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[Prime]

I have an A2500, it seems to work fine except for the mouse movements. The mouse buttons work fine, but the X, Y axis don't work at all. I read on NewTek's site that it could be a fuse, but I don't see a fuse (Small green soldered one that looks like a resistor.) I checked with an ohm meter from pins 5 and 9 all the way to the paula, which seems like a straight shot with no resistance. The only thing inline that I see is a ferrite bead. I guess the next thing I can check to see is, if the mouse port is receiving 5+. I already tried to replace the Paula and the CIA's.
Any Ideas?

Thanks,
Joe

[save2600]

Look REAL close at your motherboard, just to the left of the mouse port IIRC. Might be smack dab in the middle of the two also. There is indeed a TINY ceramic cased .5 amp fuse. Typical for these to blow (never plug joys/mice into an Amiga when it's on!). I have a few if you discover you need one. Try "jumping" the fuse first maybe and see if the optic sensors spring to life on your mouse...



Since this is a commonly failing part, I'd solder wires and a regular fuse holder to her - which is precisely what I did on mine. Haven't had to replace the fuse since, but will make it that much easier if/when it blows again.

[Zac67]

Forget PotX & PotY, they're the analogue inputs used for paddles and such. You need to check pin 7 for +5V. Check FB215 and especially F1 (possibly green, resistor-like) between keyboard and mouse port.

[Prime]

I still don't see the fuse, so here is a picture.
I am going to test for 5v.
If there is no 5v on pin 7, what then?




Joe

[Chain]

If nothing of above helps, locate U74 and replace it (74HCT157), preferably wit a socket

[JimS]

The fuse was added at Rev 6 motherboards. That looks like a 4.5. So, it could be a blown trace, if there's no 5v at the joystick port.

[save2600]

Ahhh yes... the good 'ol mobo revisions. Shoulda thought of that, shoulda thought... LOL! Indeed his mobo does not look like my 6.2.

Before changing out that U74 chip though, I'd test all of those diodes and tantalum caps running about the ports. Tantalums fail QUITE often (especially after 15-20 years) and when they short, chances are they would take out something else in line - like U74 if it's on that particular mobo. FYI: you MAY replace tantalums with electrolytics to be on the right side of preventative maintenance.

And a blown trace could have happened because of battery acid leakage you're thinking JimS? Or sloppy techs dropping their screwdrivers on the mobo too I guess. lol