Bending Yamaha PSR-6

I got my hand on Yamaha PSR-6 and of course I did bend it :)
here is the story, hope you can learn something.

after opening look for the big chips...

















here are the two main chips the XE323B0 is CPU and YM2413 is the FM sound chip.
and the PCB side looks like this(note:image flipped around for better viewing):

















there is nice information of YM2413
YM2413 FM Operator Type-LL (OPLL) Application Manual
and as far as i understand the CPU sends bits on eight data lines to FM chip and the sound's are made inside the FM chip...

after reading nice instructions on circuit-bent.net on bending PSS-270
I wanted to know more about the data flow between the CPU and FM chips. I installed LEDs that indicate if the pins are high of low, a kind of dataflow monitor.

some details:

wires attached to YM2413












wires coming out from little screw hole












transistor station














the leds and transistor station











And finally the schematic:

duplicate this 8 times.










here is a video of this thing running

next thing to do is the switches and the banana board.


here is my messy soldering but - everything is fine i checked whit multimeter - no short circuit's :)













and here is the 2mm mini-banana patch points (yellow -from CPU. green- to FM)


and here are switches for getting back to normal and for setting crazy settings


Quote, circuit-bent.net
"Each switch now controls the flow of data from the FM chip to the main chip. Turn the yamaha on and select a patch (let's pull up #89 "ghost"), I usually play some keys(don't know if you have to do this or not), then turn some switches off , now select a different patch, and turn the switches back on. Now try playing the new patch. If it went well some of the data from the all patch got held up, and then inserted into the new patch making a totally different sound. Sometimes leaving the connections off will change the sounds also. I've noticed them some of the bent up patches will only work when multiple keys are played. I've heard that this will effect the drums as well, but I haven't gotten it to do much with them as of yet"

after setting the bended tone - i messed around whit the banana patch -
it's sooo nice -
listen .mp3 sound samples

After making this I received some questions. Here are the questions and my answers:

Quote, mister.
"I have recently begun bending a Yamaha PSR-6. The only info I have found on bending for this model of keyboard was your's. I had a few questions if you don not mind. First I wanted to know how your particular approach came out (hoe pleased are you with the results). Second, I wanted some more info on your LED wiring. I have just begun learning more details on electronics and from what I saw on the forum I'm farely certain I know what you did, but more details would be nice. For example, what type of NPN did you use exactly? Also where the hell did you get those pin jacks? I have found some probes that look similar, but I don't know if there are any sockets for them. I have oredered RCA and will use those, but I like the pin jacks a lot and even if I don't use them on this project it would be cool for future work. Thank you for your time and much repect for your work from me. I hope you can afford the time to help me out. Any details you can give would kick ass."

Quote, sponge.
"hi there, i saw that you have successfully bend the yamaha psr-6. i picked one up the other day from a charity shop. im a little confused about what you were trying to do with it... sounded very cool though! would you be willing to tell me where the bends you found were, and what the LED / transistor circuits were for? i've found a couple of bends, but i've only bent one thing before, and that was a cheap effects pedal."


My answer:

Lets start whit the schematics and pics:

here are the main chips from the "solder side".
red dots are points D0 - D7 of the FM chip YM2413
and the blue dots are points D0 - D7 of the CPU chip XE323B0
yellow lines indicate where you need to cut the traces.

here is the YM2413 chip Pin Assignment:


here is the schematic:

you need to ad this circuit to all eight points (D0 to D0, D1 to D1 ...)

the transistors i used are C2389
- but you can use any general type NPN transistor. experiment whit the ones you have.


the bends i made are
1. 8 switches to control data flow
2. 8LEDs to monitor the data flow
3. data-patch bay to patch data

Haven't had much time to play whit my Yamaha but i must say that I'm pleased whit the results.

The method described in Kevin Rees site is good start.
here are some of my own that you can hear in the sample:
start whit sound 40, turn D0 off, change to sound 50 and turn the D0 on - start playing.
start whit sound 40, turn D7 off, change to sound 50 and turn the D7 on - start playing.
start whit sound 40, turn D0 off, change to sound 89 and turn the D0 on - start playing.

As you can now imagine there are MANY combinations .
after i have set a sound. i start patching - but that's not that easy - the monitor helps in this - but it crashes a lot - by trial and error you will learn :)

The D4 is used to trigger the sounds so if you have that turned off, nothing happens

The pin jacks i got from YEinternational but they only serve you in Finland, Russia and the Baltics. The pin jacks are made by Hirschmann. Maybe if you ask your local supplier if they have those 2mm pin jacks? they can arrange something.

About the LED data monitor.
Every time one of the points D0 -D7 goes high, LED D0-D7 goes on.
By looking the LED' s blink you can see the data flow and its easier to learn patching when you actually see whats going on in the inputs of the chip.

hope this helps

for more questions don't hesitate to post it here.

Daniel