1. Tube replacement: Tubes have a limited lifespan and need to be replaced periodically. Replace them when they become visibly worn or when sound quality is noticeably affected.
2. Cleaning: Dirt and dust can build up inside the chassis and on the circuit boards, so they should be cleaned inside of the amp.
3. Bias adjustment: Proper bias setting ensures optimal tube performance and sound quality. This should be done only by qualified technician.
4. Capacitor replacement: Capacitors in the amp should be replaced periodically to maintain proper voltages..
5. Wiring repair: Loose or damaged wiring and solder joints should be checked and repaired as needed.
6. Plate voltage check: The plate voltage should be checked to make sure it is within the specified range.
7. Power supply check: The power supply should also be checked periodically to ensure that it is functioning properly.
I recommend having your tube amp professionally serviced every two years for the best performance.