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-   -   Help! Weird behaving Amp and Speaker combo (http://www.diyaudio.com/forums/pa-systems/228894-help-weird-behaving-amp-speaker-combo.html)

thuzmund 29th January 2013 04:41 AM

Help! Weird behaving Amp and Speaker combo
 
I was given a integrated PA unit--the kind with power and speaker in one box. It even has a battery for portability! Cool! The old owner said the power would turn off sometimes....so, I took it all apart to look for loose connections or anything visually obvious. Checked out OK.

The speaker box has a subwoofer and a high-frequency tweeter. The tweeter has a connector allowing two sets of speaker wires. Only one was connected when I got it.

Here's the weird issue: If I connect that additional set of speaker wires, the amp light will glow very weakly and not turn on enough to produce any sound. If those same wires are not connected, the amp will turn on and produce sound.

1) Any idea what's going on? :)
2) I imagine that the second set of speaker wires has to do with a frequency splitter and leaving it disconnected will result in crappier sound (it seemed a bit low and muffled to me during voice testing). Does that sound about right?

Here is a pic of what I'm talking about: Image - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

I really appreciate any wisdom that's shared with this amateur musician!

JMFahey 29th January 2013 05:07 AM

Quote:

Here's the weird issue: If I connect that additional set of speaker wires, the amp light will glow very weakly and not turn on enough to produce any sound. If those same wires are not connected, the amp will turn on and produce sound.

1) Any idea what's going on?
Yes , stop messing with it, you have no clue and will burn it.
You are shorting the red/black battery wires across those tweeter connectors.
You have already burnt the tweeter, hence the "muffled sound".

mickeymoose 29th January 2013 10:55 AM

but I did like the sparks and the smoke...

JMFahey 29th January 2013 03:40 PM

Hey, 4th of july IS fun !!! ;)

PS: not having the amp in my bench, I can't trace those red and black wires, but colour, thickness and spade terminals make me suspect they are the connectors for the mising battery.
I suspect you will measure from 13 to 15 V DC across them, a battery charging voltage.
Check it and post results.
And .... you'll need a new tweeter :(

indianajo 29th January 2013 04:53 PM

If you suspect speaker problems, you need to read the resistance across them. Not near the standard 4 or 8 ohms, or higher for a tweeter, you need to buy something else. At the 20 year boundary, the "crossover" components between the two speakers, particularly any non-polar electrolytic capacitors, are also suspect. Any replacement speaker needs to be near the same resisatance as the original, ie don't put 4 ohm woofers in cabinets designed for 8 ohms.

thuzmund 29th January 2013 08:00 PM

Thanks for the quick replies guys...lot of people seem to be telling me not to play with the junk I find :) But I like to play! You guys are gonna think I'm an idiot for sharing this: when I was 12 or 13, my friend and I took apart an electric lawnmower engine. My friend thought it would be funny to press the start button while we were fooling with it. Shocked me like hell! So we would find ways to trick each other into getting shocked with that thing for a a month or so (putting the wires on a chair, putting it on a baking sheet, etc.) before turning it into a spinning blade of death. So let it be known I'm retarded. Haha I hereby absolve you all of any liability :)

Here's a response from the company that made the unit, for posterity:

"Your unit requires good batteries to function properly. The power cord supplies barely enough current to turn the unit on and charge the batteries.

When the batteries are worn out and the speaker is required to put out high levels of audio, the batteries will sag resulting the in the unit powering off. With the power switch in the off position, the charge indicator (top light ) should be flashing indicating fully charged batteries, however the battery monitoring circuit is actually measuring the charge voltage. If you disconnected the batteries with the power switch off, the light will still flash fully charged. Your unit needs two new batteries. They can be found locally since they are not proprietary (used in alarm systems and emergency lights ).

Your high frequency driver should only have two wires connected to it. Any additional speaker should be connected to the speaker out jacks."

JMFahey, I will take a peek and see where that missing battery might fit in...also check Voltage as you suggest and post. Still at work for a few more hours.


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