seqv4 problem

7 posts in this topic

hi people

im hoping someone can shine a light on this problem im having with a midibox seq4

it has the wilba control surface (its not the new seqv4+)

stepswitches 5 & 6 are not working (the guy who owns it tried to replace them...but he really did a grimm job soldering

i cant really see where the traces are going and to what ic these two switches connect (it can probably be fixed with a wire but i need to know to what ic and pin they are going)


any help is welcome,



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ok traced them down to U2...and that side is okay....but still can not find the fault.....are the switches connected to a groundplane or something ?

because he ripped off some solder pads


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Hi Vincent,

hope you are doing fine!

Have you checked the switches themselves? (Just use a multimeter and see if you get 0R resistance if the switch is depressed).
Some of the switches used in the Wilba V4 UI just failed after a while, my old V4 also suffers from this problem and has a lot of dead switches - i've currently retired it in the basement storage room! :)

As you asked, the step switches are "in between" an input channel, the step LEDs, a diode, and an output channel creating the matrix, so no direct connection to ground - see attached schem region that shows the step switches 5&6 (center bottom).

Many greets and good luck!



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hi Peter

thank you for helpling me (again you are my forum hero !!!)....but even with the schematic i can not find it.

hoping you can help me a little more....this is what ive cheked so far:

if i put my meter in beep mode and have one pin on the bottom left pin of Step switch 5 and the other pin on U2 pin 11....then i get a beep if i press the switch

the same goes for step switch 6 bottom left pin to U2 pin 12 ...also gives a beep.....

so this should be good right ?

ive also replaced the duo color leds and also both 1n4148 diodes...but it did not help

what other things can i check ?


with kind regards,



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Note that the Wilba board is wired in a way that the switch bodies carry some signals too. Think of the switch with two halves. 

A A'
B B'

When the switch is not pressed, A still connects to A' and B to B'. Think of it like a clipped resistor leg soldered between the two PCB pads. The idea/function is to act as a "bridge" to avoid lots of vias or a 4-layer board, as you can effectively jumper the signals over and under each other.

When you press the switch, then the switch acts as you think it should and connects parts A + B. Naturally all contacts are connected when the switch is depressed.


I would be tempted to load MB_NG and manually check the functions. E.g. you can read DIN events with set debug on (short the "cathode" part of the switch to 0V/ground) and simulate a matrix with set dout x y and try to gauge if the switch works that way.

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okay thank you


ive been testing the switches....they give a beep if i put my meter on them  A-A gives a beep and B-B gives a beep

and A-B gives a beep when switch is pressed......


one other thing ive noticed......with my own seqv4 the step led lites up green when i turn the encoder....with this board the led does not light up when i turn the encoder

so that is weird


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did some beeping again.....as this guy...himself replaced the menu switch....he probably damaged a trace .....

there was no connection between d21 and d35 .....

so its all working now


thanks guys !


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