Smoked my tower amp

[bturner2]

bturner2 - both distribution blocks (ground and power) are located under the observers area next to the amps. I do have a 250A fuse located back by the batteries that "protects" the entire system.

Since my system is 15 years old, I am now thinking of replacing all three amps to small, more efficient components.

I too am interested in what others thoughts are, including MLA. I am going to tear into the smoked amp this afternoon. I'm hoping to find some components (resistors, diodes, etc...) that are toast that may have led to the amp cooking. If not, I work in aerospace and our company designs and builds power distribution and power conversion units running up to 800A at 270DC. We have Chief Engineers that are experts in the area of 28VDC, 115VAC and 270VDC power. Once they see this, they should be able to tell what happened.

I refreshed my 07 X2 system a year before I sold it. I went from the old and heavy JL stock amps to the newer m series 600 and 400 watt amps. The 2 of them fit in less physical space than the 6 channel old amp that came out. Probably weighed a third as much as well and it seemed to run much cooler. Was very happy with the upgrade. Wish I would have saved everything to put back in before I sold it. The new owner could have cared less about the upgrade and stated that he probably wouldn't be using the stereo much. I really could have used those amps for the new boat.

[MLA]

Lots to unpack; The main fuse and distribution block fuses are there to protect the cabling NOT the amp. There are tons of circuits on that PCB that can go up in smoke, create lots of heat, all without presenting a current draw through the power supply that would exceed the upstream fuses. So perfectly normal for those upstream fuses to no blow.

Given the short distance between the amp and block, 4ga would be safe and appropriate. Given the amp's onboard fussing value and short distance of the 4ga, the 125A fuse in the block is within allowable over-fusing guidelines. Me? I would have likely used a 100A.

HTX-4 with 100A fuse and 4ga; The HTX-4 has only 50A worth of onboard fusing, so 100A is 2X what the amp's max is going to be, which unlikely to ever be reached. So a smaller value can be used without fear of the amp ever drawing enough to blow the fuse. As noted earlier, this fuse is not there to protect the amp, its for the cable.

However................not all amps have on-board fuses. For example the Kicker KXMA series. So in this case, that upstream fuse will no protect the cable and amp. So its value needs to high enough to carry the potential load, but not exceed the capacity of the cable.

In the HTX-4 scenario, we know the potential draw, but you will now need to use the length of the 4ga to determine its capacity.

[prostar205]

I opened up the smoked amp and there are no components that show any signs of failure. In fact, my son said the tower speakers still worked, even with the white smoke pouring out of the amp. They only worked on lower volumes.

[bturner2]

Wow that's crazy. Is there anyway something being stored in that area somehow shorted the power to ground externally and we're seeing the damage there? I'm as guilty as anyone stuffing gear in that area for storage as people come aboard. I mean if this didn't blow a fuse anywhere in the system something is seriously wrong with the circuit protection.

I get what MLA is saying about the fuse protecting the wiring but based on the fried ground wire it didn't even do that. I've had several amps trip a breaker as they started to overheat but never had one melt down the face of an amp or fuse. Something happened or isn't right.

[prostar205]

bturner2 - Very unlikely something got close enough to those terminals to create a short. The KX amps have end caps that protect the connections. I was disappointed not to find any burned components inside the amp. What's more - I can't believe the thing still works.

[MLA]

that area somehow shorted the power to ground externally

With 4 ga cable, this scenario would have popped the 125A fuse instantaneously. This would not have cause the ground terminal and onboard fuse damage we see in the pics.

Poor connections can generate a great deal of heat, based on the current passing through it relative to the amount of terminal surface area. Imagine the thickness of the stud ring terminal for an 18 gauge wire, but with the wire end the size to accommodate 1/0 starter cable v's a larger heavy thick ring. The cable size is right, but because the ring on the battery post is so small, you have so little surface are to handle the current. It would likely melt the thin ring terminal.

So a poor connection could possibly cause this type of damage and there not be a short or PCB failure.

I've had several amps trip a breaker as they started to overheat but never had one melt down the face of an amp or fuse

I dont see these two scenarios intersecting. An amp reaching thermal shutdown wont pull any more current then when its in its first 10 minutes of operation. Im also curious how you were able to determine the amps were getting close to thermal shut down when the breaker tripped.

[prostar205]

Poor connections can generate a great deal of heat, based on the current passing through it relative to the amount of terminal surface area. Imagine the thickness of the stud ring terminal for an 18 gauge wire, but with the wire end the size to accommodate 1/0 starter cable v's a larger heavy thick ring. The cable size is right, but because the ring on the battery post is so small, you have so little surface are to handle the current. It would likely melt the thin ring terminal.

So a poor connection could possibly cause this type of damage and there not be a short or PCB failure.

I showed the pictures to a couple of our Chief Electrical Engineers at work. They all agree that it appears this was caused by a loose ground connection. Here are some pictures from the inside of the damage. Again, this amp will turn on and play music through the tower speakers. It just smokes a lot when doing it.

[ShuManChu]

I showed the pictures to a couple of our Chief Electrical Engineers at work. They all agree that it appears this was caused by a loose ground connection. Here are some pictures from the inside of the damage. Again, this amp will turn on and play music through the tower speakers. It just smokes a lot when doing it.

As you have found out, loose connections can cause a lot of heat to build up without exceeding a fuse rating. I suggest you use an appropriate sized ferrule on all future power and ground connections.

See this informative and brief video: https://www.youtube.com/watch?v=sMFFzpzKhFg

When you screw down onto bare wire, initially that connection is tight. After several years of vibration and movement, the individual conductors in the stranded wire will settle and compress, as well as the set screw vibrating loose. Then you get some very high currents flowing through some very high resistance wires and melting will result.

Additionally, I think the 3x 40A fuses on the amp essentially make up a single 120A fuse. So you have a 125A fuse in the distribution block (which, by the way, will not blow at exactly 125A for an ANL style fuse, it takes more than that to make it blow) "protecting" a 4ga power wire going to the amp, and then you have the 120A fuse built into the amp "protecting" the 4ga ground wire.

When that 4ga wire is properly connected and there is nothing loose, then you have a perfectly fine setup, if a little bit close to the max limit as MLA points out. Once that wire effectively becomes less than 4ga (loose connection) then you no longer have fuses that protect the wire, instead the wire itself turns into the "fuse."

While you are picking replacement amps and deciding on what to do with your wiring set up, remember that the amplifier's efficiency needs to be taken into account for designing wire gauges and fuse ratings. Check out this helpful site: https://www.bcae1.com/wire.htm

Using that website and the tables, we can see your kicker amp (the burned up one) is a class AB amp that has a max output of 1700 W (850W x 2). That should require a 2ga wire with a 200A fuse protecting the wire. The amp's built in 120A fuse should protect the amp itself.

If you decide to upgrade your amp to a more efficient class D amp, then you could probably reuse your wiring and fuse setup to power a class D amp with a total output of up to 1355W.