Jump to content
telengard

Replacement pots for Apple brand joysticks

Recommended Posts

I 3 of these and all of them don't register in certain directions (usually goes out to about 212 of the full 255 when testing).  Taking the joysticks apart, the total resistance of the non-working pots are less than the working ones (~133 ohms for working, ~122 not working, some even lower like 95).  My CH Premium IIs do not have this issue at all once calibrated. 

 

Certain games seem to be tolerant of this, others like my favorite Loderunner, are not.

 

Are these pots available somewhere?  They'd need to have the same resistance value, shaft diameter/threading, etc.  Or would a larger resistance value work, like a 150?

 

Also, these joysticks are NOT fun to disassemble, tons of little mechanical parts, and a plastic nut shaft.  :(

Edited by telengard

Share this post


Link to post
Share on other sites
On 10/10/2021 at 2:16 PM, telengard said:

I 3 of these and all of them don't register in certain directions (usually goes out to about 212 of the full 255 when testing).  Taking the joysticks apart, the total resistance of the non-working pots are less than the working ones (~133 ohms for working, ~122 not working, some even lower like 95).  My CH Premium IIs do not have this issue at all once calibrated. 

 

Certain games seem to be tolerant of this, others like my favorite Loderunner, are not.

 

Are these pots available somewhere?  They'd need to have the same resistance value, shaft diameter/threading, etc.  Or would a larger resistance value work, like a 150?

 

Also, these joysticks are NOT fun to disassemble, tons of little mechanical parts, and a plastic nut shaft.  :(

The Apple ][ JoySticks are 150K Ohms, as I recall...  Which is an uncommon value, but it probably has something to do with the Charging Circuit that is used..

 

MarkO

  • Like 1

Share this post


Link to post
Share on other sites

Thanks for the info everyone.  I have other joysticks to use (CH, Suncom, Kraft) but I liked how these look.  Too bad they don't work so well, all 3 are now on a shelf until I can find some 150K pots.

Share this post


Link to post
Share on other sites
19 hours ago, telengard said:

Thanks for the info everyone.  I have other joysticks to use (CH, Suncom, Kraft) but I liked how these look.  Too bad they don't work so well, all 3 are now on a shelf until I can find some 150K pots.

You probably won't find any 150K pots.  Those are unicorns.

 

You'll have better luck maybe finding 100K pots or even 10K pots.

They will work if you add compensation capacitors in parallel with the pot.

 

The 150K pot forms an R-C "network" with some 0.022 uF capacitors on the motherboard to make some timed-pulses out of the 556 timer that the pot is connected to.

So if you use some (quite common) 10K pots, you'll get the equivalent performance with a 0.3 uF cap in parallel with the pot.  Or substitute any other value according to the formula example:

 

10kΩ * (x + 0.022μF) = 150kΩ * 0.022μF

x + 0.022μF  = (150kΩ * 0.022μF) / 10kΩ

x  = (150kΩ * 0.022μF) / 10kΩ – 0.022μF

 x = 0.308μF  

  • Like 1

Share this post


Link to post
Share on other sites
On 11/24/2021 at 7:03 AM, Baldrick said:

You probably won't find any 150K pots.  Those are unicorns.

 

You'll have better luck maybe finding 100K pots or even 10K pots.

They will work if you add compensation capacitors in parallel with the pot.

 

The 150K pot forms an R-C "network" with some 0.022 uF capacitors on the motherboard to make some timed-pulses out of the 556 timer that the pot is connected to.

So if you use some (quite common) 10K pots, you'll get the equivalent performance with a 0.3 uF cap in parallel with the pot.  Or substitute any other value according to the formula example:

 

10kΩ * (x + 0.022μF) = 150kΩ * 0.022μF

x + 0.022μF  = (150kΩ * 0.022μF) / 10kΩ

x  = (150kΩ * 0.022μF) / 10kΩ – 0.022μF

 x = 0.308μF  

Thanks for the Formulas...  I know when adapting JoySticks from One computer System to another, "adjustments" might need to be made..

 

MarkO

Share this post


Link to post
Share on other sites

They'd be compatible if they were 3/4 turn pots like most of the ones used in joysticks. 

Sizing and fitting become obvious issues.  But it's nice to see that they are available in one form or another.

For a while they could not be found.

 

If your joysticks pots are lower in resistance and they are reliably precise (that is, they have smooth transitions and don't change in total value) you can easily correct for the lower resistance with the capacitor formula above.

 

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

  • Recently Browsing   0 members

    No registered users viewing this page.

×
×
  • Create New...