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Joystick stick won't function, fire buttons OK

Submitted by arukum17 on July 31, 2008 - 7:25am. Hardware Repair Help

I am using a vintage TG Products Joystick on an Apple ][. 1978 Rev 1 motherboard with 16 PIN DIP gameport I/O.
Both fire buttons work but the joystick stick movement does not produce any movement on the screen (not even a jerk)
Tested with Pacman, Centipede and Defender.

When I opened the joystick unit the internals seem minty clean. Just two pushbuttons and two potentiometers with mechanical trim adjustments.
Output is a 16 pin DIP plug with all legs OK. I have a pin-out for the gameport I/O.

Have you come across a similar situation
How should I proceed to further diagnose and if possible resolve this problem?
Where can I find a joystick test program? (I don't have the ability to download disk images at the moment)
Anything I can check with a multimeter?

Thanks for the help.

Arun

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Armed with my wonderful auto-

Submitted by arukum17 on July 31, 2008 - 12:08pm.

Armed with my wonderful auto-ranging multimeter I will be checking various capacitors on the motherboard and resistance from the joystick. I understand there are 4 .022 microfarad capacitors on the motherboard which are used for joystick functionality. Also will check the pins coming out from the joystick to see if any resistance variation is detected.

I am hell bent on getting this to work ;-)

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I am also going to use the fo

Submitted by arukum17 on July 31, 2008 - 2:11pm.

I am also going to use the following program to display stick values:

20 PRINT "X= "; PDL(0); TAB(15); "Y= ";PDL(1); TAB(30);
30 IF PEEK(49249)>127 THEN PRINT " B0";
40 IF PEEK(49250)>127 THEN PRINT " B1";
50 PRINT: GOTO 20

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Yippee! Works fine now. Op

Submitted by arukum17 on July 31, 2008 - 10:27pm.

Yippee! Works fine now.

Opened the joystick. Check resistance with ohmeter. Cleaned with contact cleaner.
Tested pinouts for continuity. Tested 4x 0.022 uF capacitors on motherboard OK. Resistors OK. Ran the diagnostic program above, got values from 0 to 255 for X and Y.

Booted up Centipede and to my glee the joystick started working again.

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Contact cleaner seems to be t

Submitted by resman on August 1, 2008 - 2:15pm.

Contact cleaner seems to be the holy grail to getting these old joysticks working. I've used it to get the buttons working on a few too. Enjoy!

Dave...

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