A1200 RMB constantly 'clicking'

I bought a new optical mouse from AmigaKit and tried it today in my A1200. All was fine for around 10 minutes or so but then it started to misbehave. First the mouse pointer refused to move after a reboot, I unplugged and replugged it back in and it seemed to work apart from the RMB.

I launched Cannon Fodder (first mouse based game I could think of where both buttons are required) and found once I got into the game my troops were constantly firing (as if the RMB was being clicked rapidly). I unplugged the mouse and the troops were still firing away.

I reverted back to my old ball mouse and this is doing the same. I removed everything superfluous from my machine then booted into Workbench from floppy with just power, video cable and mouse attached. Still, the RMB is not working.

I'm starting to suspect something got zapped or just coincidentally decided to die when I tried this new mouse. Paula perhaps??

You are not supposed to connect or disconnect anything with the power on. Something might have broke

[supaduper]

As said if you plugged in the mouse while `on` then there is a good chance of blowing something , its a known thing with Amiga`s.
here is a pic of the Mouse/Joystick circuit, could have damaged U34 also

[Daedalus]

Yes, there is always the risk of damaging something by disconnecting and reconnecting when the computer is turned on, and it's not unique to Amigas - any equipment can suffer the same unless it's been specifically designed to be hot-pluggable (e.g. PCMCIA or USB). In reality though, connecting single-point peripherals like mice or controllers is a very tiny risk - the main risk is connecting to things that has other connections, such as printers, modems or other computers.

If you're good with a multimeter you can check the circuit for pin 9 on the mouse port. The U34 IC isn't involved in the RMB so don't worry about that. Check the small capacitors on that line for a short (there are two) - if either of them is damaged and becomes short to ground, it will have the effect of constantly keeping the button clicked. It's unusual, but they do fail occasionally.

also, check for debris in the mouse socket, or perhaps something behind the mouse socket. The ground and RMB pins are next to each other and therefore could easily be shorted by a small bit of stray metal of some sort. Make sure there aren't any bent pins, and that the RF shielding isn't damaged and shorting to the board underneath the mouse socket. Check as well for any signs of capacitor leakage near the sockets and Paula. Generally capacitor leakage cuts circuits, but it can have other effects too.

Another possibility is a fault in Paula itself, but let's not worry about that until the other possibilities are eliminated.

[hooverphonique]

pullup resistor could be gone..

[Daedalus]

The pullup resistor is internal in Paula, so if that's the case it's Paula that's faulty unfortunately. But you may be able to get away with fitting a separate pull-up resistor if that's the only fault. It would rule out using analogue joysticks on that port, but that would be very unusual anyway.

No harm to try it though: connect a resistor between pins 7 and 9 of the mouse port and see if the firing stops. Ideally 4.7KOhm, but anything between 1K and 10K should do the trick. Be very careful of shorting pins 7 and 8 or you'll do more damage...

Thank you everyone for your replies. Oddly enough, I tried it again a couple of days later and it was working perfectly and has been ever since. As a precaution, I have stripped the whole thing down, re-soldered the ports and put it all back together. Perhaps something was short inside - who knows. I'll chalk it down as fixed for now but will be keeping an eye on it for a while.

[Codetsu]

i have same issue on my A1200
but it goes away when it warm up if you look portdiag (find Aminet)
you can see that there is some static on oneor both mouse direction bit
so U32 may get some damage. in side IC is some protection and if
they brake static can operate chip. it still work more or less