e-licktronic Forum

The sequencer appears to be functioning correctly, but every step of every pattern triggers a cowbell lol. I can program the cowbell as normal, the LED's light up and go out like nothing is wrong, but every step goes bongggg regardless.

Has my machine been posessed by Christopher Walken? Or is it a more standard problem? I did have the board bare on a bench for several months so it's possible something got physically broken during that time, but I don't know where to look/don't know what part of the board could cause this

Thanks in advance!

the cpu generates individual triggers (like gates) for each instrument as well as the "accent" and shifts them out serially onto shift registers (IC5, IC9)
then, the accent trigger goes into a circuit which turns it into a voltage level dependant on the accent knob, this is then labbeled as "TRIG" in the schematic and goes to each instrument together with the instrument's individual trigger
the "TRIG" (which carries the accent level) is then multiplied together with the individual trigger
if the instrument is not triggered you get TRIG*0 which equals 0 and thus - nothing
in your case i suspect the individual trigger fails to go low, or is shorted or semi-shorted (pulled) high
check pin15 of IC9 (that's the cowbell individual trigger, labelled CB)
it should normally stay low, i think, or just compare it to one of the others - pin1 is the cymbal trigger

if the voltage there is sane, the problem could be further in the path
after the shift register, CB goes into the cowbell section, entering at one side of R4*
Q1*, Q5*, and the surrounding resistors there are a somewhat common chunk of circuit which (i think) does the multiplication of the TRIG and individual instrument trigger signals, you can see that structure in pretty much every other instrument

Now that's a detailed and intelligent answer Antto. Where did you acquire this knowledge? Ever since I've been building Yocto's and Nava's this year I've been trying to learn everything I can about synthesized musical instruments, and I have probably learned the most by reading through all the posts on this website from super smart people like yourself. Are you self taught or did you go to school for electronics? Anyway, great answer!

i pretty much didn't learn anything in school, so i guess i'm more "self-taught"
i've gone from interest in music creation (on computer) to interest in sound synthesis and processing (in parallel i learned mIRC scripts for silly reasons), then SynthEdit, then i learned C++ in order to make custom SynthEdit modules
from there i was on the hunt for the 303 sound, and tried to approximate it, things were very blurry and unserious at first, till i received lots of help from other people
at some point then i actually managed to obtain a 2nd hand x0xb0x which pretty much resurected my blurry attempt at 303 approximation and kicked it in a new direction
i learned a whole lot of things during that time, while trying to understand how the 303 works (both the synthesis side, the sequencer, the idea of the whole machine)
i struggled with the schematic, i couldn't understand what's going on at all
anyways, i completed that adventure at some point and moved on
now since 3 years i was hired at a job where i code for 8bit embedded stuff, and i had collegues doing ASM coding and the actual electronics design and troubleshooting - it's here where i managed to finally understand some of the basic things in circuits like voltage/current/resistance which i failed previously
and during these years i've also been going back to the x0xb0x and looking again at the schematic and trying to help others debug problems with their units (i even managed to spot a bunch of issues surprisingly accurate)

the yocto has some similarities with the x0xb0x digital section (shift registers, rotary encoders and selectors)
the 808 itself afaik is closely related to the 303 (the same roland guy involved in both of them)
so now with the stuff i've learned, schematics don't appear so alien to me anymore
well, i still struggle with nonlinear components like transistors

i even created a few schematic designs myself recently at work, when the electronics guy was away

i think none of this would've happened if i had to learn it in school, because in school usually you "have to learn something or else you don't pass" while i find it hard to learn something without this serving some useful purpose afterwards

Thank you for your response. I'm now 57 and I would say that every skill I use in my daily life, whether it's hobby or other has been self taught too. I'm glad to see you're using your brain for something good instead of letting it go to waste. Keep it up...

Danny