SEQ with Wilba PCB assembly issues - buttons not working :(

7 posts in this topic


I'm currently in the process of building the awesome Midibox SEQ using Wilba's front panel PCB from SmashTV's shop. I am using an STM32F core board. I have soldered the following on the front panel PCB:

- All diodes

- J1 connector

- All 5 pin resistor networks

- All IC sockets

- All pushbuttons

- Capacitors


I have not soldered ANY of the following:

- Resistors

- Rotary encoders

- LEDs

- Anything else I am missing?


I have two LCD modules connected to my core board (and they work fine), and the front panel PCB (to J8/9). Pressing any of the buttons does not do anything. 

Things I have checked:

- All diodes are in the right orientation

- All ICs are in their sockets in the right orientation (U1-U6 are the 165, U7/8 are 595)

- I can see a clock signal on J1 SC pin. I can see VCC and GND.


One important mistake that I made: I initially soldered the J1 connector in the wrong orientation (or the flat cable I used is different than the one that's on the photo instructions thread). This resulted in U1 overheating and may have ruined it or anything else. After discovering this awful mistake I used wire patch cables to connect the core module and the PCB so I am fairly certain they are properly connected now (I can see a clock signal on SC, and measure ~5v between VS and VD). 


Does anyone have an idea of what can be wrong? Here are some theories that I have but not sure if they make sense:

- I ruined some or all the ICs - thankfully they are socketed so I will just order a bunch of new ones and try that next week.

- I ruined something else - I doubt that because capacitors, switches and diodes are pretty resilient and I can't see reversed connector being an issue

- This thing does not work without the LED resistors (I doubt, but maybe I'm wrong? I couldn't find a schema of the board online).


I have access to a 2 channel scope so I can look at signals if someone has an idea of what would be worth checking.


Many thanks!

Edited by keves

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Something else to check is the orientation of resistor networks, they have a dot which must align with the PCB legend.

To test if the chip survived, you could try to swap some around and see if you can get a bit of functionality.

Depending on the buttons you ordered, it is still possible to misalign these by 90 degrees.

Edited by latigid on

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Thanks for the reply :)

I also checked the resistor networks, they are properly placed. I used the buttons SmashTV sends in his parts kit, and they cannot be misaligned. I ordered new chips so I will just try that next week when they arrive.

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Had the same problem once - with the 180° rotated cable. I doubt, you ruined your shift registers, mine got very hot and I did not realize it for a few minutes (drinking that coffee was more important! ;-)).

I therefore suspect sth else, but I might be wrong, ofc :-).


Make sure, that Serial IN and Serial OUT (SI/SO) lines are not accidentally swapped. This could still happen, if the cable is built wrong. You can test to swap these lines (nothing bad can happen).

A good test is to use a continuity tester / ohm meter to map the silkscreen printouts of J8/J9 with J1 on the SEQ CS.


A few other tips:

Check for voltages across the CS board. Every IC must be powered with 5V across its supply pins.

Enable the SEQ Button test mode in the MIOS Terminal.

Insert a few resistors and LEDs (no real need to solder), just add 9 220R Resistors at the center of the board around the center encoder slot and add just one LED above the first GP button - it should light up after booting.

Attach your scope with the probe to the serial lines and (and probe gnd to gnd). You should see high-speed pulsed signals on J2 of the CS PCB (it is a serial extension of the inputs from J1 to attach other hardware, like the TPD board).


Many greets and good luck!



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Thank you for the detailed reply!

I am embarrassed to say it was SO/SI - can't believe I didn't double check that one! Seems to work now :D :D :D

The ICs indeed seem to have survived even though the did overheat like you mentioned. Oh well, now I'll have a few more of them :)

Thanks again, this made my day!!!

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Congrats and enjoy that SEQ V4 - the best hardware sequencer on this planet (R) ;-)

Many greets,



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Super looking forward to have it fully working!


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