mb808 din issue

MIDIbox SEQ
1

hey everyone

i seem to have a few bugs in my sequencer section of my mb808

it all lights up and i can play with patterns however

some of my button leds seem not to work for the menu 1 - 4 and loop rwd fwd stop and play but the buttons work

i can see them working on my lcd, well except for menu 1, menu 2, menu 3. i dont think they are working. pattern leds and buttons are all fine as are mute, pattern, song and edit

anyway the main issue im debugging is my instrument encoder not working. the other encoder works but not this one and im not sure how to debug these digital sections. i can trace the encoder’s ground triggers when i turn the encoder, (ie the 5v dropping to ground in a short trigger each time i click it round). i can see these on pins 6 and 7 of the assoicated shift register. i cannot however seem to track the output of the register to the core. even on the working encoder this is the case. using the ucapps schematics for the din and core modules ive check that RC and SC connectivity is ok. so im a little stumped

so i would love some advice on how to check through this.

i asked on the mb808 forum but patronage  seems low over there at the moment

2

I don’t know anything specific about MB-SEQ or MB-808, but did you try swapping the shift register chips and/or the encoders with known good ones?  (It sounds like you tested the encoder thoroughly, but swapping might be sure.)  That would help narrow down if this is a problem with the encoder, the shift register, the PCB/soldering, or the PIC.

Are other inputs on the same shift register chip working?

You could try to clock the serial register manually if you don’t have a logic analyzer (like most of us), but that might be going a bit crazy and I probably wouldn’t bother unless I got really desperate.

Good luck!

3

hey a reply!, thanks fussylizard

there has been no responce on any forum about this till now

some of the pins are working on this register

from what i can tell 1 of the 8 inputs on this one

the other registers function ok

i did try swapping the IC around but no effect

i guess i could try desolder the encoder but it seems to be ok since the output it looks the same on the scope as the working one.