Classe Audio CA-100-101, Service Manual

PRO-SVR_LEGACY    

Page 7 of 14 

Troubleshooting Guide

Symptom Possible 

cause 

Unit won’t turn on 

Check connections; 
Check fuses; 
Check soft-start circuit; 
Check relays; 
Check power supply circuits (positive rail, negative rail, Mosfet 
supply). 

Smoked and/or burned 
components 

Check for short between components and ground; 
Check output transistors; 
Check output relays; 
Check power supply circuits (positive rail, negative rail, Mosfet 
supply). 

Blown fuses 

Check for short between fuse and ground; 
Check power supply circuits (positive rail, negative rail, Mosfet 
supply). 

No output 

Check connexions; 
Check output relays; 
Check power supply circuits (positive rail, negative rail, Mosfet 
supply);
Check output transistors. 

Unit turn into protection 

Check for smoked and/or burned components; 
Check power supply circuits (positive rail, negative rail, Mosfet 
supply);
Check source and load; 
Check protection circuit; 
Check sensor wires between sensor PCB and control PCB; 
Check outputs transistors and Mosfet drivers. 

Excessive buzz and/or hum 

Check electrical lines; 
Check for a ground loop in the system. 

Oscillation Check 

source; 

Check capacitors on main board; 
Check 4.7

ƻ

 resistor. 

Intermittent signal 

Check connections; 
Replace shield wires.