Calling all Monkey Ball joystick experts!!!

[ReidPar]

I've been slowly restoring an original US Monkey Ball, and I've hit a snag with the joystick... I could use some help, as I'm a full-fledged amateur.

TL;DR the original joystick is drifting during gameplay and drifts different amounts as you play. I've tried calibrating it several times in the test menu to no avail.

I'm gonna try to give as much context as I can, in case it helps.

• When I first purchased it, I believe there was a short shaft Sanwa joystick installed with a poorly 3D printed banana. I didn't test much, or recalibrate, but I recall there being a little drift. This joystick was hooked up directly to the JVS IO board via the 26-pin CN7. I removed this joystick.
• The previous owner happened to have an original joystick, banana, and amp board. However, the harness had several wires cut, and the connector was wired wrong.
• I installed the OG joystick and the amp, which was easy because all those wires were untouched. But I had to redo the 26-pin connector. I followed the general Naomi wiring diagram here. Pins 1 and 2 for 5v each. Pins 3 and 9 for 1P V/H VOL. Pins 23 and 24 for ground. I used a pin crimper with Dupont 2.54 mm pins, but for some reason the pins are loose and come out easily. I was able to insert the connector without the pins coming out by doing so gently.
• I fixed the cut wires using WAGOs and made sure the amp board was getting both 5v wires, the grounds and the V/H VOL.
• I recalibrated the joystick in the test menu. I rotated pretty hard and let go a few times. When I let go the values are jittering a little. I tried a few more times with no improvement.
• When I first start playing, the monkey is perfectly still. But, after playing for a few mintues, or when a hard direction change happens, it starts to drift. The amount of drift varies, sometimes a lot, sometimes a little. It can also be horizontal or vertical.

I'm at a loss as to what could be wrong. It doesn't seem like the pots are bad, but maybe?? Is it the amp board? Is my 26-pin connector wiring bad? Any thoughts are greatly appreciated!

 

[nnap]

I would take the stick apart and clean all the dirt, then regrease with lithium grease. Before you do, male a lot of pictures so you know where everything goes. Especially the orientation of the pots. The metal pieces that hold the pots have 2 screws. Do not tighten those. Just screw them in until they are snug. Otherwise the stick will bind.
To me your issue sounds like the stick is slow to return to center or does not return to center at all. Cleaning an regreasing should help.

 

[ReidPar]

Thanks for the tip, I'll give it a shot.

I did apply a little grease before, without dissembling. The stick spring is good and it snaps back to center very well. So I'm not sure if that's the issue.

Could it be a ground or voltage issue?

 

[nem]

Pots and the cylinders the pots attach to would be my guess.

I recently changed the pots on my Monkey Ball stick because of drifting. However, even after changing the pots the joystick still drifted. After pulling apart the stick I noticed the cylinders had worn insides. One had even cracked. There's two pairs of cylinders, you can just swap the pots to the other pair.

 

[ReidPar]

Update: I dissembled the joystick and cleaned and re-lubed. The pots definitely felt kinda weird/grindy. All the other parts seemed fine. So my current guess is the pots!

Nem, do you know where to find the right pots?

 

[nem]

I had an original pair of unused Tocos RA25Y 20FB5K pots here that I switched over to. Tocos pots can be hard to find, but you're looking for

Right angle panel mount, with ear-lug terminals
Wirewound element
25mm diameter
20mm FMS (From Mounting Surface) shaft length
Flatted shaft end style
Linear resistance taper
5k ohm resistance

Also, here's a pic of the cylinders I mentioned before:



You can see how one of them has cracked. The shaft doesn't grip the sides and it is loose. That means when you return the joystick to neutral, the pot can still be at an angle, causing drifting.

There are four of these cylinders inside each stick. I suggest swapping the "fresh" pair that are not attached to the pots with the ones that are.

 

[ReidPar]

Thanks nem!

When I dissembled, these pieces seemed to be okay. But I’ll take another look when I open up again. I only noticed 2 of these however, not 4. 2 plus the plastic drum with 2 sides. Is there anywhere you’ve seen to purchase replacements?

Wanted to double check: it was mentioned to use lithium grease but I used silicone grease. Was that a bad idea?

 

[nem]

I use silicone grease too.

That's interesting that there were only two. I wonder why I have extras then?

You can order replacement parts from Sanwa, but you have to ask for them by email.

Part list can be found in this older Sanwa catalog, page 10:

https://rs2006.co.jp/e/sanwaseimitsu/Sanwa2020.pdf

 

[ReidPar]

First up, thanks again Nem. You're the man!

I ordered some replcement pots, but I mistakenly got the 25mm length shaft... whoops.

But, I opened up the joystick again and this time looked carefully at the cylinders you mentioned. I noticed one was barely moving when I moved the joystick! So there is defintely an issue. I'll report back with results once I get the right pots.