[Coco] CoCo 64K (26-3126) Keyboard Issues Follow-up

[Melanie and John Mark Mobley]

Christopher,

Inductive Signal tracer:
For the AC signal you can likely use an 555/7555 Interred Circuit Resistor-Capacitor timer/oscillator.
The 7555 uses CMOS and may be too delicate to use as test gear.
The Texas Instruments NE555P from Digi-Key is $0.45.

You need to use the inductive signal tracer in an electrically quiet area.  You need to far away from florescent lights and Cathode Ray Tube (CRT) displays.  The inductive signal tracer can be used to locate sources of noise as well.  Some modern Light Emitting Diodes (LED) Edison base lamps used to replace incandescent Edison base bulbs can be noisy.  A good old fashioned incandescent flashlight should be just fine.

-John Mark Mobley