Joypad dpad right direction fails sometimes on the CD32

[wairnair]

About half the time I power on the CD32 the joypad dpad doesn't work in the right direction. Left/up/down and all other buttons work.
Solution can be:
* plugging in a joystick in the other port - this rarely solves it
* plugging the joypad out/in solves it most of the time
* if all else fails, then plug in the joystick in the joypad's port, then plug the joypad back in. This always solves the problem.

Restarting the system, or even completely powering off/on mostly doesn't help.
The joypad is a competition pro.
I remember to have seen the joystick refuse to go right once, so the culprit is most likely the machine (and not the joypad/joystick).
Cables are all good and once it works, it works till the next time it's powered on.

I've replaced the 74LS166 shift register on the mainboard because it didn't go in any direction at all when I got the machine.
It's denoted U34 on the schematics, https://www.amigawiki.org/dnl/schematics/CD32_R3.pdf

Anyone experienced similar? Can someone reason this?

[Daedalus]

If you plug in a joystick in that same port, does the joystick work in all directions? Have a look at the pull-up resistors for the direction inputs, make sure they're ok. Measure the inputs into the '166 chip with the joypad connected, see if the signal (pin 4 IIRC) is high when right is not pressed and low when it is pressed. It could be as simple as a damaged connector too - are any pins pushed back or bent in the port?

[wairnair]

Originally Posted by Daedalus

If you plug in a joystick in that same port, does the joystick work in all directions?

Yes, joystick works in all directions in the same port. In fact it "cures" the port, because plugging in the joypad after the joystick always makes it work.
So I suspect the electronics as opposed to something mechanical.

Originally Posted by Daedalus

Have a look at the pull-up resistors for the direction inputs, make sure they're ok. Measure the inputs into the '166 chip with the joypad connected, see if the signal (pin 4 IIRC) is high when right is not pressed and low when it is pressed.

I'll check this one, thanks.

Originally Posted by Daedalus

It could be as simple as a damaged connector too - are any pins pushed back or bent in the port?

The port is mechanically OK, I've checked all pins.

[Daedalus]

That's very strange, since electrically, a joystick is identical to the D-pad on a CD32 controller - there's nothing involved other than a switch that connects the pin to ground in both cases. So I can't see how the joystick can fix the port unless it's some sort of mechanical issue that the joystick connector puts right. Maybe a poor solder joint to the mainboard from the port?

[robinsonb5]

Are you absolutely sure there isn't a break in the controller's cable, or a dodgy connection at the plug? All the things that fix your issue have one thing in common - physically disturbing the cable and connector.

[wairnair]

Originally Posted by robinsonb5

Are you absolutely sure there isn't a break in the controller's cable, or a dodgy connection at the plug? All the things that fix your issue have one thing in common - physically disturbing the cable and connector.

Yeah good point, I'll double check the cable/port.

[wairnair]

Turned it on, dpad right direction didn't work. Moved the plug pretty hard up/down and guess what, that's all it needed. It may need resoldering or changing the connector. (It's probably not the controller's cable/plug because it does the same thing with an extension cable.)

Dumb me overthinking this.
Thanks guys, case closed I guess.