Protection circuit "ON" : no sound

Sounds like the fault-protection function is doing its job.
Check loudspeakers are correct impedance and connected to amp.
Make sure there are no stray wire strands shorting these.
Otherwise the amp has an internal fault somewhere.
The relay coil is controlled by the protection circuit.
When the circuit detects any abnormal parameter it triggers an automatic shutdown.
Do you see any error codes flash up when this happens?

Honestly, if you are talking about the speaker protection relay, the relay and associated circuits rarely go bad but instead respond to problems elsewhere in the amp. Anything from defective speakers, bad spkr. wiring to output transistors will cause this protection relay to not energize thus protecting the output stages and speakers.

Not unless you are willing to risk electrical damage or a fire! A fuse is a protection device that is designed to blow if the amp load in a circuit exceeds the "safe" limit for that circuit. Fuses are built with a specific amp rating which is marked on the fuse. The wiring and design load of the circuit dictates the size of fuse that's required to protect the circuit. Circuits that draw a lot of power need fuses with high amp ratings (20 or 30 amps) while those that use minimal power require smaller fuses (5 to 15 amps).

When the current in a circuit exceeds the normal limit for whatever reason, the metal element in the fuse melts and opens the circuit stopping the flow of current. A short, for example, causes a runaway electrical current. If not stopped, wires can start to melt and things can catch on fire. So respect the amp ratings specified for fuses (which can usually be found in your vehicle owners manual, on the fuse block itself or a fuse block reference decal).

What happens if you install a fuse with the wrong amp rating? If you install a 20 amp fuse in a circuit designed for 10 amps, you're asking for trouble. A difference of 10 amps might not sound like much, but it may be enough to fry a sensitive electronic component or to overheat wires to the point where the insulation may start to melt.

WARNING: Under no circumstances should you ever bypass or eliminate a fuse. No electrical circuit should ever be operated without fuse protection. This is extremely dangerous, especially if you've had problems with a fuse blowing before.

If a fuse keeps blowing, it usually means something is amiss in the circuit. The wiring should be checked along with the components in the circuit to determine if there's a short or other problem.

The fuse for the windshield wiper circuit, for example, may blow if ice or debris builds up in the cowl areas and interferes with the movement of the wiper arms. If a fuse blows in a motor circuit (heater blower motor, cooling fan motor, power seat or window, electric fuel pump, etc.), it often indicates a shorted motor. If a fuse in a light circuit blows, look for wiring or connector shorts. Adding driving lights may also overtax the headlight circuit unless a separate circuit is provided for the driving lights. An A/C fuse will blow if the system is low on refrigerant and is working unusually hard, or if the compressor is hanging up. Stereo systems with high amp boosters should also have their own electrical circuit with fuse protection to avoid overloading the normal radio circuit.

A large amp like this likely has protection circuit (probably a relay) that doesn't connect the speakers until the amp is stable and balanced. You relly need the schematics for the amp.

Start looking at your safety circuits.

1. High water temp
2. Low Oil
3. Low water etc...

From the manual these are the protection circuits.

• Engine protection: low oil pressure, high engine temperature.
• Genset protection: under/over voltage, overload, battery charger failure, battery voltage out of limits,
under/over frequency, start failure.
• Circuit breaker protection: IV poles.
• Differential protection.


Any one of them will trip the fuel relay closed. What you may be able to do is disconnect one at a time each protection circuit and see when the fuel relay opens. (Make sure to reconnect each one if it had no effect on the fuel solenoid)

Once you isolate which circuit it is in then you can chase wires or change the bad switch.

Thanks for choosing FixYa.

Kelly

you don't want to do this( bypass the protection0
that d.c. output will burn the coils in your speakers with out making a sound!! you have a biasing problem
or like you said a d.c. offset problem it is best to work on this problem with out a load on the amp, this will allow you to trace back where the trouble is starting at. caps will cause this sort of problem but leaky transistors can also do this, even diodes.
this will require an experienced trouble-shooter.

short answer yes... Long answer... Amp Failure: There are many different ways that an amp can fail but the two most common failures are shorted output transistors and blown power supply transistors (< those are not blown). There are several types of protection circuits in amplifiers. The most common are over-current and thermal. The over-current protection is supposed to protect the output transistors. Sometimes it doesn't work well enough to prevent the failure of the output transistors but it will work well enough to shut the supply down before the power supply FETs are destroyed. If the amp remains in protect mode, goes into protect mode or blows the fuse as soon as the remote voltage is applied, shorted output transistors are almost certainly the cause. If the fuse protecting the amp is too large, if the protection circuit doesn't respond quickly enough or if the power supply is poorly designed, the power supply transistors may fail. If you see a lot of black soot on the power supply transistors (near the power transformer), the power supply transistors have failed. Soot on the board doesn't necessarily mean the transistors have failed. Sometimes, technicians don't clean up the mess from a previous failure. Transistor Failure/Checking Transistors: In general, when a transistor fails, it will either short (common for output AND power supply transistors) or open (common for power supply transistors). Transistors act like valves. They control the current flowing through a circuit. A shorted transistor acts like a valve that's stuck open (passing too much current). In the case of an output transistor, the shorted transistors tries to deliver the full rail voltage to the speaker output terminal. If you've ever seen a damaged amp that pushed or pulled the speaker cone to its limits when the amp powered up (common on some Rockford amplifiers), that was almost certainly due to a shorted output transistor. When checking transistors, you most commonly look for shorted connections inside the transistor. You do this by using a multimeter to look for low resistance connections between the transistor's terminals. Note: I used the terms short and open on the previous paragraph. A short (short circuit) is a path through which current flows that should not be there. An open (open circuit) is a break in the circuit. It is most likely the power supply that has taken a ****.

you have real problem in safety contol circuit which shut down the unit to protect the amplifier from damage

The protection circuit is self resetting, it operates only when there is a fault condition in the amp. there is most probably a failure in the output stages of the amp causing a dc offset condition in the speaker output. The protection cct operates to prevent damage to your speakers. It may be difficult to offer a solution to you for this, it gets a bit complex to fix from here...you may have dry solder joint problems in the output stages, or more likely, failed output components. if you have a transistor checker(ohms meter), then you may be able to determine if any output transistors have failed, I recommend taking the amp to a good HiFi guy for repair. Many (including myself) often replace the all transistors to the last 2 stages when outputs fail. assures reliability in the future to repair this way, but the cost goes up a bit also. expect at least $120 to repair is it is a failed output stage.