Editing Osborne Vixen Troubleshooting Guide (section)

== Component-level Tests ==

=== Clock & Reset Circuitry ===
* Confirm CPU clock (typically 4 MHz) with an oscilloscope or logic probe.
* Check RESET line: should pulse low on power-up, then go high.
* If CPU is not running, check reset capacitor and associated logic (e.g., 555 timer or discrete components).

=== Voltage Test Points ===

{| class="wikitable styled-table"
! Location !! Expected Voltage !! Notes
|-
| CPU Vcc pin || +5 V DC || Main logic supply
|-
| Floppy drive connector || +5 V, +12 V DC || Both required for operation
|-
| CRT board anode || +180 V DC || High voltage—use caution!
|}

=== Logic IC Substitution ===
* Swap socketed logic chips (74LS, 4000 series) one at a time with known-good parts.
* For soldered ICs, piggy-back a good chip to test for improvement (not for MOS/ROMs).