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peb
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PostPosted: Tue Apr 12, 2016 6:22 am   Reply with quoteBack to top

Senior moment, I guess.

Last gig I loaded at least one channel, maybe two, of my DCM2004L below 4 ohms. Ended up having smoke drifting out of at least two monitors (Kustom KPC12M). Pulled the jack plates off of 2 last night, one has a burned resistor (?) and the other appears scorched. Before I drop $20 a pop on replacement jack plates, how can I test the woofer and horn driver? If the woofers are bad, be cheaper to replace the monitor.

Any thoughts on if the amp survived stupidity and how to test it? Before I killed the power, I had clip lights lit on two channels.

I need to go back to a powered mixer, all this rack gear is too much for fesitval and street party gigs.

peb

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tms13pin
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PostPosted: Wed Apr 13, 2016 8:05 am   Reply with quoteBack to top

Testing the woofer drivers is easy. Disconnect them and measure their
DC resistance and you'll be able to tell if the voice coil is cooked. If
it is reading what it should... about 6+ ohms for an 8-ohm driver, then
they are ok. The horn too, depending on what kind they are. If they are
magnetic then the above will work as well. If they are piezo, they are
probably ok as the piezo horns can take a lot of beating.

If there are crossovers inside, these may be cooked.... you said a resistor
you saw was bad. If you're lucky, this is where the smoke came from
and this took the brunt of the power surge.

As for the amps, get some speakers you know are good, turn the volume
all the way down on the amps, and slowly increase it and see if you're
getting signal. If you're getting nothing, check the fuses. With any luck,
between the fuses and the thermal protection built into the amp
circuitry, this stuff kicked in before damage was done. Did you daisy
chain too many monitors?

--Tom
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Brian D
Too Much Free Time


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PostPosted: Wed Apr 13, 2016 9:40 am   Reply with quoteBack to top

I have used a nine volt (9v) battery to test speakers before. Yes, the resistance test is probably better, but if you do not have a meter...

For the 9v battery, placing one side of the speaker on the NEG and the other side on the POS will make the cone either move in or out. Reverse the polarity of the battery or wires will cause the speaker to move in the opposite direction. This will only confirm if the coils are in tact. And only on the subwoofer. You may also hear a pop.

For the tweeters or horns, you may only hear a pop with touching the battery. I have never tried it with tweeters before.

Hopefully you amp has a foldback if the power exceeds manufactured specs. Basically, the amp will shut off. If it didn't then you may not have damaged the amp just pushed it to its outer limits. Clipping lights might come on way before the amp would be in the danger zone. Just might mean you have reached the point of saturation, or reaching its P1dB (1dB Compression Point).

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peb
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PostPosted: Wed Apr 13, 2016 1:20 pm   Reply with quoteBack to top

Tom,

Yes, sadly, that's exactly what I did. Lot's of reasons (or excuses) as to why but bottom line was I thought the amp was rated to 2 ohms. Nope. The DCM2000L we use for mains is but not the DCM 2004L monitor amp.

Cool!

I have a couple of inexpensive multimeters so I'll check the resistance on the speakers and horns. I have another set of monitors at the house so I can test the amp. As many times as I've read how Carvin does a good job on the protection side (for just such senior moments I think), I'm thinking the amp will be OK.

I'll let y'all know what I find out this weekend.

Thanks!

peb

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