Amiga 1000 mouse not working

[vic20owner]

I recently purchased this Amiga 1000.  It did not boot but after replacing a CIA it boots.  The keyboard works, external floppy works, but mouse does not work. I connect the mouse to an external power supply, and an oscilloscope and I can see a pulse train when I spin the ball. So mouse APPEARS to work.

I examined all caps on the motherboard and see no signs of leakage or bulging.   The machine shows no symptoms of bad caps other than the mouse.

Anyone know which likely causes are of the failure to detect mouse movement? Both buttons work, but no movement.  IC22 (74HC157) is the only thing which stands out. Could also be cracked solder joints at the port.

Thanks

[Steady]

Does a joystick work properly on that port?

[Steady]

Also, swap CIAs and see if you get different or same symptoms.

[mykrowyre]

Hi, I did swap CIA's and no mouse improvement.  Will check with a joystick.

I just had a look at how the mouse signals are sent and it looks like there are two signals per axis, slightly out of phase to show direction.

I didn't think to examine both (all four) so I'll have to examine it again.

[mykrowyre]

Oops just noticed I logged in with my old 8 bit username last time.. oops!

Didnt realize I had both names registered.

The port did work with a joystick so I ruled out the Amiga.

I had another look at the mouse and found that there was no PWM signal on the V/H/VD/HD pins.

I verified that the LED and optical sensors were working and concluded it was the quad comparator in the mouse that was bad.

I removed it and placed it in a breadboard and sure enough it's dead.

I have a replacement mouse on the way until i can finish the repair of the original.

thanks

[JimS]

check to see if you have 5v on the power pins of the joystick port. i think it's the center two pins of the bottom row of the db-9 connector. Later Amigas had a pico fuse in the 5v line, but the 1000 didn't. It can vaporize a mobo trace if something shorts the mouse port. The mouse buttons and joysticks will still work, cuz they're just switch closures.