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Page 10 of 12 SC-550-10 28 Volt Installation and Operating Instructions
05/07/05 CP4945A
SERVICE
This unit is designed to provide years of reliable service under even the worst conditions. Many
times there may appear to be a problem with the unit when the true problem is in the speaker(s),
controlled devices, or improper installation. The following chart shows typical symptoms and
possible causes.
A blown siren fuse doesn't necessarily mean that the unit is bad. If a speaker or speaker lead is
shorted the fuse will blow before the unit is damaged. Disconnect the SPKR leads and replace
the fuse. If the unit itself emits a low level sound when in the Yelp position it is OK. Check the
speaker(s) or leads for possible shorting.
25A Fuses are required for each light control output. Adequate fuse rating is required to prevent
overheating of the output connection block.
PROBLEMS
Symptom Possible Cause Check
No power or siren
output
Power switch not turned on
Bad Speaker
Connector or connections loose
Siren fuse blown
Loose connection at power source
Does backlighting come on?
Do you hear a "pop" when turned on?
With siren on, yelp selected, listen for tone in amplifier.
Is an external fuse or circuit breaker used?
Are the power leads connected to a good buss?
No siren tone -
PA works
High Voltage Protection
PA PTT button stuck
Cutout activated
Cutout Polarity Option set wrong
The input voltage must be less than highest rating.
Does PTT button release properly?
Does the siren work when Cutout input is disconnected?
Is the Cutout Input Polarity option properly configured?
No PA PA volume not set properly Have you tried turning the PA volume control?
Distorted siren
sound
Speaker assembly loose
Intermittent Aux Input connection
Low vehicle voltage
Is the speaker bell or tip loose?
Is the Aux Siren Input used and wired properly?
The input voltage must be greater than lowest rating.
Intermittent siren
tone
High Voltage Protection
Connector or connections loose
Loose connection at power source
PA PTT button activation
Circuit breaker in supply connection
Is the vehicle voltage regulator working properly?
Is the connector tight on the back of the unit?
Check for loose leads back to power source.
Is something lying on the PTT button?
Is a circuit breaker used with at least a 50A rating?
Horn function
stuck on or
Manual or Phaser
stuck on
Siren button switch stuck
Aux Siren switch stuck
Aux Input improperly connected
Aux Input Polarity Option set wrong
Does the Siren button switch return fully when released?
Does the Aux Siren switch return fully when released?
Is the Aux Siren Input used and wired properly?
Is the AUX Siren Polarity option properly configured?
No Radio Unit not connected to radio
Radio volume too low
Is the radio connected properly to the unit?
Can you here the radio in the vehicle?
Have you tried setting the Radio Volume Adjust?
Wrong siren tone Two-Tone option selected Is the Two-Tone option set?
Phaser not work-
ing
Phaser disabled Is the Phaser Disable option set?
Horn not working Horn disabled Is the Horn Disable option set?
Manual stops
immediately
Short Manual enabled Is the Short Manual option set?
Automatic Siren
not working
Automatic Siren disabled Is the Automatic Siren Disable option set?
Light Output not
working
Light Control Output fuse blown
Internal relay contacts bad
Is the light or device shorting?
Is the output current limited to 20A?
Light Output stays
on
Internal relay contacts fused from
overheating
Is the output current limited to 20A?
Non-progressive
output not work-
ing
Internal switching transistor bad Is the external relay coil shorting?
Is the output current limited to 500mA?
Slide switch
outputs turn on in
wrong order
Slide Switch is reversed Is the Slide Switch Reverse option set?