Symptoms:

Amplifier consumes approximately 630 mA quiescent current with no load connected.

All driver transistors in the output stage (for all 4 channels) are running hot.

All output transistors, diodes, ICs, and capacitors have already been checked and/or replaced.

Tests Performed:

1. Verified power supply rails are stable and within specification.

2. Checked biasing resistors and emitter resistors for drift or incorrect values.

3. Inspected PCB for possible leakage paths, solder bridges, or damaged traces.

4. Replaced electrolytic capacitors in both power supply and audio sections.

5. Output stage power transistors tested OK (no shorts or leakage).

Issue:

Despite the above, high idle current and overheating of the driver stage persists.

Request:

Looking for guidance on:

Possible causes of excessive idle current in the driver stage.

Recommended next steps for isolating whether the problem is related to bias circuit, thermal tracking, or feedback loop instability.

Please help me

⟐ Edited March 20, 2026 at 19:38 MST