A burning smell, smoke, or visible overheating was noticed.
Safe first checks
Turn the unit off, unplug it, and leave it unplugged.
Do not power it on again to see if the smell returns.
Keep it away from combustible materials and allow it to cool.
If there was smoke, heat damage, or a blown fuse, arrange professional inspection.
Next step
Do not proceed with at-home electrical tests on this symptom.
Bench Technician Steps
This is the model of work a qualified electronics technician follows using the exact service manual and suitable test equipment. It is not a do-it-yourself instruction to work on energized equipment.
Inspect ventilation, heatsink mounting, output devices, emitter resistors, and power-supply components for evidence of heat stress.
Using the service manual, verify bias and DC offset only with suitable instruments, correct test points, and the manufacturer’s procedure.
Do not leave a unit powered and unattended while investigating an overheating or burning-smell fault.