Amiga 4000 mouse port - no up or down movement

[majestyx]

I swear, it seems like if it wasn't for bad luck I'd have no luck at all. No sooner do I finally get my A4000D/040 into good modern shape, lo and behold, the mouse port decides to stop moving the mouse up and down. It will move left and right, the buttons work too, but no vertical movement.

As a test, I played Speedball 2 in 2-player mode. The joystick port (port 2) works fine - all movements and button works fine. When I plug the joystick into the mouse port (port 1), it moves side to side and the button works, but when I push down, it moves down then quickly reverses and moves up instead. If I push up then down a few times, it will finally move down, but when I let go, it almost always moves up again.

I've tested it with 3 different mice and they all act the same way so it must be the port. Any advice on what's happening and how to fix it?

[cpiac64]

trace interrupted or 74hct166 dead

[Daedalus]

Possibly also a short on pin 1 due to corrosion or some sort of residue, or a failure of the relevant pull-up resistor (R981). If pin 1 is constantly active (low), the mouse will never move up or down, but joysticks will behave as you describe. The '166 chip is also a candidate as suggested, but I'd check the stuff between it and the port first.

[alexh]

Battery acid corrosion is the most common reason for failure. Get it open asap

[majestyx]

Even though I had removed the leaked battery and cleaned up the residue months ago, the mouse movement issue just started happening when I originally posted. I'm guessing it did more damage than what it actually looks like. I've sent the motherboard and processor board out for recapping and for work on any additional damage that was done by the battery leaking. Just hoping it can be fixed since other than this, it was working quite smoothly.

[Daedalus]

Yeah, it can sometimes be almost impossible to clear leakage fully from a board. It gets under tracks, under components, into vias, all of which can be very difficult to clean up fully. What little is left will slowly eat away at the traces until one day, maybe years later, something fails. The good news is that such a fault should be a simple enough repair, so don't worry too much

[majestyx]

I ended up sending it to Acill for a complete recap (motherboard and CPU board), battery replacement and mouse port fix. It took awhile to get it back, but then I wasn't in much of a hurry - I'm sure you can tell by how long it took me to follow-up on this post.

Anyway, he got it back up and running like it was brand new. I highly recommend his service and am happy to report it is back to running like the awesome machine I remember it being~!