Callesw
Offline

Hey guys!

I'm new to this forum, and super new to this whole world of modding stuff (and new to electronics in general). My only achievment so far
has been to add a pitch bend to a very simple toy synth. I had no problem in finding the pitch resistor on that one, by licking my finger
and poking around a little bit.

I am now trying to do the same thing on another, a little bit more advanced synth, but with no luck!
I'm using the same method of finding it, and I've been going over the board a lot of times. The synth is called "Music time keyboard 310".
Below you can see a photo of the circuit board. I'll gladly take more photos if needed!

I'm thinking that maybe some of you guys see something that I'm missing, or maybe point me in another direction:)
Cheers!

Knife Crimes
Offline

Not all sound toys have a 'pitch resistor'. Sad but true.

The Holtek HT3494 chip in the photo is the 'brain' of that keyboard. I found the datasheet here: http://www.datasheetspdf.com/pdf/760735/Holtek/HT3494/1 It uses a crystal oscillator (or what looks like a ceramic resonator, marked X1 in the photo) as its clock. You may have luck effecting the pitch by interfering with X1 or the pins it is connected to.

Keep modding but! Break some shit! Circuit bending is about exploration as much as anything.

Knife Crimes
Offline

Callesw
Offline

Hey!

Thanks a lot for the pointers and info!
Just experimenting with it seems like a fun and learning way of approaching it!
I'll try to use this project in that way and see what happens. If it breaks it breaks:)

Cheers!

PansySharp
Offline

Hi...i don't the more expensive vtechs have those adjustable coils? I doubt this one has though, i'd say theres a resistor and you've missed it somehow. Sometimes v-techs have smaller boards coming off the main board that have a black blob chip and the pitch resistor on them.

order pcb

Last edited by PansySharp (Feb 3, 2020 10:03 pm)

Duck
Offline
London, UK

Hi - the datasheet for that IC is online here;

https://www.datasheetarchive.com/pdf/do … erm=HT3494

it says it is clocked by a crystal oscillator in the chip, so (I think) there won't be a pitch bend in the way you're expecting.

Maybe you can work something else by starving it of voltage or something.

Duck
Offline
London, UK

oh. sorry, somehow missed the other post saying the same thing!

Duck
Offline
London, UK

maybe you might have luck inserting another/different clock across X1/X2 too?

a la:

http://getlofi.com/gameboy-dmg-01-pitch-modification/

(or maybe you'll have luck making magic smoke!)