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 Forum index » DIY Hardware and Software » Circuit Bending
Help! Missing Connections: Talk 'N Learn Phonics Keybaord
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Cyeos



Joined: Mar 17, 2010
Posts: 5
Location: Baltimore

PostPosted: Thu Mar 18, 2010 1:06 pm    Post subject: Help! Missing Connections: Talk 'N Learn Phonics Keybaord
Subject description: Need help figuring out where hookups go for speakers and battery on a PCB.
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Hello!

Purchased a "Talk 'N Learn Phonics Keyboard" toy several years back, but was disheartened when it arrived with the batteries and speaker lines disconnected from the main PCB. Trying again to get it going.

I took the time to draw out a quick schematic (see below) for the main PCB in an attempt to figure out where the missing connections go but still at a loss.

There is a c9013 NPN transistor I assume is used for amplification, but trying the speaker (+) to the open collector point X, and the (-) to ground only gave out a barely audible signal.

On my schematic, the gray area is the "blob" IC which I can't identify, the red blocks #s 1-11 are the ribbon cable hookups to the letters buttons, and the A-D blue circles are the hookups to the keyboard.

Green connections in X and Y are what I have open going to empty solder points.

Schematic

+6V AND speaker (+) connected to Y and speaker (-) connected to X seems to work, but it just doesn't seem right to me (and I'm worried about burning out the board.)

Any ideas anyone? Is it normal for speaker positive and power supply to share a connection and a speaker not go direct to ground?
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electri-fire



Joined: Jul 26, 2006
Posts: 535
Location: breda nl
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PostPosted: Thu Mar 18, 2010 3:29 pm    Post subject: Re: Help! Missing Connections: Talk 'N Learn Phonics Keybaord
Subject description: Need help figuring out where hookups go for speakers and battery on a PCB.
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Cyeos wrote:
Is it normal for speaker positive and power supply to share a connection and a speaker not go direct to ground?


I don't know your device, but yes, speakers are often connected to the +V.
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Cyeos



Joined: Mar 17, 2010
Posts: 5
Location: Baltimore

PostPosted: Thu Mar 18, 2010 3:36 pm    Post subject: Re: Help! Missing Connections: Talk 'N Learn Phonics Keybaord
Subject description: Need help figuring out where hookups go for speakers and battery on a PCB.
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electri-fire wrote:
Cyeos wrote:
Is it normal for speaker positive and power supply to share a connection and a speaker not go direct to ground?


I don't know your device, but yes, speakers are often connected to the +V.


Thanks for the response!

The device is this, if you're curious:
http://www.amazon.com/Scientific-LEARN-ELECTRONIC-PHONICS-KEYBOARD/dp/B000IHHNIC

Interesting, is it also normal then for the negative to connect to the collector of the NPN? How is the transistor functioning in that kind of setup?
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electri-fire



Joined: Jul 26, 2006
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PostPosted: Thu Mar 18, 2010 3:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hmm, the circuit seems ok to me. Maybe the transistor has passed away. Any NPN transitor should at least do something, so you might try repalce it.

Or try parallel R15 with a similar value for safety (or a pot) just try it briefly and you maybe won't ruin it. ( I didn't say that Wink ) , if that goes well you might try completely bypass it. Your Milage May Vary.
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electri-fire



Joined: Jul 26, 2006
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PostPosted: Thu Mar 18, 2010 3:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Cyeos wrote:
Interesting, is it also normal then for the negative to connect to the collector of the NPN? How is the transistor functioning in that kind of setup?


That's the emitter there that connects to ground isn't it? (sorry if I'm in error, I'm not that proficient in electronics)

But I think it should work like this. Audio out from the Blob circuit is from pin1 to base. With signal present the transistor would be conducting, so current would pass through the speaker thus should produce sound.

Ermm, come to think of that, maybe completel bypass of R15 would lead to exessive battery drain.
Edit: R15 has absolutely nothing to with it, best leave it alone, I was babbling.

Hey, try addding external audio to the base of the transistor see if that works. (maybe use a battery powered toy, and connect both grounds together )

Or connect pin1 to a toy with know to work speaker. Then you know weather the transistor is faulty or not.
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Cyeos



Joined: Mar 17, 2010
Posts: 5
Location: Baltimore

PostPosted: Thu Mar 18, 2010 4:44 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks guys!
I'm thinking maybe I'm not describing it right, so here's a new schematic showing how I've had X and Y wired up to get sound before.

Is this what you guys had in mind?

Schematic

I do think that's the collector at the top of the transistor, and the emitter going to ground, but I'm not positive : ) I looked up C9013 data sheets and associated that with the orientation of the transistor on the board...could be wrong or a different version.

I'll test when I get home, but I think my transistor is working (amplifying) fine, as the audio comes out pretty loud when hooked up like this and the built in volume control buttons work.

What I'm most worried about is not whether this is working to make sound, but whether it's doing it in a way it's not supposed to, and will burn out eventually. Ironic, I know, since once it's working as it was designed I'm going to BEND it.

Also, I'm used to speakers connecting to ground, so any other arrangement is new to me.

Thanks again.
-Ian
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electri-fire



Joined: Jul 26, 2006
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PostPosted: Thu Mar 18, 2010 6:40 pm    Post subject: Reply with quote  Mark this post and the followings unread

I gathered this was the circuit. You're totally safe and ok with this, it's supposed to be that way.

(and I'm sort of convinced the arrow like part of the tranny is called the emitter, but I'm too lazy to look it up now, so please correct me if needed)
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Cyeos



Joined: Mar 17, 2010
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Location: Baltimore

PostPosted: Thu Mar 18, 2010 8:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ya, you are right, the arrow is the emitter, the left is the base and the top is the collector.

I think I'm going to solder things like this, I'm glad it looks right to somebody.

I'm increasingly confident now that this is how it's supposed to be...the only other arrangement that I think should work....well...doesn't.
So, apparently, in this kind of circuit the transistor is "gating" the output connection to ground, if I'm using the term correctly.

I always assumed an amplified signal was coming OUT of an amp transistor, going through a speaker and then to ground. I guess you learn something new every day. Is there a particular name for a circuit where speaker connects direct to +V like this?

Already got an LED with resistor in parallel with the speaker that lights with the sound (pretty cool.) There's also a pin that if you ground it will make the chip regurgitate EVERY recorded voice line in a row, heh. Going to see if the usual 10K pot with the wiper connected to output will work for volume control on this.
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electri-fire



Joined: Jul 26, 2006
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PostPosted: Fri Mar 19, 2010 9:05 am    Post subject: Reply with quote  Mark this post and the followings unread

It's a bit of a perculiar circuit. The most obvious clock in/out's would be pin 2-3 , R1 being the most likely candidate to replace with a large pot for pitchbend. Then the two electrolytic capacitors are unusual, seemingly combining timing function and voltage stabilizing.

But then, pin3 must be the +V connection. So in this case replacing R1 would affect the powersupply of the entire circuit.

So just maybe you can get a better pitchbend by inserting a potmeter between pin1 and the capacitors. Maybe. I've tried bending a similar LOOKING device that too easily crashed when attempting to pitch it.

Pin 5-6 and 15-16-17 are intriguing. They're not used, still they're there? Some manufacturers do not implement features because it is cheaper to use a more sophisticated circuit than you need, just because it's readily available, instead of having to develope a more simple device.
When encountering unused pins there may be "easter eggs".

Ah, isn't it fun, a fresh toy to explore?
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Ciderfeks



Joined: Mar 23, 2010
Posts: 2
Location: Brighton UK

PostPosted: Tue Mar 23, 2010 10:06 am    Post subject: Reply with quote  Mark this post and the followings unread

I have the blue version with the serial DO-8006-1F on the main board. I've taken some pictures showing the power connections from the bat pack to the switch and main pcb. I've also shown you where the speaker joins the board too (assuming the layouts are the same!). Hope this helps! Let me know of any cool bends you find - I'll be getting into this one myself next week ; )


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Cyeos



Joined: Mar 17, 2010
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Location: Baltimore

PostPosted: Wed Mar 24, 2010 12:18 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks very much for taking the time to take and post photos!
I saw your YouTube comment as well.

You are right, though, my 8006 version has all the wires connected, but I appreciate it anyway.

8006 seems to be the most common, and I think the final letter on the serial number means which production run you have.

I'm currently happily hacking into a vintage Small Stone from Russia and have put the phonics toys aside, but I'll let you know what I end up with.
I've hooked up an LED that flashes with the sound and an 1/4" jack, but that's where I've left it.

Interestingly enough the 5085 version sounds slightly different.
I think it's an older version, but I like the "Car" sound better.

FYI: car sound with some effects going through a guitar amp sounded very cool.
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Ciderfeks



Joined: Mar 23, 2010
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PostPosted: Thu Mar 25, 2010 6:31 am    Post subject: Reply with quote  Mark this post and the followings unread

No problem - it seemed the decent thing to do given that I had the machine open in front of me when I read your post! - there was also another guy posting on Youtube with the same issue with his power leads so maybe it'll help him out. My phonics keyboard is an "English" version and has the words "zed" and "zedbra" clumsily recorded in place of "zee" and "zeebra" which is funny. I think there is a French version available too which might be fun. If I get any decent results out of the project I'll post the results.

Good luck with the Small Stone Smile
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