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7800 controller resistor values


CMR

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How essential is it that these need to be 620 ohms?  Can they be a little over?  It looks like they're just holding pins 5 and 9 high until the switches pull them low.  Specifically I have some 680 ohm resistors.  Would these be OK or would having a slightly lower value (1 - 10 ohms) be OK?

 

This is the schematic I'm going by.  Thanks to whoever made it.

7800joystick.jpg

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On 3/26/2022 at 3:18 PM, CMR said:

How essential is it that these need to be 620 ohms?  Can they be a little over?  It looks like they're just holding pins 5 and 9 high until the switches pull them low

If you look closely you will see that they are connected to pin 8 (GND) and so would not be holding Pins 5 & 9 High. Are you certain that schematic is correct as I am not entirely sure what their purpose would be, I can only think they are providing some kind of noise immunity on the paddle inputs instead of them being left floating.

 

EDIT:

Remainder of post removed as I looking at things incorrectly.

 

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14 hours ago, Stephen Moss said:

If you look closely you will see that they are connected to pin 8 (GND) and so would not be holding Pins 5 & 9 High. Are you certain that schematic is correct as I am not entirely sure what their purpose would be, I can only think they are providing some kind of noise immunity on the paddle inputs instead of them being left floating.

 

In 7800 2-button mode, the console drives pin 6 high and these resistors pull pins 5 and 9 down unless the corresponding button is pressed.

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On 3/29/2022 at 12:20 AM, Pat Brady said:

In 7800 2-button mode, the console drives pin 6 high and these resistors pull pins 5 and 9 down unless the corresponding button is pressed.

My bad, my brain was operating on the inputs being active low when writing my previous reply as active low that is the Atari "Standard" for controller button inputs. 

As Pin 6 is being driven high it therefore does not really matter too much what the resistor value is (within reason) so with regard to the original question moving up or down to the next preferred value should be fine, although generally up would be better as it uses less current.  

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  • 3 weeks later...

I just finished modding a Competition Pro joystick by rotating the switches by 90 degrees so I get the buttons to the right side.

 

By using 10000 , 2200 and 1000 ohms in parallell I got 643 ohms that worked on my PAL unit.

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On 4/17/2022 at 1:39 AM, karri said:

I just finished modding a Competition Pro joystick by rotating the switches by 90 degrees so I get the buttons to the right side.

 

By using 10000 , 2200 and 1000 ohms in parallell I got 643 ohms that worked on my PAL unit.

 

I've seen that done with the 5200 version of the Competition Pro so the buttons are all on the left. Worked great when I played with it.

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