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Amiga computer related discussion => Amiga Hardware Issues and discussion => Topic started by: BosonMichael on January 22, 2010, 05:07:03 AM
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I've got a problem with my Amiga 500. The Joystick 1 port seems to be having problems. Here's what happens:
Joystick:
- button works
- hold stick L, cursor moves up 1 pixel; release stick, cursor moves back down
- hold stick R, nothing happens
- hold stick U, nothing happens
- hold stick D, cursor moves right 1 pixel; release stick, cursor moves back left
Mouse:
- connecting it causes Workbench bar to flicker between "Workbench release/free memory" and "Workbench Disk Special" drop-down menus.
Keyboard works fine.
I swapped the CIA 8520 chips, but the problem does not change. Any ideas?
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I've got a problem with my Amiga 500.
I swapped the CIA 8520 chips, but the problem does not change. Any ideas?
Despite some strange popular belief, the CIAs have no involvement with joystick/mouse movement. In the A500, the 4 movement lines are read by U4 (Denise). Reseating or replacing this socketed device may solve the problem for you.
The 8 to 4 line multiplexing (to read the four lines from the joystick movement and 4 lines from mouse movement) is switched by U15, a 74HC/LS157. Replacing this might solve the problems as it may have been damaged. I think it's soldered in as opposed to being socketed. The multiplexer is under control of a system clock which is generated by U2 (Gary), so reseating this device may fix it as well.
With a bit of luck it might just be yet another problem caused by IC sockets.
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I had similar issues with an old 500 mobo many many moons ago. I had to steal the 74x157 from another board to fix the issue.
Come to think of it, there was also a component blown on the board which fed power to the socket. I would have to find the board to know for sure, but I do remember that the two were related. The previous owner had somehow shorted out the port and it blew the component (I think it was a resister) and the multiplexor chip.
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Thanks to both of you. I'll reseat Gary and Denise and see if that helps. If it's a soldering issue, I might as well bury it or sell it for parts, because I cause more problems than I fix with solder. :( I wouldn't even know where to take it to get it fixed.
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I wouldn't even know where to take it to get it fixed.
That all depends on where you live!
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That all depends on where you live!
Aha! Thanks for that, fixed my profile. I'm near Nashville.
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Hmm. I was just about to post that nothing happened after reseating Gary and Denise (and Paula for good measure)... but it looks like the behavior HAS slightly modified:
hold stick L, nothing happens
hold stick R, nothing happens
hold stick U, cursor moves down 1 pixel; release stick, cursor moves back up
hold stick D, cursor moves right 1 pixel; release stick, cursor moves back left
Wondering if I should replace Gary and Denise... obviously something happened...
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You can try this cable as it mimics the mouse and joystick of Amiga through PC's parallel port but it doesn't use the +5V (pin 7). If mouse/joystick works, then you have some blown fuse (+5V). If it doesn't, you have some chips to replace. I have been using an Amiga 2000 w/blown fuse w/o any problems.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=320478538308
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Thanks for all your help on this issue. I finally learned how to solder and tried out my new skills on replacing U15. However, in trying to remove U15 (man, that was difficult!), I damaged the component next to it - if I remember correctly, it's C15. Anyone have any idea what this component's specifications are?