Hi,
I have a NVX JAD900.5 amp that I'm using in a 2.1 configuration in my Chevy truck. Left/Right Front and Single Subwoofer.
For no apparent reason, the LR channels turn off while the subwoofer stays on. It has nothing to do with overheating (I don't think) because it will be off when I start the truck after it has been sitting for hours and then after several minutes the LR will come back on. The subwoofer never shuts off. I believe that if it were an overheating issue, the entire amp would shut down, not just the L/R channels. I have used this amp with a different head unit with the same results, so it isn't the source.
I have 2 options. Take the cover off and try to figure out what part(s) is/are failing or throw it in the landfill and buy a new amp. I'd like to try option 1 first. I'm pretty capable of doing repairs but need some guidance as to what to look for. I don't want to spend a lot of $ on this amp even though when it works, it sounds excellent. Any ideas?
Thanks in advance.
I have a NVX JAD900.5 amp that I'm using in a 2.1 configuration in my Chevy truck. Left/Right Front and Single Subwoofer.
For no apparent reason, the LR channels turn off while the subwoofer stays on. It has nothing to do with overheating (I don't think) because it will be off when I start the truck after it has been sitting for hours and then after several minutes the LR will come back on. The subwoofer never shuts off. I believe that if it were an overheating issue, the entire amp would shut down, not just the L/R channels. I have used this amp with a different head unit with the same results, so it isn't the source.
I have 2 options. Take the cover off and try to figure out what part(s) is/are failing or throw it in the landfill and buy a new amp. I'd like to try option 1 first. I'm pretty capable of doing repairs but need some guidance as to what to look for. I don't want to spend a lot of $ on this amp even though when it works, it sounds excellent. Any ideas?
Thanks in advance.
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If no one offers any suggestions, post good quality photos of the inside of the amp.
Are you sure that the problem isn't signal related, speaker related or a problem with a dirty pot or switch? If you're not sure about the latter, operate all controls through their entire range to see if it makes the channel become intermittent.
Are you sure that the problem isn't signal related, speaker related or a problem with a dirty pot or switch? If you're not sure about the latter, operate all controls through their entire range to see if it makes the channel become intermittent.
Thanks for the reply Perry.
I have tried some of the switches on the amp (thinking it was the front L/R and not the Rear L/R that was going on and off) but I'll try again using more force with the switches since that sometimes helps if there's corrosion build up. I will post photos when I get a chance to open the cover.
I should have been more clear about using a different head unit. The amp was used in a different vehicle in a entirely different system. It was originally used in my Ford Fusion when it started this behavior. I replaced it. I then used it in the system I built for my truck. The reason I was willing to use it in my truck is because I thought the problem was that it was overheating and would shut down when it did. I don't drive my truck very often, or very far when I do, so I thought it wouldn't (or rarely) get hot enough to have this happen. The new amp in my car has never shut down. This is the reason that I know that it isn't the speakers or connection.
I have tried some of the switches on the amp (thinking it was the front L/R and not the Rear L/R that was going on and off) but I'll try again using more force with the switches since that sometimes helps if there's corrosion build up. I will post photos when I get a chance to open the cover.
I should have been more clear about using a different head unit. The amp was used in a different vehicle in a entirely different system. It was originally used in my Ford Fusion when it started this behavior. I replaced it. I then used it in the system I built for my truck. The reason I was willing to use it in my truck is because I thought the problem was that it was overheating and would shut down when it did. I don't drive my truck very often, or very far when I do, so I thought it wouldn't (or rarely) get hot enough to have this happen. The new amp in my car has never shut down. This is the reason that I know that it isn't the speakers or connection.
I cracked it open and it didn't take long to find the likely culprit. One of the large capacitors is fried. So bad that I can't read what's printed on it in order to get the correct replacement. Fortunately there's another one next to it that appears to be exactly the same. Hopefully replacing the fried cap will solve the problem. I wonder if the other identical cap is for the subwoofer channel and that is why I never lose that channel. If that's the case, is the other cap possibly a different value? Another question, why would it work intermittently if the cap is that fried.
Thanks again for your replies.
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Thanks again for your replies.
An externally hosted image should be here but it was not working when we last tested it.
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Rarely is the cause of the issue readily visible with electronics. There will be more to this rabbit hole than the obviously damaged components. Remove or replace the damaged cap and see if the problem persists. Do you have a way to power the amp and diagnose the problems other than just visually?
I disagree. I have repaired several TVs with only visual inspection looking for bulging caps. I have saved hundreds of $ and prolonged the life of some TVs that were headed to the landfill. I believe that this amp will fall under this category of a visually blown cap. It's definitely possible that there's something else wrong, but I'm betting the blown cap is the problem. We shall see.
That resistor next to the relay and capacitor runs very hot. I've seen them melt the relay.
The capacitor doesn't really look damaged. The adhesive from the label looks like it got hot. I expected to see the amp filled with paper fibers from the capacitor exploding.
If cleaning the switches doesn't help, (gently) try moving the various boards around to see if that brings the sub channel back.
The capacitor doesn't really look damaged. The adhesive from the label looks like it got hot. I expected to see the amp filled with paper fibers from the capacitor exploding.
If cleaning the switches doesn't help, (gently) try moving the various boards around to see if that brings the sub channel back.
I do have a way to power the amp outside the vehicle (Jumper Cables and wire) but no way to diagnose otherwise. A friend of mine is an EE and willing to help, but other than that, not much. He works at FLIR where they build infrared and thermal cameras, so someone there might be capable of diagnostics. I'll replace the blown cap and see how it goes from there.
Thanks jkro
I found some notes that stated that the output filter inductors sometimes intermittently short. Circled in photo. Do you see any chafing where the terminal windings meet the rest of the windings?
The relay in this one is much smaller than in other, similar amps. It could be a weak point.
The relay in this one is much smaller than in other, similar amps. It could be a weak point.
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I disagree. The capacitor is completely black whereas the one next to it is bright orange. They are the same cap. The stock photo shows what it should look like. You need to look at the second photo where you can see the side of the cap. Totally black.
I'll look at the winding tho.
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That amp looks like it has duel power supplies. They might be be in parallel, or independent and running different channels of the amp. So its possible one set is getting shut down and the other is not. I have some trouble shooting videos that might help, and one series is a 5 channel amp that has duel power supplies (the Arua amp). YouTube
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