On 8/18/2011 8:20 PM, Bill Garber wrote:
"Michael J. Mahon"<mjmahon@aol.com> wrote in message1583854341335345069.915437mjmahon-aol.com@news.giganews.com">news:1583854341335345069.915437mjmahon-aol.com@news.giganews.com...> "Bill Garber"<willy46pa@comcast.net> wrote:>> "Michael J. Mahon"<mjmahon@aol.com> wrote in message >> 333722398335260254.430904mjmahon-aol.com@news.giganews.com">news:333722398335260254.430904mjmahon-aol.com@news.giganews.com...>>> Antoine Vignau<antoine.vignau@laposte.net> wrote:>>>> On 15 ao�t, 02:31, Eric Rucker<bhtoo...@gmail.com> wrote:>>>>> So, I know that there were both PC and Apple II versions of the CH Mach III. >>>>> >>>>> And, I know that PC joysticks are (typically) 100k ohm, whereas Apple II >>>>> joysticks are 150k ohm. However, I've seen that some PC joysticks DO use 150k ohm pots. >>>>> >>>>> So, what pots did the Mach III use, in both Apple and PC versions?>>>> >>>> I have one but I don't feel confident in opening it to give the answer >>>> to you. >>>> I've been using it for 25 years now and I want it to continue! >>>> >>>> Sorry, >>>> Antoine>>> >>> You can measure the maximum resistance without opening it by connecting an >>> ohmmeter to the appropriate pins of the connector. (After all, this is how >>> the computer measures the resistance. ;-)>> >> Michael, >> >> This won't tell you what hardware is inside. Extra circuitry would be used to obtain >> the proper range of resistance required by the inputs. You could actually use quite >> larger POTs and add capacitance to bring the range down. :)> > The internal circuitry doesn't matter, as long as it doesn't include a > supplementary capacitor. Only the resistance at the terminals is important > in the absence of an internal capacitor.Agreed, but, the question remains, "So, what pots did the Mach III use, in both Apple and PC versions?". Since they are assumed to work, the supplementals can be figured mathmatically.
True. But since a supplementary capacitor (switched, in this case) can be used to make a smaller resistance have the same time constant as a larger resistance (with only the Apple's capacitor), and since cost is always an objective, the pots will be 100k--"native" to the PC. In PC mode the capacitor is switched out, and in Apple II mode a small capacitor is switched in. The value of the joystick capacitor is approximately half the value of the Apple's built-in timing capacitor. One is needed for each pot. -michael NadaNet 3.1 for Apple II parallel computing! Home page: http://home.comcast.net/~mjmahon/ "The wastebasket is our most important design tool--and it's seriously underused."