Blaupunkt MPA 400US manual Trouble-Shooting Guide, this is generally a RADIO installation, problem

TROUBLE-SHOOTING GUIDE

Below is a basic trouble-shooting guide to assist in seeking out and correcting a problem that may occur in the installation process. Although lengthy, this chart cannot address every single problem possible but mainly the ones most common.

SYMPTOM	PROBABLE CAUSE OR CORRECTION
No power (power light not on)	■	Check connections to amps +12 volt, ground, and remote lines.
	■	Use voltmeter to verify voltages are at terminals of amp.
	■	Check main power connection at battery.
	■	Check fuse in power line at battery.
	■	Disconnect all speakers but not power lines - if unit then turns on, a speaker short
		or speaker line touching vehicle chassis is likely.
Power but no sound (power light is on)	■	Check all input cable lines for connection.
	■	Disconnect speakers from amp, test speaker lines with digital voltmeter to verify >2
		ohms per channel (non-bridged mode).
No sound from one channel or entire side	■	Check radio’s balance and fader control positions - verify they are at center.
	■	Check speaker connections at amp and speaker.
	■	Check input leads for connection to amp.
Very low sound level	■	Verify radio balance and fader controls are at center positions.
	■ Check amplifier’s input gain control setting - adjust for higher output levels if
		necessary (gain settings closer to 0.3 volts).
	■	Receiver may have very low output voltage levels - a step up “line driver” may
		have to be used.
Power amplifier turns on and off repeatedly	■	Make sure power connections at batter are tight.
(motor-boating sound)	■	Verify battery voltage is >11.5 volts DC (12.5-15V engine on) at amplifier with engine off.
	■	Check all radio and amplifier ground connections.
Amplifier turns off during loud or distorted	■	Input stage being over-driven - lower input gain (closer to 4 volt setting).
passages	■	Verify battery voltage is >11.5 volts DC at amplifier with engine off.
	■	Check all radio and amplifier ground connections.
	■	Verify speaker loads >2 ohms on all channels (non-bridged mode).
Amplifier performs fine but gets very hot to	■	Input gain control too high - lower accordingly (closer to 4.0 volt setting).
the touch	■	Verify speaker loads >2 ohms on all channels (non-bridged mode).
	■	Verify the mounting location allows for free air movement around the amp.
		Preferably, the amp should be mounted with fins up and down so rising heat moves
		quickly away from amp.
Amplifier turn-on/turn-off pops or noises	■	“turn on race” - disconnect trigger from radio and turn on/off via a wire jumper to
		power terminal. If noise goes away, the radio is turning on/off too slowly. This is
		radio problem and can only be corrected with outboard turn-on delay relay system.
	■	Radio “thump” - disconnect the RCA input lines to the amp and turn on/off via radio
		trigger. If noise goes away without RCA lines connected, the radio is sending pops
		out through RCA lines. This is a radio problem and can only be corrected with
		outboard turn-on delay relay system.
Cracking noises on AM/FM radio but not	■	Ensure the problem is “radiated noise” by placing a portable FM radio near the car
on tape or cd.		engine. If noise is picked up, then it is a vehicle problem and not your system.
		Research to isolate the source and properly shield or bypass.
	■	Are spark plugs and wires > 3 years old? These can often radiate substantial noise
		when old.
	■	Verify the engine block has a good ground connection to chassis ground.
	■	Verify the engine compartment hood is grounded to vehicle chassis via a braided
		grounding strap.
Whining noise, engine running, varies in	■	Verify all power and ground connections are clean at radio.
pitch or loudness with engine speed, AND	■	Re-route radio power and ground so they are sourced from same connections back
varies with radio volume control setting		at amplifier (this is called a “common” ground).
(this is generally a RADIO installation	■	Check all ground connections to ensure clean surfaces that have all paint removed
problem)		and also not oxidation buildup over time.
	■	Verify there is some kind of power filtering choke assembly at back of radio. If not,
		install one.
Whining noise, engine running, varies in	■	Check battery ground connections at chassis are clean and tight, scraped free of
pitch or loudness with engine speed, BUT,		oxidation, paint, and grease.
DOES NOT vary with radio volume control	■	Re-route radio power and ground so they are sourced from same connections back
setting (this is generally an amplifier		at amplifier (this is called a “common” ground).
installation problem)	■	Bypass all equipment between radio and amp (e.g., equalizers) directly connecting
		radio. If noise goes away, signal processor has problem.
	■	Check for signal level “ground loops” - disconnect the outer shield of the RCA cable
		at one end of the cable (e.g., radio end). If noise goes away, modify cables
		accordingly. There are voltage differences at the ground connections of the
		components and these are NOT correctable any other way than such shield cutting
		or an outboard “ground loop isolator” which is a small transformer.

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