Hi guys,
I have an Alpine MRV-F305 which is cutting out periodically every 5-6 seconds.
Now I know there are about 10,000 "my amp is cutting out" threads out there (and i feel like i have just read half of them) but;
The amp cuts out regardless of volume level.
The amp cuts out regardless of temperature.
The amp does NOT go into protection mode, and holds a constant green (ok) light.
All wiring and settings potential solutions have been exhausted.
I have reason to believe the amp has been water damaged. It is installed in my boat and resides directly underneath 2 cup holders and upon removal of the amp discovered that one of the drain hoses from one of the cup holders has come off, meaning water drops could have drained straight down onto the terminals end of the amp.
I have removed the cover on the amp and cannot find any water or visible water damage, but it was 2 weeks prior that the fault first occurred.
My question is this, if a few drops of water have made their way into the amp and caused a short, how may I go about chasing the damaged component? Will a short in the PS cause a blown transistor like overloading might?
Any details on how to repair would be appreciated.
cheers
Arron
If this belongs an one of the amp specific sections I apologize, please move.
I have an Alpine MRV-F305 which is cutting out periodically every 5-6 seconds.
Now I know there are about 10,000 "my amp is cutting out" threads out there (and i feel like i have just read half of them) but;
The amp cuts out regardless of volume level.
The amp cuts out regardless of temperature.
The amp does NOT go into protection mode, and holds a constant green (ok) light.
All wiring and settings potential solutions have been exhausted.
I have reason to believe the amp has been water damaged. It is installed in my boat and resides directly underneath 2 cup holders and upon removal of the amp discovered that one of the drain hoses from one of the cup holders has come off, meaning water drops could have drained straight down onto the terminals end of the amp.
I have removed the cover on the amp and cannot find any water or visible water damage, but it was 2 weeks prior that the fault first occurred.
My question is this, if a few drops of water have made their way into the amp and caused a short, how may I go about chasing the damaged component? Will a short in the PS cause a blown transistor like overloading might?
Any details on how to repair would be appreciated.
cheers
Arron
If this belongs an one of the amp specific sections I apologize, please move.
Well your probably correct about the moisture damage because this amp was not marine rated it will suffer from the humidity and possibly the salt in the air in any boat situation. These car amps were not meant to be used in boats so they were never conformal coated inside to prevent moisture related failures that I have seen in car amps used in boats.
It all depends on how much exposure its seen over how long of a time. But your guess is very possible as I have seen dozens of car amps brought in from boats with corrosion issues.
Now due to a lack of tech info in your thread post its going to be very difficult to diagnose your amp. Alpine service manuals have a very in depth final test section that I tell folks to look at and do in many cases the failure of this test alignment section will give clues to where your amp is faulting.
I have seen bad solder joints cause issues like you describe, and I have seen defective components cause this also. Amps used in boats tend to be over-driven a lot because the boat has no real reflected sound owners tend to turn them up too high and damage them all because of radiated sound that does not reflect back at the boat. The music carries across the water just fine but in the boat you can't really hear it since it all goes away and little to none of it reflects back at the listener like in a car or truck.
I always ask folks to read the DC voltage present on the speaker terminals with no RCAs hooked and and no speakers hooked up but the amp power on. If the amps in trouble this one reading will likely show that fact as the higher the DC voltage the worse off the amp is internally in most cases.
If your not use to working with electronics then I suggest you start with Perry Babin's training links he has under all of his posts, Its the best free training your gonna find on the web, short of taking a tech training course at your local college.
Your likely gonna have to tear it apart inside and check both sides of the PC board for moisture damage and broken or bad solder joints. I have seen huge water damage under the circuit board with all sorts of shorts and what not. If you go that far please post pics of the amps board both front and back if possible. It helps everyone here when they need to point something out for you to check.
It all depends on how much exposure its seen over how long of a time. But your guess is very possible as I have seen dozens of car amps brought in from boats with corrosion issues.
Now due to a lack of tech info in your thread post its going to be very difficult to diagnose your amp. Alpine service manuals have a very in depth final test section that I tell folks to look at and do in many cases the failure of this test alignment section will give clues to where your amp is faulting.
I have seen bad solder joints cause issues like you describe, and I have seen defective components cause this also. Amps used in boats tend to be over-driven a lot because the boat has no real reflected sound owners tend to turn them up too high and damage them all because of radiated sound that does not reflect back at the boat. The music carries across the water just fine but in the boat you can't really hear it since it all goes away and little to none of it reflects back at the listener like in a car or truck.
I always ask folks to read the DC voltage present on the speaker terminals with no RCAs hooked and and no speakers hooked up but the amp power on. If the amps in trouble this one reading will likely show that fact as the higher the DC voltage the worse off the amp is internally in most cases.
If your not use to working with electronics then I suggest you start with Perry Babin's training links he has under all of his posts, Its the best free training your gonna find on the web, short of taking a tech training course at your local college.
Your likely gonna have to tear it apart inside and check both sides of the PC board for moisture damage and broken or bad solder joints. I have seen huge water damage under the circuit board with all sorts of shorts and what not. If you go that far please post pics of the amps board both front and back if possible. It helps everyone here when they need to point something out for you to check.
Thanks for you reply 1moreamp. I know my way around a multimeter but do not have great experience with amplifiers. I know the easiest thing to do would be to replace the amp as it isn't worth much, but what would I learn doing that? So thanks for pointing me in the right direction without judging.
I have pulled the amp apart and can not see any evidence of water damage or corrosion (though am I not an expert). Moisture in the air obviously can be an issue anywhere in a boat. For the record, the boat is a freshwater boat, and the there is no chance of direct water contamination, with the exception of the unfortunate event of the cup holder drain being missing.
Here is the board:
I have pulled the amp apart and can not see any evidence of water damage or corrosion (though am I not an expert). Moisture in the air obviously can be an issue anywhere in a boat. For the record, the boat is a freshwater boat, and the there is no chance of direct water contamination, with the exception of the unfortunate event of the cup holder drain being missing.
Here is the board:
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
Last edited:
1moreamp, I tested the voltage at the speaker terminals with nothing but power connected and got <0.1VDC on each channel.
I don't know you opinion on checking FET's with a multimeter (as i have read it cannot be done, but now read it can) but have found a repeatable anomaly with one channel's FET's.
I don't know you opinion on checking FET's with a multimeter (as i have read it cannot be done, but now read it can
) but have found a repeatable anomaly with one channel's FET's.
Fets have a capacitive effect on their gates.Some times they must be switched off before they can be tested.
Using a DVM on an N channel FER, measure Drain(+ve lead) to Source (-ve lead). Hold the lead on the Source whilst touching momentarily the gate with the other probe and quickly watch for the decay as the probe is placed back on the Drain.
A bit crude but it will tell you if the FET is damaged.
Using a DVM on an N channel FER, measure Drain(+ve lead) to Source (-ve lead). Hold the lead on the Source whilst touching momentarily the gate with the other probe and quickly watch for the decay as the probe is placed back on the Drain.
A bit crude but it will tell you if the FET is damaged.
Yes, it was like the amp was reset/rebooting every time.
The tests I am conducting on the FET are admittedly in situ rather than isolated, but the channel in question repeatedly shows a short on one of the FETs from source to gate and source to drain, when none of the other output FETs do. Just say the word and I will disregard this idea/or remove the FET's and conduct an isolated test.
I wish I could say 100%, like I said, I don"t have a great deal of experience with amplifiers. I am assuming the ones at the top of the first image are the the PS FETs and the 8 across the bottom in pairs are the output FETs.
I can't say for certain that all 4 channels were outputting correctly, I will check this.
Perry, I'm not sure what a Qx01 is so i tested the smaller transistor that accompanies each channel and I get -VDC on leg 3 of each with or without signal connected.
I'm not sure if this helps or not but I did make this observation:
The little red LEDs on the board that light up when playing. The LED that matches the FET I found shorted does not turn on and off with the others.
Basically the other 3 LEDs turn on when the music is playing then turn off when it cuts out.
The one in question tries to turn on but immediately turns off, and then as all of the others turn off it flashes quickly then dies with the rest of them, accompanying this flash is a "pop" from the speakers.
I'm not sure if this helps or not but I did make this observation:
The little red LEDs on the board that light up when playing. The LED that matches the FET I found shorted does not turn on and off with the others.
Basically the other 3 LEDs turn on when the music is playing then turn off when it cuts out.
The one in question tries to turn on but immediately turns off, and then as all of the others turn off it flashes quickly then dies with the rest of them, accompanying this flash is a "pop" from the speakers.
OK, so i removed the suspect FETs and found them to still have the same diagnosed problems as before.
I plugged the amp in and the remaining 3 channels now play perfectly.
Now, are there any other components i should be checking before simply replacing these two FETs?
The FETs are NEC J302 and NEC K1287, where might I find suitable replacements? probably online as my local electronics store is not very comprehensive.
I plugged the amp in and the remaining 3 channels now play perfectly.
Now, are there any other components i should be checking before simply replacing these two FETs?
The FETs are NEC J302 and NEC K1287, where might I find suitable replacements? probably online as my local electronics store is not very comprehensive.
Qx01 is shorthand for Q101, Q201, Q301...
Those may be difficult to find. Add a 2S prefix when searching. The IRF540 and IRF9540 may work as subs.
It's strange that that channel could produce audio with shorted output transistors. Shorted transistors would tend to drive rail voltage to the speakers or cause the amp to draw excessive current.
Those may be difficult to find. Add a 2S prefix when searching. The IRF540 and IRF9540 may work as subs.
It's strange that that channel could produce audio with shorted output transistors. Shorted transistors would tend to drive rail voltage to the speakers or cause the amp to draw excessive current.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.