I've also seen the juddering on mice when either the 74LS14 is dead, or the LED isn't properly aligned.
Put X1 and X2 (outputs from the LS14) on a scope and spin the respective axis encoder. You should get X1 leading X2 in one direction and the opposite in the other direction. Do the same for Y1 and Y2 and the Y axis.
If you have no output then do the same, but check the input. The input voltage needs to transition between about 1.2V and 1.6V for the LS14 to cleanly switch. If you have this and one or more of the LS14 outputs are stuck, then replace the LS14 and try again.
You may also need to align the LED. For this, put the 1/2 output of the dodgy axis on the scope. Check you have X/Y 1 leading X/Y 2 in one direction and the opposite in the other. If you're missing one or the pulses are overlapping - grab the leads of the LED with insulated tweezers or similar (to avoid stressing the PCB) and slightly bend its legs. Rinse, repeat.
If you've replaced the LEDs with the Kingbright ones I posted about, then you'll need to modify the PCB... the details should be in at least one of the messages I've posted on the subject.
The RISC PC mice are pretty bad and very cheaply made - the PCBs are not very high quality at all and tracks tend to lift easily, which frigs the LED alignment. I've replaced them with PS2Mouse adapters and decent optical mice on my machines, it's just less stress all round.
Put X1 and X2 (outputs from the LS14) on a scope and spin the respective axis encoder. You should get X1 leading X2 in one direction and the opposite in the other direction. Do the same for Y1 and Y2 and the Y axis.
If you have no output then do the same, but check the input. The input voltage needs to transition between about 1.2V and 1.6V for the LS14 to cleanly switch. If you have this and one or more of the LS14 outputs are stuck, then replace the LS14 and try again.
You may also need to align the LED. For this, put the 1/2 output of the dodgy axis on the scope. Check you have X/Y 1 leading X/Y 2 in one direction and the opposite in the other. If you're missing one or the pulses are overlapping - grab the leads of the LED with insulated tweezers or similar (to avoid stressing the PCB) and slightly bend its legs. Rinse, repeat.
If you've replaced the LEDs with the Kingbright ones I posted about, then you'll need to modify the PCB... the details should be in at least one of the messages I've posted on the subject.
The RISC PC mice are pretty bad and very cheaply made - the PCBs are not very high quality at all and tracks tend to lift easily, which frigs the LED alignment. I've replaced them with PS2Mouse adapters and decent optical mice on my machines, it's just less stress all round.
Statistics: Posted by philpem — Thu Apr 03, 2025 8:50 am