ASA Electronics MS-407 - Manual (Page 9)

Radio Balance Check radio function
Speaker Disconnected Check speaker connection at
radio and/or speaker
Only one channel (right or left
side)
Speaker lead shorted or
grounded Check speaker wiring continuity
to ground w/tester or meter
Popping in one or both channels Speaker wiring shorted or
positive lead grounded
Speaker terminals grounded or
shorted
Leads from speaker cone to
terminal touching metal basket