11-3726

What I mean is I am not going to keep getting painful shocks and they are going to make noticeable changes to what I am working on (s&s/casio pt series) ? feel free to make suggestions.. I would just go ahead and get them and others but I have to pay per order and I want to be sure as I will buy in bulk.

[Circuitbenders]

well, my advice would be to not bother with caps unless you really need them to build a specific circuit. Poking around with caps probably isn't going to provide anything spectacular, although those definately wouldn't shock you. You'd need something rated a LOT higher than that

[bentoutofshape]

Excellent! I was wondering if I should bother with those at the moment. One more tedious question and I am going to scurry back to the workshop.. I have located a place where I can change pitch, I have put in a 100k pot and I am getting all happy about being able to change the pitch.. However, I am wanting the pitch to dip down even lower and go up higher. I need to fit a resistor either side of the pot, right? I would just go ahead and try but, being my first bend things are a little ragged and I don't want to ruin what I have already done   

[Circuitbenders]

sometimes if you pull out the pitch resistor and replace it with a pot, you might have to stick a resistor in series to stop the resistance dropping too low. On a lot of toys the lower the resistance the higher the pitch, but if you take it too high it might crash the whole thing. Sticking a resistor in series sets the minimum resistance, and therefore sets the highest pitch possible.

It will also take the lowest pitch a little lower as the maximum resistance will now be the maximum resistance of the pot PLUS the series resistor to stop it crashing. You probably won't be able to get the pitch any higher but you can probably get it lower with a bigger pot. i usually start with a 470k and work from there.

[bentoutofshape]

Are you saying to take out an existing resistor (the pitch resistor) and put a pot in its place?

[Circuitbenders]

yes, i thought thats what you'd already done. If you leave the pitch resistor in there and just bridge it with a pot then the maximum resistance will only ever be as high as the resistor thats already there.

take the pitch resistor out and replace it with the pot.

[bentoutofshape]

Oh right. I think I have missed the idea or something. I have found a point on the board that when it makes body contact it reduces in pitch.. I take it I should be looking to find the pitch resistor(s). Are there any techniques or tell tell clues?

[Circuitbenders]

Right, if whatever you're working on actually has a pitch resistor it will be around where the pitch changes when you touch it. If you have a definate body contact point then its going to be a resistor coming from there. Try licking or dampening the end of your finger and using it to bridge a likely looking resistor. If the pitch goes up wildly then you've probably found the right one. If it crashes then try again with less moisture on your finger.

If you desolder that resistor and replace it with a pot then you'll have a pitch knob in theory. This will only work on cheap stuff though. Its not going to work on something that actually has steady pitch like a Yamaha Keyboard, or probably the Casio PT you mentioned.

What is it that you're actually working on?

[bentoutofshape]

Yep, it goes up a lot when I bridge it.
I managed to go through a collection of my sister's things and find and then start working on a Casio PT10. I guess I will take the resistor out and try a pot in its place. You said that this might not work though, what other options do I have?

[Circuitbenders]

if the pitch goes up a lot when you bridge a certain resistor just try taking that resistor out and replacing it with a pot.

The problem manufacturers sometimes have with using a resistor to set the clock speed like this is that the pitch will tend to drift as the batteries run down, and its not going to be that accurate in the first place. This doesn't really matter on crappy toy keyboards, but on more expensive things that actually make some passing acquaintance with tuning you'll usually find a timing crystal, coil or ceramic resonator to set an accurate clock.
I don't know if this is the case with the PT10 but you'll need a new clock oscillator to change the pitch on these machines. Theres some info on the main site on using an LTC1799 chip to do this http://www.circuitbenders.co.uk/tutorials/LTCinstallation1.html

The actual chips are also available on the shop page.