last button board not working

e8abac78cdf65c56

hey. the bigger of the button boards is not working, but only in sense of buttons, the leds are fine. only a few buttons are working - rest not. so a shematic would be good too debug this scan matrix… thx

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More info required. What buttons work?

If the switch behavior is erratic, then the issue lies either with the cabling, or the input or sink side of the matrix.

Disconnect and test cables and rebuild if necessary
If a column of four switches doesn’t work correctly, the issue is with the 74HC165 chips or 10k resistors
If a row of switches doesn’t work correctly, the issue is with the 74HC595 chip

e8abac78cdf65c56

about more info:

is it right that the LEDs are 100% isolated from the Button-Shematic? something like this: http://www.ucapps.de/mbhp/mbhp_dio_matrix_8x16buttons.pdf and this http://www.ucapps.de/mbhp/mbhp_dio_matrix.pdf ?

@ WIRE: if the serial chain itself or the Cables of it would be dead - the Axis-PCB Buttons would not work - i guess - but they work.

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Thanks for the video. Looks otherwise quite good so far!

LEDs are completely independent from the buttons. That’s more or less a button matrix as you’ve linked. Sinks along rows (595 chip), inputs along columns (extra column goes a bit differently).

It seems like buttons in a column are lighting up multiple rows? I would thus suspect the 165 chips (IC1/2).

Check as well that you soldered all 10k pull-up resistors and diodes have the correct orientation.

Did you install BAT54S diodes? You could try bridging the pads on D87 (SOT23 package) and see if that helps, but only after verifying ICs.

A good picture of the back of the board would be useful to spot if anything looks strange, though you can focus mostly on the ICs.

e8abac78cdf65c56

No i did not soldered the the BAT54S.
I also replaced all 595 and 165 on the last 2 Button-Boards.
see Video:

It has something to do with serial chain on the board which is before the last board - maybe with the Cable-Socket. or a trace is broken anywhere.
The Cables itself are ok.
So i need some assistance about the serial chain interconnection (which is the last IC in chain?)
and
how is the Pinout of J89 socket

i already have desoldered the 4 Buttons that are at the top of the J89 Header, but i cant see the pins (they are under the Metal-Plate…. the last thing i seed is to dremel out a centimeter of the metal plate to see/ work on the J89 Solderpoints.

e8abac78cdf65c56

Is “R4” really existent? ( i dont find it)
I found R3, it is 10K, and when i measure PIN 10 of IC1 to +5V, then i got 11k > seems ok.

By measure PIN 10 of IC2 to +5V - then i got 3,5MOHM (normally i should measure here 10K, but R4 is not existent - i guess) > maybe that dont hurt anynthing…

I measured the whole Serial Chain, incl all Clock and Supply pins off the 595 and 165 over 2 Boards > and it should work! the serial chain is intact!, Cable, Socket, Chips, PCB > OK!

I bridged D87 > so we have a GROUND there, but that dont help (done on the Last Board, which is not working)

hmmm.

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Sure, R4 is above J89B (output header). Hard to tell from your picture, but did you solder a capacitor in there?

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Check also R4 on the previous board, also seems to be the same colour as a capacitor.

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R4 is 10k, hidden at the opposite end of the board, right up against J89B

e8abac78cdf65c56

YES, R4 was indeed a 100nF (on booth boards the last and the one before)
I replaced it on booth and now its working > THX!!!!

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A picture is worth 10 000 ohms!