8.9 Troubleshooting by stages

I declare: solidlikelyshaky

1. Read a service manual: schematic, reference voltages, test points, adjustment procedure.
2. Isolate a stage by breaking the chain (lift a coupling capacitor, open a jumper) and test it alone.
3. Follow a signal injected from the generator stage by stage and find where it dies or distorts.
4. Compare measured DC voltages to the schematic’s and say what a deviation means at that spot.
5. Decide what gets repaired, what gets replaced by block, and what’s no longer worth the hour.
6. Diagnosis: a multi-stage device with a vague symptom ("it crackles sometimes"), the method that corners it: heat, vibration, signal, one stage at a time.