Getting into a VTech Letter Fun PC

Bogus Noise · August 04, 2010, 05:23:55 PM

Trying to get to the main circuit board on one of these:

The keyboard section just has keyboard stuff, the screen section has the interesting stuff, but I can't get to it! There's two little red plugs/caps, one either side of the speaker/hinge area. I've got those out by drilling a hole through the centre and prising them out with a handy implement (a thin allen key, in my case).

So now I can slightly see inside the screen area, but there still seems to be a bunch of screws holding the screen area together, but I think their heads are under the plastic screen graphic/protector.

Have seen a couple of bent ones around, anyone here successfully gotten into the thing without damaging the original look of the toy?

Bogus Noise · August 04, 2010, 10:56:52 PM

Ok... I made it inside. The extra screws were indeed under the screen protector. It's got a lot of glue on it so would take ages to gradually prise it off with a flat screwdriver or knife, not to mention you run the risk of damaging the protector in the process.

However you can use a knife to lift up the edge of a corner, and prise up a little bit, then spray some isopropyl alcohol underneath - the glue will dissolve pretty quickly and you can lift it off much more easily. A few spray/lift cycles and it'll be off safely in no time!

Dylan · August 05, 2010, 04:23:02 AM

I have one of these, once you crack it (which you have) they're pure sweet glitchiness. I found some cool glitches and a hold/drone bend. man, I sure do need to start bending again.

Bogus Noise · August 05, 2010, 05:06:22 AM

Hehehe, yeah I've been at it now, some good stuff in there! Got the hold point and looks like pretty much anything to anything on the big chip causes glitches, figure that's the data and the actual CPU business is in the blob. Bit more testing to do yet but looks to be a fun one.

Dylan · August 06, 2010, 05:40:48 PM

if you find anything else, let me know! I'd love to add more to this.

Bogus Noise · May 11, 2011, 05:27:39 PM

Mine's finally finished and recorded!

Didn't find much else really. There's LOADS of glitch points, so I put in a rotary switch to choose between 5 base points, giving 25 glitches from the push buttons instead of 5.
Also a couple of distortion type things from connections coming from the speaker. Not particularly aggressive, but it definitely opens up the sound when you've got hold turned on, some wicked waveforms for throwing into the sampler right there.

Ah yeah - the hold button got expanded with a 555 to act as a rudimentary timestretch.

Circuit Bent VTech Letter Fun PC

jossCardiff · May 11, 2011, 05:56:31 PM

love the speech bits around 2.45!

Circuitbenders · May 11, 2011, 06:31:53 PM

That gargling muffled underwater voice is very familiar. From the sound of it thats exactly the same speech synth chip as is the TI computer fun, which was released in 1988!

http://www.datamath.org/Speech/ComputerFun_UK.htm

The timestretching type effects around 2:30 onwards are brilliant.

Bogus Noise · May 12, 2011, 05:33:25 AM

Thanks, glad you both like it

Just had a listen to the TI Computer Fun recording on your main site, not sure it's identical but sounds a bit similar yeah!

I've found I get very similar glitches out of a few of the speaking VTechs - the blue-backed Alphabet Desk and the Little Smart Answering Machine for two. Also did a Grandstand IQ Builders Talking Computer which had similar stuff going on.

(Can hear that one at http://youtu.be/C_sEQHNFDsU)

I'm thinking the basic concept for making 'standard coil-clocked speaking toy with separate sample ROM chip' is fairly similar all round, so it glitches out in a similar way. Well, there's likely to be a few approaches, but one of them was used quite often in the 80s and 90s.

Though curiosity got the better of me and I had to open it up to check, but both of the ICs are VTech branded, and can't find any info on them.

Circuitbenders · May 12, 2011, 11:28:09 AM

Quote from: Bogus Noise on May 12, 2011, 05:33:25 AM
Though curiosity got the better of me and I had to open it up to check, but both of the ICs are VTech branded, and can't find any info on them.

Hmmm, i can't imagine VTech developed their own speech chips though. Its probably much like you see the same black blob chipset with those four drum sounds in about a million different small keyboards and drum toys.
Why develop your own system when theres something already available that works, that you can licence.

Dylan · May 12, 2011, 01:49:56 PM

That thing is AWESOME! I'll have to open mine back up this weekend and look for some more stuff in there.