USB Flight Simulator Yoke Button Demultiplexer Issue

[iamdarkyoshi]

I got a flight yoke for free from my school because none of the buttons worked. Analog works fine, and if I remember correctly, I swapped this controller with one from another yoke to see if it was the yoke's wiring, and it was not. The issue (I THINK) lies in this controller:



It has three chips:

Decoder/Demultiplexer: 74HCT138D
 
Microcontroller: CY7C63001C-PXC (couldn't find a quick datasheet, here is a mouser link)
 
ADC (for analog inputs from yoke) TLC1543C

The issue is whenever I press a button, I get every fourth button pressed when I run a controller testing software.

For example:

I press button 1, buttons 5, 9, and 13 also appear pressed. Any button from this bank of four will activate the other three.
I press button 2, buttons 6, 8, and 14 also appear pressed. Any button from this bank of four will activate the other three.
I press button 3, buttons 7, 11, and 15 also appear pressed. Any button from this bank of four will activate the other three.
I press button 4, buttons 8, 12, and 16 also appear pressed. Any button from this bank of four will activate the other three.

Everything analog on this thing works flawlessly. What should I do to start troubleshooting? Where could the problem lie? For those wondering, I needed to put a scrap piece of metal in the socket for the micro as one pin was broken off, and I checked continuity on this pin, and it DOES check fine, so thats not the problem. I have already tried reflowing the demultiplexer with no change, and I have tried flexing the board, again, nothing.

[SeanB]

Have you checked for short circuits on the outputs of the ls138, or for a bad connection to pins 1-3 as these are the inputs. I guess the decoder is scanning the keyboard matrix and there are resistors dividing the scan down to button presses. Where are those resistors, there might be a shorted resistor or bad connection. Some photos of the complete board top and bottom would be good.

[wraper]

IMO 74HCT138D is faulty, not microcontroller.

I have already tried reflowing the demultiplexer with no change

[iamdarkyoshi]

IMO 74HCT138D is faulty, not microcontroller.

I have already tried reflowing the demultiplexer with no change

I never doubted the micro, and I wanted to try out my new SMD rework station "If its already fucked, no harm fucking it up more"

[sleemanj]

Put in a new 74HCT138D and see if it fixes it, not exactly hard to find or expensive :-)

[ajb]

One of the pins on the Cypress part is folded up on itself.  Maybe not the cause of the problem, but worth taking a look at.

[iamdarkyoshi]

One of the pins on the Cypress part is folded up on itself.  Maybe not the cause of the problem, but worth taking a look at.

This pin actually broke off, and so I fixed it by shoving a piece of flattened wire into the socket, and it makes contact with the broken pin stub on the micro. I already checked it with a multimeter, it is making a "reliable" connection.