A500 mouse/joystick problem

[BosonMichael]

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?

[Castellen]

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.

[LoadWB]

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.

[BosonMichael]

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.

[tone007]

I wouldn't even know where to take it to get it fixed.

That all depends on where you live!

[BosonMichael]

That all depends on where you live!

Aha! Thanks for that, fixed my profile. I'm near Nashville.

[BosonMichael]

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...

[amigaksi]

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

[BosonMichael]

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?