BEND: Casio PT-30

[playthatbeat]

I had a PT-30 when i was a brat.. Monophonic, boom-chik-a-boom portable crapmaster from the 80's.. See it's manual here and read the excellent story here It was pretty shite now i think about it - monophonic, and thos nasty party rhythms and autochords. But, it DID take a dump and come out with UNIQUE noises if You giggled the batteries in & out.. Oh man.. YES it did. Haven't managed to make this one do that yet sadly..

I decided to Bend it. Well, i decided to mod it for trigger input (see my VL-1 post) and one thing led to another.. I didn't tap into the cpu, i scratched into the tracks coming from the button contacts instead, cos it looked less likely to fail, but same principal as the VL-1 tap - get an external trigger to close the contacts on the OKP button..

See firstly my main jpg for what i think i found on the board, plus a closeup of the CPU on the far side of the board hiding behind the display - cos i know You will be Curious if You have read this far.. one side of the cpu is for noises and triggers, mostly leading to the ribbon cable to the componant board, one side drives the display, and one scans the keyboards and buttons , while the last side seems to be for the Tape interface and extra memory.. Also: what i found on the ribbon cable that connects the 2 main boards that is fun to bend with.. This ribbon cable is badly attached usually, and breaks easily.. so be prepared to rescue this.. did i mention the display is not to be jerked about? well it isn't. So if you are doing the s-trig input, make it quick, tap into one of the ONE KEY PLAY buttons and gtfo. I have driven the memory play with an external LFO perfectly, it's capable of clocking to quite a high rate too, and very tightly.. so, clocking the main voice is Go.

I loaded the space meant for the useless tape interface with switches, a mini pot for input dampening to the s-trigger board, and a minijack in for the s-trig on the edge and corner to the right. Then put 2 pots either side of the speaker (after some grinding on the plastic with the dremel).. was going to lose the speaker, and fill the space with stuff to play with, but had a change of heart.. glad i left it in, now it's fully 'fireside' compatible for my next jam session in the woods at night.. er..

There are some really easy bends to be had on the percussion noises.. adding in caps, shorting caps out etc. the transistor noise can be made well swishy, and the filtering is easy to open up or 'punch' using triggers meant for something else in the rhythm.. Shades of the soundmaster SD88 here, you'll like it.. except, the kick is shite.. But, a bend makes the kick distort, which is nice. I of COARSE popped some of the transistors trying to make them squeal, the usual C1815 trannys are all over this machine, so no bother there.. Bound to happen sooner or later..

There are some other bends in there too - i have only pointed a good places you are sure to get things that make you smile and won't kill the machine.. have a look at the other 2 jpgs - they show the wire job when it was finished.. you can see i added some power-seeping taps not marked in the first jpg. - down in the bottom right corner. They do the usual howling crap in 2 stages - they go to a pot via a 3 way switch, 2 extremes and a not-connected.. depending on power source, these sound radically badass, especially when you drop the tuning to grind levels - it's best done only if you intend not using an external power source, so batteries only for that one i think.

[playthatbeat]

So, let's hear this baby..

First up on the attached file - some nice chaos drones, done by wiggling the battery - then some more noodles with wiggles, then some bends and rhythms, then some autochords and autobass, and then, well, You'll see that the PT30 has a moroder bassline in there!

I worked the file a little - editing it down from 15 mins to this 11.. I reckon this would make a good seed for a new noise track - just sayin'.. As it is, it's defo candidate for Xmas number 1 in this state, or to be dropped at the end of a set by someone like ******, or phil collins... Fu*k yeah transistor noise.

Still didn't make it do that wavetable videogame noise i remember it doing when i was a nipper.. do want to hear that again - it was the motivation for fleabaying it in the first place TBH..

[playthatbeat]

http://www.youtube.com/watch?v=c9gaYjlek38

[playthatbeat]

So, if You are tempted to have a go a ruining Your PT30, but don't want to bother with complicated crap - focus in on the ribbon connector you can see at the top right of the main board.. The most right-hand pin is GROUND, we will call this pin 1, and number the pins from there thru' 16. You can see from the first .jpg i kind of identified what most of the pins do by probing with the scope, so it should be easy to predict what will happen when You start to short them to one another..

Here's what worked for me as mutes, interesting & less interesting:

3 --> 5,6,7,9,11
5 --> 6,7,10,11
6 --> 10,11,15,16
7 --> 9,10,11,15
8 --> 9,10,15
9 --> 11
11 --> 14,15
12 --> 15
13 --> 15

If You intend hooking up all of these, You can save alot of cable by only patching once from the ribbon connector to the switches, then patching further from the switches instead of running duplicate cables from the ribbon connector - this keeps the clutter down and means you should be able to get the covers back on afterwards! You can expect some serious log jam if you use more then one bend at a time, which is nice, but You can always diode the taps if You want it more predictable.. i suppose..

[digitalallstars]

Most excellent, you have my deepest repects
well done, that pt-30 was the reason we all became synth junkies,

manys the afternoon was whiled away, playing it after school
ah pt-30 , dangermouse & buttery toast.

auto chords, fdim7th, cmin4th, I mean,
it still knows more about how to put notes together than most of us


and heres the mt68 the one kilian had- bent
found the yesterday co-incidently,
then found a heap of casio bum chigga bum vsts

bum ti ti ti ti ti ti buddaly diddaly buddaly !

ah ah ah ah !

http://www.youtube.com/watch?v=PuRhP...eature=related

the same one going through an ems synthi
http://www.youtube.com/watch?v=hmCRa...layer_embedded

[playthatbeat]

ah the MT-68.. it's chassis appeared in several units i think.. they hit on a winning design there and kept re-packaging it.. In fact, they were very good at that.. the PT-30 has a lot in common with the VL-1.. They really were just pulling a 'pong on a chip' on these things.. the CPU in the PT-30 is made by NEC, and it does almost everything.. Timing, main voice synthasis, keyboard scanning, button scanning, display etc. all you had to do was make some noise generators to be triggered by it's rhythm sequencer (or not as in some machines..), and put it in a case with controls to make a product.. Much talk about 'easter eggs' that were just non-implemented functions on the chip.. like hidden voices and rhythms..

lol casio.. everybody's first knee-tremble...

[playthatbeat]

dangorange PM'd me about his beloved pt-30 - he had been dicked by the ribbon cable connector, which is now borked after some fiddling.. he has started on re-attaching the rogue lines, but i thought i'd sahre how i did it..

i sliced thru' the connection plastic in the ribbon connector either side of the broken line, then i could lift away the line on it's on - abotu an inch or so was free, then i removed 1/2 of the length, and peeled back some plastic, and soldered on a run of thin flexible wire (actually a line from an IDE connector cable) i then attached tape over and under the join, attaching to the remaining bits of the ribbon cable. this meant the new join has the structural support of the remaining ribbon, but also moves with it when it flexes. I then tacked on the other end of my new wire to a point on the board - NOT the original place the line used go to - that i cleaned up of old solder.

I ended up having to patch 3 of the f*ckers, and on the 3rd run i wrapped the whole last inch of the ribbon in tape - using a knife to pass the tape under the ribbon.

those joins are old and dry, and the cable is brittle.. so dont try to re-attach the same to same in any way, you will just cause trouble.

speaking of trouble, You should see dan's display it's full of garbage, and some of his keys are not happy.. also, depending on what is playing fromt he sequencer, oddness happens - like missing sounds or notes. this ALL smacks of 'crossed wires' or something shorting out on the way to and from the CPU. remember, that little NEC thing does everything - scaning the controls included.

During my test bending phaze, i found it easy to fill the display with crap and lock up the machine, but i do remember from having one as a kid that ropey power sources can also make that happen..

[dangorange]

First post and it might as well be here. Big thanks for the help so far from playthatbeat. This PT-30 was the very first keyboard given to me (must of been around 7 yr old) and sort of catapulted me into the world of infatuation of old analog synths and the like.

For years the keyboard's been dead with a garbled display. After finally having enough experience fixing small things, I had a go at is and got it back to working order. As celebration I decided to turn into my first circuit bend, and research led me to this very thread.

So far I've managed to break it several times, turn the display into garbage, and then get it back up and running. Like mentioned, the ribbon cable is proving to be the biggest pain, but so far this method laid out, pulling back the plastic etc. seems to be the way to go.

Hopefully I'll have something to show for all this soon, but wanted to say hey in the meantime.

thanks! Dan

[dangorange]

i sliced thru' the connection plastic in the ribbon connector either side of the broken line, then i could lift away the line on it's on - abotu an inch or so was free, then i removed 1/2 of the length, and peeled back some plastic, and soldered on a run of thin flexible wire (actually a line from an IDE connector cable) i then attached tape over and under the join, attaching to the remaining bits of the ribbon cable.

Curious, did you cut the entire ribbon cable and then reattach all 16 points? Or just pull out enough to access that length for the broken connections. This CPU error I keep getting is troublesome. It comes and goes, and currently is on the fritz again. Thinking about redoing the whole ribbon cable at this point...

[playthatbeat]

i just did it to the lines that had broken.. it might be an idea to replace the whole thing if you intend opening it alot, the metal in the ribbon is so very brittle

i bet that CPU error is down to a short, if You had fried the chip itself then it would just be locked.. the fact it comes & goes points to some oddness somewhere.

Also: if you do all your bending tests on batteries, you can't do any real damage, even if you go for really random bends (because you can!!!) there really isn;t the current there to fry anything.

I think You should look at a good cleanup inside, and follow each line on the ribbon cable from it's origin on the CPU/Control board to the destination on the audio board, see if there is any wierdness along the way.

[dangorange]

Thanks,

I actually cleared the error message, it comes and goes, probably due to a short as you mentioned. Also, I've only used battery power, the ac plug is long gone and never bothered to replace, my dad swiped it from it 30 years ago to fix something else!

Right now I have a new problem and have it shelved until I can figure it out. Basically I have no sound either through the speakers or headphone jack. Everything seems to be working in terms of the lcd recognizing different selections etc. But no sound whatsoever, not when I turn it on, hit a key, try any bends. Very weird.

This has happened and it's always been a bad solder joint but I can't get anything.... Any thoughts are greatly appreciated!

[playthatbeat]

Mm.. not even a click on the outputs? When you plug it in or out?

I'd start with the obvious and trace back from the output socket, using something plugged in to start.. You'd be amazed at how simple it MIGHT be..

Just test for continuity, cos' a totally dead output - no clicks no fu*k-all sounds like something physical.

If it IS clicking (etc.) on power cycling, then thats something.. try the old 'wet finger' on things on the way to the outputs, again, listening for buzzing or clicks you may cause.. work your way back..

Then the last resort is to look up everything chippy, get the docs and see if the pins are behaving like they should be - if not, trace back from iffey pin (etc.) and/or repalce chip.. especially if you suspect it could be used as an audio aplifier or switcher..

Then, transistors - they DO pop. You CAN kill one by bending or looking for bends, or just bieng careless and shunting power somewhere silly.. Luckily, all the transistors You can proably replace with something vaguely the same. Even a mobile phone ringing next to it, or you wearing nylon socks can KILL something filled with oldschool transistors.

I feel for You.. But keep at it.. if It looks bad then shelve it for a year or so.. DO NOT smash it more in a temper.

[dangorange]

Yeah, it's totally odd, not a peep whatsoever from anywhere. No clicks or anything when start up, touching anywhere etc. Looks all healthy and the lcd registers all selections made.

Just no sound through speaker or headphone jack