Burned amp?

[Duncan]

First real day out on boat yesterday. WS 12 sub powered by bridged Syn2 worked about 8 minutes -- then I smelled burning plastic from amp wall. Sub no longer putting out sound. The amp was still powered up.

Any troubleshooting tips? I assume it is fried. By I will check fuses. What can I check with multimeter? Voltage across output?

[chpthril]

I would first disconnect the sub at the amp and measure its impedance. Next, push the cone in and let it return. It should have some resistance, but move free and smooth with no funky noises.

If the amp is powered up, with either the blue (normal) light or the red (protect) light on, indicates there are no blown fuses, but testing the voltage at the amp and its internal fuses never hurt. Before putting a load back on the amp, I would inspect real close, to see where that source of the smell was. Was it internal of the amp or external like from behind the amp wall.

The last thing i would do, depending on whats found up til now, is either put another sub on the amp as a test or switch it to hi-pass, wire up a full-range speaker, bottom the gain and just see if it has any output on the chnls.

[Duncan]

Thanks for the tips.

Smell was from inside Syn2. Sub cone moves freely.

I think I tracked down the problem. Season before last, I had the dealer put in the new sub and build an enclosure. They built an enclosed rather than ported and the dimensions were a little small for enclosed. So this last off season, I asked them to stuff the box with some polyfill to account for small size.

When I opened up the box today, I pulled out a full kitchen bag trash bag full of polyfill. No way any more could have squeezed in there. I am guessing there was so much poly, the cone couldn't move and the load on the amp fried it. Wonder why no protective circuits or fuses kicked in? Is this theory plausible?

[Duncan]

Impedance of disconnected sub showed about 7.5 ohms.

(Sub cone moved freely after pulling poly fill -- did not check before.

[chpthril]

If your sub is a 4 ohm DVC wired in series, then its spot on @ 7.5 actual. Crammed full of polly-fill would certainly kill the sub's performance, I do not see that in itself, causing undo stress on the amp. This being that the bridged load, the sub, is half of what the amp can handle. Although the amp MAY have been letting the smoke out, it is entirely possible to have the current load not exceed the circuit protection yet.

If you deem the amp is toast, let me know. Rewiring that sub from 8 ohm to 2 ohm and feeding with 2X the power from the right amp would be a world of difference.

[Duncan]

Could the amp fry while not exceeding the current load?

Might have to take up your suggestion re amp options.

[chpthril]

Yes. Any number of small components on the PCB could fail, yet the amp's current draw not exceed the fusing.