Editing Apple Desktop Bus Mouse (section)

=== Diagnostic Procedures ===

==== Erratic Cursor Movement ====
'''Symptoms:''' Jumpy, inconsistent, or drifting cursor movement

'''Root Causes & Solutions:'''
# '''Dirty encoder wheels''' (Most common)
#* Remove ball and inspect encoder wheels for dust/debris
#* Clean wheels with cotton swab and 90%+ isopropyl alcohol
#* Use compressed air to clear encoder slots
#* Ensure LED/phototransistor pairs are clean

# '''Worn ball surface'''
#* Check for flat spots or uneven wear
#* Clean ball with isopropyl alcohol
#* Replace if severely worn (19mm rubber-coated steel ball)

# '''Encoder wheel damage'''
#* Inspect for broken or bent encoder wheel teeth
#* Check encoder shaft for excessive play
#* Replacement requires donor mouse or compatible encoder assembly

# '''Controller chip issues'''
#* Test with known-good ADB system
#* Check for proper +5V supply at controller
#* Controller replacement requires exact matching part

==== Button Failures ====
'''Symptoms:''' No click, stuck button, double-clicking, intermittent response

'''Microswitch Testing:'''
# Measure resistance across switch terminals (should be <1Ω when pressed)
# Test for proper tactile feedback and audible click
# Check for mechanical obstruction in button mechanism

'''Replacement Procedure:'''
# Compatible switches: Omron D2F-01, D2F-01F, D2F-01F-T
# Specifications: SPDT, 10mA minimum current rating
# Desolder old switch carefully to avoid PCB damage
# Install new switch ensuring proper alignment with button actuator

==== Complete Failure ====
'''Symptoms:''' No response, system doesn't recognize mouse

'''Systematic Diagnosis:'''
# '''Power verification'''
#* Measure +5V at pin 3 of ADB connector
#* Check ground continuity at pin 4
#* Typical current draw: 50-80mA during operation

# '''Cable testing'''
#* Check for breaks at strain relief points
#* Test continuity of all four wires end-to-end
#* Common failure point: cable entry to mouse body

# '''ADB communication test'''
#* Use oscilloscope to verify data signal on pin 1
#* Check for 800μs attention pulse from host
#* Verify mouse responds with register data when polled

# '''Controller diagnostics'''
#* Check crystal oscillator (if present) for proper frequency
#* Verify controller power pins (+5V and ground)
#* Test for shorts on data lines